Illustration by Wendy Brooks, DVM.
Sometimes the medication that your pet needs was designed for people and does not come in a form convienient for a cat or dog. Sometimes the bitter taste causes pets to spit it out. A compounding pharmacy has the ability to reformulate the medication, in a batch just the size you need, so that your pet may actually be willing to take it! If your veterinarian needs a compounding pharmacy to make a flavored oral liquid or conveniently sized capsule, a compounding pharmacy may be able to do it for you.
You will need a prescription from your veterinarian to use a compounding agency, just as you would if your pet needed a prescription filled from a drug store.
There are benefits and risks to using a compounding pharmacy. A compounder buys ingredients in bulk, and mixes up what you need. The key here is to use a reputable, good compounder. Some compounding pharmacies make regular mistakes and the result could be disastrous. Your veterinarian will know which ones are reliable.
Some of the benefits are that one gives you access to medication that is no longer manufactured and thus unavailable elsewhere. Hypo-allergenic medications can be made. The taste can be altered so that your pet can have a pill that tastes like tuna, chicken, or some other flavor. Small versions of small pills can be made. Some pills can be made to dissolve on your pet's tongue, thus making it nearly impossible for the pill to be spit out. You can sometimes choose between liquid, capsule or pill.
The downside is a much higher risk of contamination, as sterility is a concern with compounding pharmacies, and many have had to recall all sterile medications. Contamination can harm your pet, sometimes seriously or even fatally. That's why you need to work with a reputable compounder.