Compounding Resource

503A and 503B serve different compounding needs.

Both pathways support compounded medications, but they differ in how an order begins, who receives the medication, and which federal requirements apply.

Compare the two pathways

The practical distinction

A

503A

An identified patient and prescription

The process generally begins with a licensed provider prescribing for an individual patient.

B

503B

An approved buyer and facility need

The process may begin with a pharmacy, clinic, hospital, or facility seeking qualified outsourcing support.

Side-by-Side Comparison

The differences that matter most

Use this comparison as a practical starting point. The correct pathway can also depend on the medication, intended use, state law, and the receiving organization.

Comparison of section 503A patient-specific compounding and section 503B outsourcing facilities
Compare	503A compounding	503B outsourcing
Primary model	Patient-specific compounding by a licensed pharmacist in a state-licensed pharmacy or federal facility, or by a licensed physician.	Compounding within an FDA-registered outsourcing facility under the direct supervision of a licensed pharmacist.
Prescription basis	Compounding is based on a valid prescription for an identified individual patient. Limited anticipatory compounding may occur under applicable requirements.	An outsourcing facility may compound with or without prescriptions for identified individual patients.
Common fit	Customized strengths, dosage forms, ingredients, or other provider-directed treatment needs for an individual patient.	Facility-oriented supply needs, including recurring sterile purchasing and non-patient-specific office stock where permitted.
Who it commonly serves	Individual patients through their licensed prescribers and the pharmacy dispensing the patient-specific prescription.	Hospitals, clinics, surgery centers, pharmacies, and other permitted healthcare-facility buyers.
Sterile and nonsterile scope	May include sterile or nonsterile compounding depending on pharmacy capabilities, licensure, and applicable standards.	An outsourcing facility is defined as being engaged in sterile drug compounding and may also compound nonsterile drugs.
Registration and oversight	Not registered with FDA as an outsourcing facility. State boards of pharmacy generally provide primary day-to-day oversight, while FDA retains applicable authority.	Registered with FDA as an outsourcing facility and inspected by FDA according to a risk-based schedule.
Quality framework	When all conditions of section 503A are met, compounded drugs are exempt from federal CGMP requirements. Applicable state law and pharmacy-practice standards still apply.	Subject to federal CGMP requirements, along with product reporting, adverse-event reporting, labeling, and other section 503B conditions.
FDA approval status	Compounded drugs are not FDA-approved and do not undergo FDA premarket review for safety, effectiveness, or quality.	Compounded drugs are not FDA-approved. Registration as an outsourcing facility does not itself mean that a facility or product has been approved by FDA.

This comparison is a general overview and is not an exhaustive statement of federal or state requirements.

Choose Your Path

Start with the need, not the acronym

Select the pathway that best reflects how the medication will be prescribed, purchased, and used.

Still unsure? Contact our team

503A Provider Pathway

Patient-specific prescribing support

Begin here when a licensed provider is prescribing a compounded medication for an identified individual patient.

Explore 503A services

503B Buyer Pathway

Facility and recurring supply support

Begin here when a permitted healthcare buyer needs outsourcing, qualification, documentation, or recurring sterile supply support.

Explore 503B services