In its article on Drug Shortages, the American Veterinary Association Makes this statement and reminder regarding compounded drugs:

• Is it necessary to have the drug compounded? Recognize that AVMA agrees that compounds might be necessary in some situations (nonfood animals), however also know that unlike drugs that are approved by the FDA, potency, stability, safety and efficacy of compounds are often not documented and may be unknown. Recall that price alone is not a reason for using a compounded product. TheAVMA’s Compounding page is a great resource, as is a webinar featuring a board-certified pharmacologist that AVMA held earlier this year (AVMA member login required).
• quoted from here