Compounding services have become more abundant as veterinary pharmacies multiply and enjoy financial success. Compounded drugs provide veterinarians with a more convenient or accurate dosing form for their animal patients.
The compounding services that pharmacists are offering to veterinarians include:
- reformulation (eg, making solutions from solid dosing forms, making oral dosing forms from injectable products),
- mixing of two or more drugs in a single product, and
- formulation of a drug in a novel delivery system (eg, lecithin organic gels applied topically with the intent of systemic drug delivery, chewable forms, inhalants, medicated biscuits, ophthalmic preparations, otic solutions, rectal suppositories).
When using a compounding pharmacy, however, veterinarians must not outsource their medical judgment. Just because a pharmacy produces a product such as a gel, it doesn't mean the product is safe or effective.
No published scientific data exist to document the proper regimen of a gel product necessary to deliver a safe, yet effective, dose of any drug in any species. Although it is likely that some drugs may be conveniently delivered by this method, the use of gels and other novel drug delivery systems should be substantiated scientifically.
The AVMA Council on Biologic and Therapeutic Agents considered the message important enough to draft an AVMA position statement. Veterinarians have been seeking guidance from the AVMA and veterinary clinical pharmacologists about the efficacy and safety of such products, particularly drugs delivered in topically administered gels.
In November the Executive Board adopted the council's draft position. It states:
Compounding, including formulation in a novel drug delivery system (eg, transdermal), may impact the absorption and depletion of a drug. The use of a compounded drug may result in drug concentrations that lead to the development of an adverse drug event, including therapeutic failure. In order to minimize the risk of adverse events associated with compounded drugs, the following actions are recommended:
- The decision to use a compounded drug should be veterinarian (not pharmacy) driven, based on a valid veterinarian-client-patient relationship.
- Compounding must be implemented in compliance with the Animal Medicinal Drug Use Clarification Act (AMDUCA) and the FDA Compliance Policy Guide 608.400 titled Compounding of Drugs for Use in Animals. Use of compounded drugs in food animals is accompanied by food safety concerns that preclude their use unless information exists to assure avoidance of illegal tissue residues.
- Use of a compounded drug should be limited to:
- Those drugs for which both safety and efficacy have been demonstrated in the compounded form in the target species;
- Disease conditions for which response to therapy or drug concentration can be monitored; or
- Those individual patients for which no other method or route of drug delivery is practical.
- Use of a compounded drug should be accompanied by the same precautions followed when using a drug in its original form, including counseling of the client regarding potential adverse reactions and attention to the potential for unintended human or animal exposure to the drug.
Dr. Dawn M. Boothe of Texas A&M University, vice chair of the Council on Biologic and Therapeutic Agents and its pharmacology representative, said, "New compounding modalities being offered by many pharmacies have the potential for facilitating drug therapy in our patients. However, prescribing of a compounded drug ideally is based on scientific support.
"Prescribing of a compounded drug is associated with greater inherent risk than the uncompounded drug. It is the responsibility of the veterinarian, not the pharmacist, to assess the need and appropriateness of the compounded product and to ensure that all decisions and actions are done in the context of a valid veterinarian-client-patient relationship."