503A or 503B—Knowing When to Order from Each One

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Where do you get your compounded medications from? Before the introduction of 503B outsourcing facilities in 2013, this was probably a pretty straightforward question. Now, there are more sources than ever to turn to for your veterinary patients’ compounded drugs. The increased options add complexity to both patient and bulk in-house clinic orders. But, arming yourself with knowledge about the differences between 503A compounding pharmacies and 503B outsourcing facilities, and the questions to consider when deciding where to order, can demystify this choice.

Understanding the specifics behind the products you receive from 503As and 503Bs will give you the confidence that you’re providing your patients with the highest standard of care. 

What is the difference between 503A and 503B?

503A compounding pharmacies and 503B outsourcing facilities may be of the same species but are not of the same breed. Familiarity with the differences between the two can help you make an informed decision on which type of compounder will best meet your needs and the needs of your patients, ensuring your patients receive the highest quality of care.  Let’s review the basics.

503A Compounding Pharmacies

503A compounders are the traditional, neighborhood compounding pharmacies that are familiar to most veterinarians. 503A compounding pharmacies:

  • Are regulated primarily by the State Board of Pharmacy (SBOP).
  • Must comply with United States Pharmacopeia (USP) standards for compounding nonsterile and sterile medications (USP 795 and USP 797) and SBOP regulations.
  • Are limited to dispensing medications for home use only when a patient-specific prescription is available; the customized formulations are produced to meet the needs of an individual patient.
503B Outsourcing Facilities

503B manufacturers and outsourcing facilities, in contrast, are newer, coming into existence in 2013 with the implementation of the Drug Quality and Security Act, which added Section 503B to the federal Food, Drug, and Cosmetic Act. 503B outsourcing facilities:

  • Are regulated by the Food and Drug Administration (FDA).
  • Must comply with the FDA’s current Good Manufacturing Practice (cGMP) standards (21 CFR Parts 210 and 211) in addition to USP 795, USP 797, and SBOP regulations.
  • Can dispense large quantities of traditionally compounded veterinary medications for office use with or without a prescription; the customized drug therapies produced can address both patient and practice needs.

What Is cGMP Compliance and Why Does It Matter?

While both traditional 503A compounding pharmacies and 503B outsourcing facilities have quality and safety requirements they are obligated to meet, 503B outsourcing facilities are held to more rigorous standards—the same standards as human pharmaceutical manufacturers. Compliance with cGMP standards means that 503B outsourcing facilities must:

  • Follow Good Documentation Practices (GDPs) which ensure traceability and tracking throughout each step of the manufacturing process from receipt of raw materials to finished product testing. If quality or safety issues arise, they can be found and addressed quickly before medication is released for patient use.
  • Conduct finished product testing on every batch of medication they manufacture for potency, along with sterility and endotoxins, when applicable. You can have confidence that the medications your practice and patients receive are safe and will meet label claims.
  • Perform stability testing using validated methods to assign expiration dates and confirm the medications will maintain their integrity throughout that timeframe. These tests include long-term and accelerated testing, stress testing, and container closure system studies. In contrast, 503A compounders often rely on clinical literature, drug manufacturer recommendations, and USP limits to assign a beyond-use date that typically is substantially shorter.
  • Assess air and surface microbial levels in primary compounding areas for every batch. This regular environmental monitoring (EM) prevents microbial contamination from occurring—ensuring the medication you’re getting is safe. 503A compounding pharmacies are not required to conduct continuous EM, so problems with sterility may not be detected quickly.        

503A or 503BQuestions to Ask Before You Order

There are many important differences between 503A compounding pharmacies and 503B outsourcing facilities, but both have their place in supporting effective veterinary healthcare. Let’s take a look at some questions that will help you decide which type of supplier best meets your patients’ and your practice’s needs.

When to Order From a 503A

Am I ordering a compounded medication that is used only by a small number of patients?

503A compounding pharmacies specialize in preparing customized drugs for individual patients, so if you only have one or a few patients who need a particular medication, ordering from a 503A pharmacy could meet your needs. Plus, with a 503A compounding pharmacy like Stokes, if a medication you order has a 503B equivalent through its sister company, Epicur, that’s what you’re going to get—so, in some cases, you’ll get all the benefits of 503B quality and safety standards even when you’re just filling an individual prescription.     

Do I need a fast turnaround time on a compounded drug that’s currently unavailable through a 503B outsourcing facility?

Because 503B outsourcing facilities have to validate all of their processes and testing methods and must conduct stability testing on numerous batches of a new medication or formulation before offering a new product, they typically have a set list of offerings. Adding a new drug to the portfolio takes a significant amount of time in development. However, if the drug you need is part of the 503Bs set list of offerings it’s likely already on the shelf stocked and ready to ship. In these cases, 503B lead times for getting an order out the door are much quicker than a compounding pharmacy. Most compounded prescriptions from a 503A are made to order and must be compounded at that time.

When you need a compounded medication that isn’t currently offered from a 503B outsourcing facility, ordering from a 503A compounding pharmacy is your next best option.   

Do I have a patient that requires a unique dose not offered by a 503B outsourcing facility?

This can be a complex question to answer. If you are working with a patient who needs, say, 2.4 mg of a particular medication, and 503B outsourcing facilities only offer 2 mg or 3 mg, it may make sense to order from a 503A compounding pharmacy but remember that thorough potency testing may not have been done. The drawbacks that come with a lack of testing to confirm that a particular batch actually contains the requested dosage need to be considered along with the advantages of being able to order a customized dosage. 

The Drawbacks & Risks of Untested Products

Commercially manufactured drugs are held to +/-10%, which is the acceptable range for potency. So, if you’re ordering a 2.125 mg that’s actually within 10% it makes sense just to order the manufactured product.

If you order the 2.125 mg from a compounding pharmacy the drug you’re getting could likely be well outside of that 10% window (remember, they do not have to test!). Many studies on compounding pharmacy preparations have shown a wide range of potency percentages, from over potent to not potent enough. This is why it’s important to weight the pros and cons of where you order medications from.

When to Order From a 503B

Is the compounded drug I need available from a 503B outsourcing facility?

Because 503B outsourcing facilities are overseen by the FDA and have to operate in compliance with the FDA’s cGMP requirements just like major pharmaceutical companies, the drugs they manufacture meet the highest quality standards. The types of medications available from 503B outsourcing facilities are extensive and come in many formats including tablets, oral liquids, injectables, and ophthalmics. If the compounded medication you need is available for order from a 503B outsourcing facility, you can have confidence in the quality and safety of the medications your patients are receiving.    

Do I want to order a larger quantity of a compounded medication to keep in stock for office use?

503B outsourcing facilities are like “super compounders”—they manufacture large quantities of traditionally compounded medications that your veterinary practice can then keep on hand, so your patients will receive the treatment they need when they need it. The larger batch sizes result in cost savings compared with filling individual prescriptions through a 503A compounding pharmacy. Plus, the extensive stability testing conducted by 503B outsourcing facilities allows longer expiration dates to be assigned to their products, simplifying inventory management and decreasing the likelihood of patients taking unsafe, expired medication.      

Am I prescribing a drug whose effectiveness is highly dependent upon accurate dosing?

For chemotherapy drugs and other treatments where the appropriate dosage window is quite small, ordering from a 503B outsourcing facility becomes incredibly important. With these types of drugs, if the potency is 10-15% lower than what was prescribed, you’re underdosing the patient and drug resistance can result. If the potency is 15-20% too high, the patient could experience toxicity or side effects. The extensive testing 503B outsourcing facilities must perform in areas including potency, sterility, endotoxin levels, and stability enables you to trust the medication you’ve prescribed and have confidence that your patients are receiving the best care possible.     

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