Practitioner Updates

Pharmacist’s Corner: 503a vs. 503b Pharmacies


Compounded medications are often necessary to effectively treat our patients, but there are frequently news headlines reminding us that compounded medications can pose a risk with regard to quality. However, selecting a high-quality compounding pharmacy can decrease the risk of receiving a low-quality product. One way to evaluate quality is whether the compound is coming from 503a or 503b pharmacies.

The biggest difference between these two types of pharmacies is that 503a pharmacies compound medications in accordance with United States Pharmacopeia (USP) Standards and are regulated by the states, while 503b pharmacies compound medication in accordance with Good Manufacturing Practices (cGMP) and are regulated by the Food and Drug Administration.

If you can get a product from a 503b compounding facility versus a 503a one, then you know you are getting a medication that:

  • has been proven to contain the correct amount of active drug
  • is stable until its “beyond use” date
  • is sterile (if it’s a sterile product)

This guarantee is due to the stringent testing required by cGMP for all products.

While preparing compounds in line with manufacturing standards produces a higher quality product due to all the additional testing required, these 503b facilities are limited in that they aren’t able to make anything in small quantities.

If you need a product designed to meet the needs of a specific patient, such as a particular flavor or a unique suspension, then a 503a pharmacy will be better able to meet your needs.

Despite their differences, both types of compounding pharmacies have a place in veterinary medicine. 503a pharmacies are the traditional compounding pharmacies that make patient-specific medications in small quantities. However, oftentimes the veterinary profession has a need for a compounded product (aka not FDA-approved) in quantities more similar to manufactured products. 503b pharmacies are essentially manufacturing compounded products.

By Lauren Forsythe,
Medication Dispensary Coordinator