PETS ARE PATIENTS TOO: A REVIEW OF VETERINARY COMPOUNDING
Faculty:
Liz Fredrickson, PharmD, BCPS
Liz Fredrickson is an Associate Professor of Pharmacy Practice and Pharmaceutical Sciences at the Northeast Ohio Medical University (NEOMED) College of Pharmacy, where she is course director of the Parenteral Products and Basic Pharmaceutics Lab courses.
Pamela Sardo, PharmD, BS
Pamela Sardo is a freelance medical writer and licensed pharmacist. She is the founder and principal at Sardo Solutions in Texas. Pam received her BS from the University of Connecticut and her PharmD from the University of Rhode Island. Pam’s career spans many years in retail, clinics, hospitals, long-term care, Veterans Affairs, and managed health care responsibilities across a broad range of therapeutic classes and disease states.
Abstract
Pharmacists are uniquely positioned among healthcare professionals to support medication-related care for human and veterinary patients. Despite the significant need for veterinary medications, there remains a limited availability of FDA-approved drug products specifically designed for many animal species. Compounded medications help address this therapeutic gap and play an important role in supporting the health and well-being of veterinary patients. However, providing veterinary compounding services requires pharmacists and pharmacy technicians to possess not only strong compounding skills but also an understanding of species-specific pharmacokinetic, physiologic, and formulation considerations that may affect medication safety and efficacy. This course reviews the benefits and risks of veterinary compounding, current regulatory and legal considerations, common veterinary dosage forms, and key factors in preparing safe and effective compounded medications for animal patients.
Accreditation Statements
In support of improving patient care, RxCe.com LLC is jointly accredited by the Accreditation CouncilTM for Continuing Medical Education (ACCME®), the Accreditation Council for Pharmacy Education (ACPE®), and the American Nurses Credentialing Center (ANCC®), to provide continuing education for the healthcare team.
Joint Universal Activity Number: The Joint Accreditation Universal Activity Numbers assigned to this activity are as follows:
Pharmacists: JA4008424-0000-26-069-H07-P
Pharmacy Technicians: JA4008424-0000-26-069-H07-T
Credits: 2 contact hour(s) (0.2 CEU(s)) of continuing education credit.
Credit Types:
Pharmacy - 2 Credits
Type of Activity: Knowledge
Media: Computer-Based Training (i.e., online courses)
Estimated time to complete activity: 2 contact hour(s) (0.2 CEU(s)), including Activity Pre-Test, Post-Test, and Activity Evaluation.
Release Date: May 19, 2026 Expiration Date: May 19, 2029
Target Audience: This educational activity is for Pharmacists and Pharmacy Technicians
How to Earn Credit: From May 19, 2026, through May 19, 2029, participants must:
Read the “learning objectives” and “author and planning team disclosures;”
Take the “Educational Activity Pre-Test;”
Study the section entitled “Educational Activity;” and
Complete the Educational Activity Post-Test and Activity Evaluation. The Educational Activity Post-Test will be graded automatically. Following successful completion of the Educational Activity Post-Test with a score of 70% or higher, a statement of participation will be made available immediately. (No partial credit will be given.)
CE or CME Credits: Credits for this course will be uploaded to CPE Monitor® for pharmacists and pharmacy technicians. Physicians may receive AMA PRA Category 1 Credit™️ and use these credits toward Maintenance of Certification (MOC) requirements. Physician Assistants may earn AAPA Category 1 CME credits, reportable through PA Portfolio. All learners shall verify their individual licensing board’s specific requirements and eligibility criteria.
Statement of Need
Veterinary compounding fills the gap when FDA-approved commercial products are unavailable, when marketed strengths or dosage forms are inappropriate for patients, or when they are poorly accepted by patients. Addressing these gaps improves the likelihood of effective treatment and adherence. Regulatory requirements for compounding are complex. There is suboptimal awareness of the need to understand and comply with state and federal rules and laws, and of the appropriate use of veterinary compounding strategies and tips. Purchase and use of bulk substances should occur when appropriate and require familiarity with proper storage, proper use, and knowledge of which ingredients can safely be combined. Skills are required to understand and assess differences in absorption, distribution, metabolism, and elimination of medication from the body. This activity aims to enhance factors associated with species-specific compounding, including consideration of anatomy and species behavior, to optimize the approach to care. Compounding professionals are expected to select safe dosage forms, flavors, excipients, and delivery systems for diverse animal patients. This activity strives to avoid treatment failures or toxicity in the provision of care.
Learning Objectives: Upon completion of this educational activity, participants should be able to:
Identify the benefits of compounding for veterinary patients
Explain regulatory and legal considerations when compounding for veterinary patients
Describe dosage forms that may be compounded for veterinary patients
Describe important pharmacokinetic, physiologic, and formulation considerations when compounding for veterinary patients
Disclosures
The following individuals were involved in planning, developing, and/or authoring this activity: Liz Fredrickson, PharmD, BCPS; and Pamela Sardo, PharmD, BS. None of the individuals involved in developing this activity has a conflict of interest or financial relationships related to the subject matter. There are no financial relationships or commercial or financial support relevant to this activity to report or disclose by RxCe.com or any of the individuals involved in the development of this activity.
© RxCe.com LLC 2026: All rights reserved. No reproduction of all or part of any content herein is allowed without the prior, written permission of RxCe.com LLC.
Educational Activity Pre-Test
Which of the following reflects a current regulatory consideration in veterinary compounding practice?
USP <795> and <797> revisions became enforceable in 2023
Veterinary compounding is exempt from all USP standards
Bulk drug substances are unrestricted in veterinary compounding
FDA-approved drugs can never be used in veterinary compounding
Why should xylitol-containing formulations generally be avoided in dogs?
Dogs poorly absorb xylitol
Xylitol may cause severe hypoglycemia in dogs
Xylitol reduces oral bioavailability
Dogs strongly dislike sweet flavors
A geriatric cat with chronic kidney disease refuses bitter oral tablets and often vomits. The veterinarian wants to improve acceptance and maintain accurate dosing. Which compounded dosage form could most likely be tried first?
Intranasal solution
Hard capsule
Flavored oral suspension
Medicated transdermal cream
Educational Activity
Pets Are Patients Too: A Review of Veterinary Compounding
Highlights Pharmacists are uniquely positioned to support medication-related care for both human and veterinary patients, including preparing customized compounded medications for a wide variety of animal species. Veterinary compounding is often necessary because many FDA-approved medications are unavailable in appropriate strengths, dosage forms, or flavors for animal patients. A valid veterinarian-client-patient relationship (VCPR) is essential before compounded medications are prepared for veterinary patients. Species differences in metabolism can dramatically affect medication safety. Drugs considered safe in humans may be toxic or fatal in animals. Compounded veterinary preparations may pose risks, including contamination, instability, inaccurate potency, and poor bioavailability, if appropriate compounding standards are not followed. Flavoring agents, sweeteners, and excipients used in veterinary compounds must be carefully selected because ingredients safe for humans may be harmful to certain animal species. |
Introduction
Pharmacists may provide care for human and veterinary patients, placing them in a unique position within healthcare. In veterinary medicine, pharmaceutical compounding plays a critical role in helping meet the individualized needs of animal patients when commercially available medications are unavailable or inappropriate. Pharmacists and pharmacy technicians involved in veterinary compounding should understand the benefits, risks, regulations, and species-specific considerations associated with compounded preparations. Importantly, medications that are safe and effective in humans may behave very differently in animals due to significant variations in anatomy, physiology, metabolism, and drug elimination among species. As a result, compounding for veterinary patients requires careful consideration of pharmacokinetic principles, formulation characteristics, and the unique needs of each animal patient.
Veterinary Compounding: An Overview, Benefits, and Risks
Among healthcare providers, pharmacists are uniquely positioned to support medication-related care for both human and animal patients.1 Despite being well-trained in pharmacotherapy, pharmaceutical compounding, and drug delivery, the majority of graduating student pharmacists receive little to no education on these topics as they pertain to animals.2 This is significant because pharmacists are becoming increasingly involved in animal care within the United States (US).2,3 Their roles include the provision of compounded medications to meet the unique and individual needs of veterinary patients.4 Depending on the pharmacy setting, pharmacists may have opportunities to compound medications for a number of different animal species, including companion pets (such as cats, dogs, and ferrets), pocket pets (small animals such as hamsters and gerbils), work animals (horses and oxen), and even zoo and exotic animals.4 The term “patient” refers to the animal or pet, while “client” refers to the pet owner.
Currently, there is a limited availability of FDA-approved drug products specifically designed for veterinary species, despite the substantial and growing need for animal medications.5 Compounded preparations help address this therapeutic gap, and veterinary compounding plays an important role in supporting the health, safety, and well-being of animals.5 The American Veterinary Medical Association (AVMA) has emphasized the value of compounding, stating that “Compounding is a needed tool and provides much-needed therapeutic flexibility for veterinarians, especially considering the wide range of species and breeds veterinarians treat.”6
In 2015, the Food and Drug Administration (FDA) estimated 75,000 pharmacies compounded a total of 6,350,000 prescriptions for animals in the US.7 The FDA defines animal drug compounding as the process of combining, mixing, or altering ingredients to create a medication tailored to the needs of an individual animal or a small group of animals.8 Compounding does not include the mixing, reconstituting, or other such acts that are performed in accordance with directions contained in approved labeling provided by the manufacturer, directions consistent with that labeling.8 Pharmacists and pharmacy technicians should be familiar with the circumstances under which compounding is deemed appropriate. These include when:
Manufactured medications have been recalled or are under a drug shortage
A patient is allergic to or does not tolerate specific ingredients within a manufactured medication
A patient requires a different strength or dosage form of medication
Flavoring or sweetening agents need to be added to a medication to make it more palatable.8,9
Additional reasons to compound for veterinary patients are listed in Table 1.
Table 1
Reasons to Compound for Veterinary Patients9,10
| When there is a need for rapid changes in the management of disease problems in veterinary medicine |
| When there is a need to achieve an appropriate treatment regimen for the species, age, or size of the animal patient |
| When problems associated with the treatment of a large number of animals with several drugs in a short period of time arise |
| When there is a desire to achieve an additive therapeutic effect when administering two or more products at the same time |
| When there is a need to combat multiple and concurrent disease processes |
| When there is a need to minimize suffering, harmful stress, and mortality in animals |
Conversely, there are several reasons why it is inappropriate to compound for veterinary patients. One of the most important is a lack of a veterinary client-patient relationship (VCPR).11 A VCPR is a relationship in which the veterinarian is intimately familiar with the animal patient and is thereby able to diagnose and treat their medical conditions, and the client asks the veterinarian questions and follows instructions.11 Other reasons include:
The availability of an FDA-approved product, compounding for use in food animals
Mass manufacturing
Compounding from bulk active pharmaceutical ingredients when approved products exist
To decrease cost
To make a copy of a commercially available drug.9,11
The responsibilities of both veterinarians and pharmacists in compounding are detailed in Table 2 below. Finally, it is important for pharmacists to establish well-working relationships with prescribing veterinarians prior to engaging in veterinary compounding. In this way, the pharmacist and veterinarian can work together to determine the best course of action for medication therapy in animal patients.9
Table 2
Responsibilities of Veterinarians and Compounding Pharmacists12
| Veterinarian Responsibilities | Compounding Pharmacist Responsibilities |
| Assess whether an FDA-approved, conditionally approved, or indexed veterinary or human medication is available and clinically appropriate | Evaluate whether compounding is necessary or if a commercially available product can adequately meet the patient’s needs |
| Provide patient-specific clinical information that may affect formulation selection, administration, safety, or therapeutic response | Determine whether compounding from a bulk drug substance is appropriate and compliant with current regulatory guidance |
| Collaborate with the pet owner to determine the most appropriate therapeutic option for the animal | Ensure legal and regulatory requirements are met when using bulk drug substances or preparing office stock |
| Review available scientific literature and evidence regarding compounded preparations when possible | Select appropriate excipients, dosage forms, flavors, and delivery systems based on species-specific considerations |
| Monitor the patient closely for therapeutic response, treatment failure, or adverse reactions | Assess formulation stability, compatibility, quality, and likelihood of safe and effective drug delivery |
| Identify measurable clinical outcomes to evaluate treatment effectiveness and safety | Assign an appropriate beyond-use date (BUD) and recommend proper packaging and storage conditions |
| Educate the client regarding the potential risks, benefits, and limitations of compounded medications | Ensure compounded products are accurately labeled with directions, warnings, and precautionary information |
| Obtain informed consent from the client regarding the use of compounded medications | Counsel pet owners or caregivers regarding administration, storage, handling, and beyond-use dating |
| Recommend a reputable and qualified compounding pharmacy | Communicate with the veterinarian regarding formulation concerns, potential risks, and therapeutic considerations |
| Report suspected adverse events or treatment failures to the compounding pharmacy and appropriate regulatory agencies | Report adverse events or product quality concerns to the appropriate regulatory agencies when necessary |
| Assist in ensuring compliance with Drug Enforcement Administration (DEA) requirements when controlled substances are involved |
Compounding Benefits for Veterinary Patients
Compounded medications can benefit veterinary patients in many of the same ways they benefit human patients. Some of the most common benefits are described below.5
1) Provision of unavailable medications
If no FDA-approved drug product exists for a specific species, or if these products have been recalled or are under a drug shortage, compounding pharmacists may compound these medications for veterinary patients.5 This can benefit veterinary patients and their owners, and in some cases, it can be life-saving for the pet.
2) Provision of a needed dosage form or medication strength
FDA-approved products are often available but only in a dosage form deemed inappropriate for a specific species or breed. In these cases, pharmacists can compound the required dosage form or strength of the medication.5,8 For example, a large-sized chewable treat would not be appropriate for use in a small cat.5 Similarly, while levothyroxine is available in various strengths, a dog will require a much higher number of tablets than a human patient, potentially precluding adherence to therapy. The intended dosage form may also be created to benefit the pet owner as much as their pet. For example, cats do not prefer to take medications in pill form.5 In some cases, medications can instead be formulated as transdermal applications, providing ease of administration to owners who have difficulty getting their cat to take a pill.5,13
3) Provision of a flavored form of a medication
Medications that are not flavored or sweetened to mask bitterness or cover challenging tastes will likely not be acceptable to veterinary patients.5 Animals tend to prefer flavors that mimic their natural diets.9 For example, cats prefer a fish or tuna flavor over the bubblegum or citrus flavors of commercially available products.9 Pharmacists provide an important service by selecting appropriate flavors (or flavor blends) to ensure pet adherence to therapy.
Compounding Risks for Veterinary Patients
While compounded medications provide numerous benefits for pets, they are not without associated risks. When extreme care and attention are not taken when preparing compounded veterinary medications, pets are placed at significant risk of harm, which can range from not receiving a therapeutic benefit to experiencing toxicities and adverse reactions.5 It has been noted that there is even less regulatory oversight of veterinary compounding compared to that of human compounding.5 The following errors may occur when compounding for veterinary patients:5
Error in preparation, due to compounding technique or inappropriate formulations
Contamination of the preparation
Chemical or physical instability of the preparation
Little to no bioavailability of the preparation in the target patient
The Missouri State Board of Pharmacy found that 20% of compounds reviewed from Missouri-licensed pharmacies contained an incorrect amount of the active ingredient, ranging from 0% to 45% of the amount indicated on the prescription label.5 Unfortunately, there is little legal requirement requiring tests to demonstrate that a compounded preparation meets the strength indicated on the label. A large amount of data shows compounded preparations are not bioequivalent to manufactured products.5 As one example, veterinary medications are often prepared as transdermal formulations; however, drugs administered via this route lack the bioavailability of their oral counterparts.5
Veterinary Compounding Rules, Regulations, and Oversight
Pharmacists should thoroughly understand USP standards and the rules and regulations surrounding veterinary compounding. The United States Pharmacopeia (USP) offers guidance pertaining to the preparation of nonsterile (USP <795>) and sterile (USP <797>) compounded preparations. These chapters were officially revised in 2023 and provide current standards for nonsterile and sterile compounding practices.14,15 USP also offers verified, reviewed monographs, around 20 of which relate to veterinary preparations.9 Additionally, various USP chapters are relevant to veterinary compounding, including those focused on stability, quality assurance, calculations, prescription balances, and volumetric apparatus.9
In addition to following USP guidelines, pharmacists should always refer to the laws and regulations of their local regulatory jurisdiction. In terms of legality, the Federal Food, Drug, and Cosmetic Act (FD&C Act) permits pharmacists to compound medications for veterinary patients when the active ingredient is sourced from an FDA-approved drug.8 Under federal law, veterinarians and pharmacists generally should use FDA-approved animal or human drugs when medically appropriate and available. However, FDA guidance outlines circumstances in which compounding from bulk drug substances may be appropriate for an animal patient.8 If there is no medically appropriate drug, a compounded preparation may be prepared from a bulk drug substance.8
In April 2022, the FDA issued guidance on this issue, under “Compounding Animal Drugs from Bulk Drug Substances.”8 Through this report, the FDA sought to ensure veterinarians would have access to drugs to treat their patients while making sure animals and humans would be protected from unsafe animal drugs.8 Importantly, Congress passed the Drug Quality and Security Act in 2013. While this increased regulation of compounding for human patients, it does not cover compounding for veterinary preparations.16
General Veterinary Compounding Checklist17
Confirm whether the patient is a:
Nonfood-producing animal
Food-producing animal
Free-ranging wildlife species
Verify the existence of a valid veterinarian-client-patient relationship (VCPR)
Follow all applicable:
State board of pharmacy laws and regulations
Federal FDA regulations
USP compounding standards
Ensure ingredients meet applicable USP-NF standards when available
Evaluate whether an FDA-approved animal or human drug product can appropriately meet the patient’s needs before compounding
Confirm that compounding is clinically appropriate and not solely for convenience or cost reduction
Include the following on the compounded preparation label:
Drug name and strength/concentration
Species and patient identifier
Prescribing veterinarian information
Compounding pharmacy information
Beyond-use date (BUD)
Appropriate administration directions
Required cautionary statements
Document:
Formula and calculations
Ingredients and lot numbers
Beyond-use date rationale
Compounding procedure
Quality assurance checks
Maintain records of:
Veterinary rationale for compounded copies of FDA-approved products
Reasons approved products could not be used when applicable
Veterinary Compounding Considerations
Pause and Ponder How might species-specific pharmacokinetic differences influence your approach to selecting ingredients, dosage forms, and excipients when compounding medications for veterinary patients? |
Pharmacokinetic Considerations
Pharmacists who compound medications for veterinary patients need to be familiar with the pharmacokinetic properties (absorption, distribution, metabolism, elimination) of various species. These properties can vary widely among species, leading to differences in drug bioavailability and elimination rates.13 Factors, including the dose, formulation, route of administration, the extent of distribution, plasma protein binding, and rate of elimination, can all affect the ultimate concentration of the drug in the plasma.9,13 Pharmacokinetic differences can not only change the effectiveness of any particular preparation but also cause potential toxicities as well.13
Absorption
Absorption is defined as the movement of a drug from its site of administration into the patient’s systemic circulation.13 Current data suggest there are no great differences in the cell membrane chemical composition between different species.13 Absorption differences are most important with regard to specific factors, including the anatomy of animals (their length of GI tract).13 Notably, differences in GI tract length can vary significantly even within a species (for example, a Great Dane compared to a Chihuahua).13 Other factors include physiological differences (such as pH differences in the GI tract and gastric emptying times) and differences in the availability of drug transporters, such as P-glycoprotein.13 As an example of the impact of absorption, a sustained-release preparation of medication useful for humans would be less helpful for animals because of their differences in gastric pH and often shorter intestines.13
Distribution
Drug distribution is the movement of drugs from the patient’s systemic circulation to their site of action (i.e., tissues).13 It is a significant factor and contributes to pharmacokinetic differences between species.13 The distribution of drugs depends on many factors, including blood flow to tissues, relative tissue mass, plasma protein binding, and tissue barriers to distribution.9,12 Because animals have different body compositions, the distribution of drugs to their target sites will differ greatly.9 Table 4 details variations in body composition among different animal species.9
Table 4
Variations in Body Composition
Among Selected Animal Species9,10
| Anatomical Component | Human (%) | Horse (%) | Dog (%) |
| Blood | 7.8 | 8.6 | 7-9 |
| Brain | 2.0 | 0.2 | 0.5 |
| Heart | 0.5 | 0.7 | 0.8 |
| Lungs | 0.9 | 0.9 | 0.9 |
| Kidney | 0.4 | 0.4 | 0.6 |
| GI tract | 1.4 | 12.7 | 0.7 |
Metabolism
Metabolic differences among animal species are one of the most significant contributors to variation in drug response.13 These differences help explain why medications considered safe in humans may cause severe toxicity or even death in veterinary patients such as cats and dogs.13 One well-known example involves cats, which have a limited capacity for glucuronidation. As a result, medications that rely on glucuronide metabolism, such as aspirin, may accumulate and become toxic in feline patients.9 Other drugs and excipients that undergo similar metabolic pathways may also pose substantial risks to cats.13 This highlights the importance of carefully evaluating every ingredient in a compounded preparation, including excipients, preservatives, dyes, and flavoring agents, before use in a specific species. Cats may also be particularly sensitive to alcohols, benzoic acid derivatives, and azo dyes used in some formulations.13 Because of these species-specific metabolic limitations, pharmacists should thoroughly review formulation components prior to compounding medications for feline patients.
Other examples of metabolism include the absence of acetylation in dogs.12 Further, many dogs also have significant genetic anomalies, which can result in toxicities related to certain compounds.13 A common example is xylitol, which is found in commercially available gabapentin solutions. When a dog ingests xylitol, the pancreas releases insulin, which can result in severe and possibly fatal hypoglycemia.13 Dogs with chronic exposure to xylitol may end up with severe hepatic necrosis.13 Pharmacists should review the ingredients of commercially available products before dispensing such products to canine pet owners.
Elimination
While renal function is similar among mammals, important differences exist. For example, cats concentrate urine to a greater extent than dogs. Urinary differences in pH also exist.13 Herbivores have more alkaline urine, and carnivores tend to have more acidic urine concentrations.9 These differences may account for differences in renal elimination to an extent.13
Physiologic Considerations
When compounding for humans, pharmacists consider unique physiological factors for each patient, and the same process applies to veterinary preparations. Factors such as age, sex, pregnancy status, and the presence of comorbidities should be considered before compounding.9,13 Other considerations include drug or food allergies and the potential for drug-drug interactions.13 For some species, such as cats, the animal's normal behavior must also be considered.9 Cats spend significant time grooming themselves; thus, topical medications are likely to be ingested, and this should be considered in determining the best dosage form and route of administration.9
Formulation Considerations
USP provides numerous official formulas for veterinary patients. A list of some of these official formulas is detailed in Table 5.9 Pharmacists should be cautious not to immediately translate the use of a formulation intended for a human patient to a veterinary patient.9 Non-veterinary monographs can be used for animals, but these must undergo a thorough evaluation to determine safety and effectiveness and to ensure they meet both patient and species-specific criteria.13 In addition to USP, formulations can also be found in the International Journal of Pharmaceutical Compounding and Trissel's Handbook of Injectable Drugs.9 If no formulation has been identified, it is best to work directly with the veterinarian to determine the appropriate formulation.
As discussed, pharmacists may compound for veterinary patients when no effective, FDA-approved product exists. In determining the appropriate formulation, pharmacists need to consider the following as they pertain to the patient: the animal’s size, anatomy, safety, sensitivities or allergies, stress or suffering that can result from administration of large volumes, potential danger to pet or animal owners who must restrain the animal to administer medication, and the potential to minimize side effects and maximize the effectiveness of the therapy.9
Table 5
Official Veterinary Formulas within USP9
| Atenolol Compounded Oral Suspension, Veterinary |
| Benazepril Hydrochloride Compounded Oral Suspension, Veterinary |
| Buprenorphine Compounded Buccal Solution, Veterinary |
| Cisapride Compounded Injection, Veterinary |
| Doxycycline Compounded Ophthalmic Solution, Veterinary |
| Famciclovir Compounded Oral Suspension |
| Pergolide Oral Suspension, Veterinary |
| Tadalafil Compounded Oral Suspension |
| Zonisamide Compounded Oral Suspension |
Pharmacists should also ask themselves several questions to ensure they compound in a legal, effective, and safe manner. The following questions should be asked:9
What is known about the physical and chemical compatibility of the drugs?
What is known about the stability of the drugs?
What is known about the pharmacodynamic compatibility of the active ingredient?
What is the overall goal of treatment?
Are similar products available commercially to treat the animal?
Is the animal a food animal?
Will the drug treatment cause a residue problem?
Is there a risk to personnel who handle the drug during compounding or during the administration of the compounded preparation?
Excipients
Not only does the active pharmaceutical ingredient need to be considered within a compounded preparation, but excipients (added substances) do as well.9 Excipient concerns range from eliciting allergic reactions or intolerances to causing serious toxicities and even death. Table 6 details excipients, foods, and drugs that are harmful to various species.18-23
Table 6
Toxic Excipients and Foods by Species18-23
| Food or Excipient | Species Affected | Toxicity |
| Benzyl alcohol | Cats | Methemoglobinemia |
| Azo dyes | Cats | Methemoglobinemia |
| Propylene glycol | Cats | Hemolytic anemia |
| Ethanol | Dogs | Ataxia, coma, respiratory depression |
| Xylitol | Dogs | Hypoglycemia, hepatocellular necrosis |
| Polysorbate 80 | Dogs | Anaphylaxis |
| Chocolate | Dogs | CNS stimulation, seizures, coma |
Routes of Administration and Dosage Forms for Veterinary Patients
The same routes of administration used for humans are also used for animal patients. In addition, many devices are available to assist with administering medications to pets and other animals. Numerous dosage forms can be compounded for veterinary patients, and pharmacists should be skilled in preparing boluses, chewable treats, capsules, oral pastes, gels, and topical formulations. This section will detail the oral, topical, transdermal, parenteral, and nasal routes of administration and associated dosage forms.
Oral Route
The oral route of administration is commonly used to administer compounded medications to veterinary patients.9 This route is normally meant to induce systemic effects, but in some cases can be used for local effects (such as with kaolin).16 By compounding oral preparations, pharmacists can adjust the dose, flavor, and/or concentration of commercially available products.9 The oral route is associated with some disadvantages, in that there is a slow onset of action and the possibility of irregular absorption.9 In formulating oral preparations, pharmacists need to take special care.9
Examples of oral dosage forms include tablets, capsules, liquid preparations, such as suspensions and solutions, pastes, and chewable treats.15 Oral liquids may be preferred as they are easier to administer than tablets and capsules, especially for cats.9 When preparing a suspension, particle size and viscosity should be considered. Useful suspension bases include methylcellulose and simple syrup.13 The use of silica gel as a suspending agent should be avoided in animals that could develop silicate uroliths.12
Oral pastes are also commonly prepared for veterinary patients.9 These compounds have a high viscosity and are useful for animals that have the propensity to allow medications to run out of their mouths.13 Pastes can also be applied to cats' limbs, where they are licked and ingested.16 Chewable (medicated) treats are also popular.9 These dosage forms are familiar to pets and can be made for dogs, cats, ferrets, and other species. They are often prepared using pet food as the base.9 Clients should be counseled to store chewable treats out of reach to avoid overdose in the pet.
Formulation Example
Chewable treats are a common formulation prepared for pets, and an example of a chewable treat base formulation is provided below (Table 7).9
Table 7
Chewable Treat Formulation Example
| Ingredient | Quantity | Purpose |
| Animal food base | 65 grams | Vehicle |
| Gelatin base, melted | Qs 100 grams | Binder |
| Active drug | Qs | Active ingredient |
Steps:
Calculate the quantity of each ingredient required for the preparation
Accurately weigh or measure each ingredient
Pulverize a nugget-type animal food of choice
Melt the gelatin base
Incorporate the powdered animal goods and mix well
Add the active drug and mix well
Pour the mixture into molds and allow it to set
Package and label the product
Devices for Oral Administration
As with pediatric patients, administering medications to veterinary patients by the oral route can be difficult and stressful for both the animal and the caregiver. Many animals resist oral medications due to unfamiliar tastes, odors, or textures, or to fear or discomfort associated with handling and restraint. As a result, veterinarians and pharmacists should consider not only the formulation itself but also the practicality and ease of administration for the owner or handler.
To improve medication delivery and adherence, a variety of devices have been developed to assist with oral administration in veterinary patients.9 These devices may help ensure accurate dosing, reduce stress during administration, improve patient safety, and enhance treatment success. Table 8 highlights commonly used devices for oral medication administration in veterinary medicine.9
Table 8
Devices for Oral Administration
| Device | Description |
| Balling gun | Has a barrel through which a plunger passes that is capable of dislodging a bolus into the gut of an animal |
| Buoyant device | Resemble large, floating tables and allow the dosage form to float in the intestine and release the medication over an extended period of time |
| Drench syringe | Single or multiple dose devices capable of delivering preset volumes of liquid into the gullet |
| Esophageal delivery | Syringes and tubes that are usually designed to deliver medication directly into the stomach |
| Hollow bits | A hollowed-out area in which medications that have a heat-sensitive matrix are placed |
| Liquid drench guns | Single or multiple dose devices capable of delivering oral solutions or suspensions of an aqueous or oily nature quickly |
| Paste dispensers | Include paste guns, paste syringes, squeeze bottles, and squeeze tubes that are capable of delivering a specified dose to an animal |
| Oral dosing syringe | Allow liquids to be measured accurately and administered cleanly |
| Powder drench guns | Spring-loaded devices capable of delivering required amounts of powder into the back portion of the mouth |
| Rumen-lodging devices | Incorporated into medications that have a controlled-release delivery system |
| Water medication-metering devices | Method of adding medication to the water supply of numerous animals |
| Miscellaneous oral dose dispensers | Droppers, mineral dispensers, mouthpieces, nurses, pump-type dispensers |
Topical Route
Topical administration allows treatment of localized skin infections and control of parasites.16 Examples of topical dosage forms include semisolids (ointments, creams, and pastes), dusting powders, and suspensions and solutions.16 Formulations such as foams, shampoos, and rinses are commonly used to treat parasites and ticks. The semisolid base used is an important consideration in determining the rate of drug release from the topical preparation.16
Many devices are used to prevent or remove lice and fleas from animals and to treat skin conditions. Table 9 details available topical devices.9
Table 9
Devices for Topical Administration9
| Device | Description |
| Aerosol dispensers | Convenient way to apply medications |
| Dust bags | Used to apply powders to cattle as they brush up against or walk underneath the bags |
| Flea and tick collars | Use slow-release generators containing medications that either have a high vapor pressure or are designed as a solid solution so the product will migrate from the collar over the body |
| Percutaneous absorption drug reservoir devices | Drug-containing matrices that allow the drug to diffuse from the device into the animal’s skin or onto the skin surface |
| Pour-on, spot-on applications | Used to treat skin conditions or surface conditions of animals |
| Spray race and dip | Long troughs with deep sides that are commonly used for dipping treatments |
| Teat dip applicators | Immerse the animal completely without injuring it |
Transdermal Route
The transdermal route is an important means of administering various medications to veterinary patients. Transdermal gels are more complex compounded preparations that involve penetration-enhancing percutaneous vehicles (such as PLO) to achieve the bioavailability needed for medication efficacy.9,13 Veterinarians will often consult pharmacists to see if they can compound a medication as a transdermal formulation.11
Unfortunately, only a limited number of medications can be prepared as transdermal formulations. Major considerations in determining whether an active ingredient can be delivered via the transdermal route include the drug's molecular weight (MW > 300 Daltons precludes this route), therapeutic index, and lipid solubility.9,13 Lipid solubility improves the absorption of transdermal formulations. Drugs with large molecular weights, poor lipid solubility, narrow therapeutic indices, and known human safety issues should not be prepared as transdermal formulations.13
A commonly compounded transdermal formulation is methimazole gel, used to treat hyperthyroidism in cats.13 Below (Table 10) is an example of a transdermal formulation for methimazole 5 mg/0.1 mL in PLO.9
Table 10
Methimazole Transdermal Formulation Example9
| Ingredient | Quantity | Purpose |
| Methimazole | 150 mg | Active ingredient |
| Lecithin: isopropyl palmitate 1:1 solution | 0.66 mL | Emulsifier |
| Pluronic F-127 20% gel | Qs 3 mL | Vehicle |
Steps:
Calculate the quantity of each ingredient required for the prescription
Accurately weigh or measure each ingredient
Remove the plunger from a 3-mL luer lock syringe and attach a tip cap
Pour methimazole powder carefully into the syringe barrel
Add lecithin: isopropyl palmitate 1:1 solution and replace the plunger
In the second syringe, measure 2 mL of the Pluronic F-127 20% gel
Attach a Luer-Lok/Luer-Lok adapter to fit the syringes together and mix contents back and forth between the two syringes
Carefully force all the preparation into one syringe and measure the volume
Remove the other syringe and obtain sufficient gel to the volume
Reattach the syringes and mix the preparation back and forth until it is thoroughly mixed
Package and label the preparation
Table 11 lists examples of medications that may be compounded as transdermal formulations.9
Table 11
Medications Able to be Compounded
as Transdermal Formulations9
| Aminophylline |
| Amitriptyline |
| Azithromycin |
| Buspirone |
| Chloramphenicol |
| Digoxin |
| Doxycycline |
| Enrofloxacin |
| Glipizide |
| Phenobarbital |
| Prednisolone |
Parenteral Route
Drugs that are administered parenterally are given via a route other than the mouth (or topically).15 Example routes include intramuscular (IM), subcutaneous (SC), and intravenous (IV). These dosage forms must be prepared using aseptic technique in a sterile environment. Parenteral administration is often a useful means of administering medications to animals, especially when they need to be given from a safe distance.8 The following devices are used for the parenteral administration of medications to veterinary patients (Table 12).9
Table 12
Parenteral Administration of Medications9
| Device | Description |
| Single-dose syringes | Used to treat one animal at a time; can be disposable syringes or ones that can be resterilized |
| Multiple-dose syringes | Used to treat small herds when an automatic syringe is not required; contains several doses |
| Automatic syringe | Used to treat large herds |
| Multi-compartment syringe | Used for unstable drug products requiring the addition of a diluent |
| Pole-mounted syringes | Allow medications to be administered safely from a distance |
| Mastitis syringe | Used to insert a drug formulation directly into the mammary gland |
| Implants | Sterile dosage forms are designed so that a depot of the drug can be placed at a site in the body for prolonged release of the drug |
Nasal Route
When medications are administered via the nasal route, the onset of action is nearly the same as with parenteral administration.9 Nasal administration is preferred over parenteral administration in some cases, as it does not involve piercing and avoids some of the risks of parenteral administration.9 Examples of medications administered via the nasal route are vaccinations and antibiotics.9 Dropper dispensers and spray dispensers are devices usually to deliver medications nasally.
Pause and Ponder What steps can pharmacists and pharmacy technicians take to improve the safety, quality, and effectiveness of compounded medications for veterinary patients in their practice setting? |
Flavoring and Texture Considerations
Selecting a flavor for a medication that is appealing to the animal without compromising the preparation's stability or safety is critical.9 The addition of a flavoring agent should not alter drug bioavailability, solubility, or suspendability.12 In general, animals prefer flavors that mimic their normal diet. Birds tend to prefer sweet and fruity flavors.9 In addition to flavor preferences, birds may also have texture preferences to consider. For example, certain birds prefer movement (such as a wiggly worm) over a particular flavor.9,13 Dogs are omnivores who prefer meat and sweet flavors.9,13 Fixed oils are a great option for canines. Cats, due to a lack of sweet taste receptors on their tongues, do not prefer sweet flavors and also find bitter tastes disagreeable.25 They do better with flavors such as tuna, liver, or marshmallow.9,13 Ferrets often prefer meat and fish flavors, but also enjoy sweet flavors. Gerbils like sweet and fruity flavors, while guinea pigs prefer vegetable-flavored preparations. Finally, rabbits prefer herb, vegetable, or fruit flavors.9,13
Clinical Pearl Cats lack functional sweet taste receptors, making fish- and meat-based flavors more acceptable than sweet flavoring systems. |
Table 13 details flavoring considerations for common animal species. Pharmacists should also always consult the pet owner to determine any specific flavor preferences. A number of companies provide liquid and powder flavoring agents for pets as well as flavored bases. Dogs and ferrets, in particular, prefer the taste of oil, and using an almond- or similar oil in a preparation provides a neutral, palatable taste for these species.11
Table 13
Flavor Preferences of Selected Species9
| Animal | Suggested Flavors |
| Birds | Banana, grape, honey, millet, orange, nectar, tutti-frutti |
| Dogs | Bacon, beef, liver, chicken, turkey, cheese, chocolate (artificial), peanut butter, cod, anise, marshmallow |
| Cats | Fish, liver, tuna, cod liver oil, chicken, cheese, bacon, molasses, butterscotch, marshmallow |
| Ferret | Chocolate, peanut butter, molasses, honey, fish, fruit punch, strawberries, peas |
| Gerbil | Banana cream, orange, peach, tangerine, tutti-frutti |
| Guinea pig | Carrot, celery, lettuce, pumpkin |
| Rabbit | Banana cream, carrot, celery, lettuce, parsley, pineapple, vanilla butternut |
In addition to flavoring medications, pharmacists should also consider how best to sweeten their preparations. The following sweeteners (and recommendation concentrations) can be used in veterinary preparations.25
Table 14
Sweeteners for Veterinary Compounds25
| Sweetener | Concentration |
| Acesulfame potassium | 0.1-0.5% |
| Steviol glycosides 95% | 0.1-0.6% |
| Stevioside 15% | 1-4% |
Summary
Among all healthcare providers, pharmacists are the only ones who can care for both human and animal patients. One of the major roles pharmacists play in the care of veterinary patients is compounding medications to meet the individual needs of these animals. Currently, there is limited availability of approved drug products for veterinary species, despite the high demand for veterinary medications.5 While the provision of compounded medications plays a critical role in the health of animals, filling a gap in the lack of manufactured drug products, this service comes with an important responsibility to be knowledgeable and appropriately trained in compounding skills and in the various animal species pharmacists are likely to encounter.
References
Stafford EG. Highlighting the role of veterinary pharmacists in zoonotic diseases including COVID-19. J Am Pharm Assoc (2003). 2020;60(6):e84-e87. doi:10.1016/j.japh.2020.06.021
Theberge CR, Sehgal I. Bringing more veterinary pharmacy into the pharmacy curriculum. Am J Pharm Educ. 2016; 80(5):89. doi: 10.5688/ajpe80589
Ceresia ML, Fasser CE, Rush JE, et al. The role and education of the veterinary pharmacist. Am J Pharm Educ. 2009;73(1):16. doi:10.5688/aj730116
Bennett SA, Ruisinger JF, Prohaska ES, et al. Assessing pet owner and veterinarian perceptions of need for veterinary compounding services in a community pharmacy setting. Pharm Pract (Granada). 2018;16(3):1224. DOI: 10.18549/PharmPract.2018.03.1224
Davidson G. Veterinary Compounding: Regulation, Challenges, and Resources. Pharmaceutics. 2017;9(1):5. Published 2017 Jan 10. doi:10.3390/pharmaceutics9010005
American Veterinary Medical Association. Compounding. (n.d.). Accessed May 12, 2026. https://www.avma.org/KB/Resources/Reference/Pages/Compounding.aspx
Compounding Animal Drugs From Bulk Drug Substances; Draft Guidance for Industry; Availability; Withdrawal of Compliance Policy Guide; Section 608.400 Compounding of Drugs for Use in Animals.
Animal Drug Compounding. US Food and Drug Administration. September 2022. Accessed May 12, 2026. https://www.fda.gov/animal-veterinary/unapproved-animal-drugs/animal-drug-compounding
Allen L. The Art, Science, and Technology of Pharmaceutical Compounding. 6th edition. APhA. 2020.
Cotter S. Blood Transfusions in Animals. MSD Manual. Veterinary Manual. Merck & Co., Inc., Update 2025. Accessed May 12, 2026. https://www.msdvetmanual.com/circulatory-system/blood-groups-and-blood-transfusions/blood-transfusions-in-animals?query=transfusion
Veterinarian-Client-Patient Relationship (VCPR) FAQ. AMVA. Accessed May 12, 2026. https://www.avma.org/resources-tools/pet-owners/petcare/veterinarian-client-patient-relationship-vcpr-faq
Forsythe L. A Veterinarian’s Guide to Compounded Medications. Today's Veterinary Practice. February 12, 2026. March/April 2026 Issue. Accessed March 20, 2026. https://todaysveterinarypractice.com/pharmacology/a-veterinarians-guide-to-compounded-medications/
Mealey, K. Pharmacotherapeutics for Veterinary Dispensing. 1st edition. 2019. Wiley-Blackwell.
General Chapter: USP. Pharmaceutical Compounding-Nonsterile Preparations <795>. In: USP-NF. Rockville, MD: USP; 2023.
General Chapter: USP. Pharmaceutical Compounding-Sterile Preparations <797>. In: USP-NF. Rockville, MD: USP; 2023.
Reeves, P et al. Routes of Administration and Dosage Forms. Merck Manual of Veterinary Medicine. Merck & Co. 2022. Accessed May 2026.
U.S. Food and Drug Administration. For Pharmacists: Compounding Animal Drugs. Undated. Accessed May 10, 2026. https://www.fda.gov/media/157331/download?attachment
Cullison EA. Toxicosis in cats from use of benzyl alcohol in lactated Ringers solution. J Am Vet Med Assoc. 1983;182(1):61.
Christopher MM, Perman V, Eaton JW. Contribution of propylene glycol-induced Heinz body formation to anemia in cats. J Am Vet Med Assoc. 1989;194(8):1045-1056.
Carpenter MM, Hovda LR. Alpha lipoic acid toxicosis in cats (2008-2016): Four cases. J Vet Emerg Crit Care (San Antonio). 2022;32(2):249-253.
Baggott MJ, Childs E, Hart AB, et al. Psychopharmacology of theobromine in healthy volunteers. Psychopharmacology. 2013;228(1):109-118.
U.S. Food and Drug Administration. Inactive ingredient search for approved drug products (search term “xylitol”). FDA. Accessed May 12, 2026. http://www.accessdata.fda.gov/scripts/cder/iig/getiigWEB.cfm
Qiu S, Liu Z, Hou L, et al. Complement activation associated with polysorbate 80 in beagle dogs. Int Immunopharmacol. 2013;15(1):144-149.1
Li X, Li W, Wang H, et al. Cats lack a sweet taste receptor. J Nutr. 2006;136(7 Suppl):1932S-1934S. doi:10.1093/jn/136.7.1932S
Klein, J. Artificial Sweeteners: Which ones are safe for dogs? American Kennel Club. Accessed May 12, 2026. https://www.akc.org/expert-advice/vets-corner/artificial-sweetener-safety-for-dogs/
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The information provided in this course is general in nature, and it is designed solely to provide participants with continuing education credit(s). This course and materials are not meant to substitute for the independent, professional judgment of any participant regarding that participant’s professional practice, including but not limited to patient assessment, diagnosis, treatment, and/or health management. Medical and pharmacy practices, rules, and laws vary from state to state, and this course does not cover the laws of each state; therefore, participants must consult the laws of their state as they relate to their professional practice.
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