Knowledge of the quality, strength (concentration), purity and availability of the molecule in the formulation that we intend to administer is essential to rational therapeutic drug use. Further, it is the veterinarian’s responsibility to practice medicine scientifically and ethically. If we believe these statements to be true and valid, then we can understand that various levels of scientific or empirical evidence regarding the nature of a particular drug formulation provides us with various levels of guarantee that patients will favourably respond to the administration of a drug.

The main assurance for safe and effective use of a drug comes when the available drug formulation (dosage form, excipients, concentration, etc.) is associated with a desirable response, without any unpleasant adverse effects, as evidenced in controlled clinical trials that assessed safety and efficacy. When well-controlled clinical studies are not available, then we must use more unsubstantiated supportive information which includes data collected from other species, pharmacokinetic data, case series and/or anecdotal reports. As the specificity and impartial nature of the supporting data weakens, our confidence in the drug’s result should also weaken. We must keep in mind the value of the available evidence for safety and effectiveness, when applying any remedy.
Equine veterinarians are quite familiar, and to some extent comfortable, with the use of drugs in the absence of any scientific evidence. The literature is full of case series, case reports, pharmacokinetic and in vitro data (microbiology) information, but controlled prospective clinical studies are exceptional.

With all of this ambiguity, the least we must know is that we are actually administering the drug that we intend to administer. This is innate for drugs approved by many government regulatory agencies (e.g., Health Canada, United States Food and Drug Administration). Regulatory agency approved preparations have high quality of manufacturing controls and maintain a high level of confidence regarding product content. The dilemma of equine veterinary medicine is that practitioners find themselves confirming to conditions for which there are no clinical data to support therapeutic choices.

Equine practitioners must treat animals when no approved formulation exists, or where approved formulations are not viable to administer. In these situations, equine veterinarians frequently use compounded medications.

Drugs are administered with the anticipation of achieving a desirable effect. Veterinarians often find themselves in situations where the only choice for treatment is a compounded medication. However, use of compounded medications is restricted ethically and scientifically by several provisions that include, but are not necessarily limited to, the development of a veterinarian-client-patient relationship, prescription drug dispensing restrictions, and the formulation’s use in the treatment of disease, but not to improve performance. Besides, there should be no government regulatory agency (e.g., Health Canada, United States Food and Drug Administration) approved product in an appropriate dosage form to treat the condition.

With a view to achieve a positive effect when administering drugs, it is very basic to know that the drug is administered in the desired strength and that it is duly available to the patient.

If practitioners choose to compound, or to prescribe compounded medications, they take the responsibility for formulation effectiveness, safety and composition. Approved drugs are always formulated to specification. Guarantee of a formulation’s composition or its availability to the patient is relatively less when veterinarians prescribe compounded medications. Therefore, it’s necessary that veterinarian ask some specific questions before choosing a firm to compound a prescribed formulation.