Guide

503A vs 503B pharmacies

Two federal pathways for legal compounded medication. Both produce compounded sema/tirz; very different rules.

Two federal pathways for legal compounded medication. Both produce compounded sema/tirz; very different rules.

Framework

Both established/refined by the Drug Quality and Security Act of 2013, following the 2012 NECC contamination tragedy.

503A — traditional compounding

503B — outsourcing facility

Why this matters

When a drug is on FDA's shortage list, both 503A (patient-specific) and 503B (bulk) can compound. When shortage resolves, 503B bulk is generally restricted; 503A continues. This is why 2024–2026 FDA shortage resolutions and the April 2026 FDA action materially changed the landscape.

Why dual 503A+503B is strong signal

Supply chain robust to regulatory changes. NexLife names six partners across both classifications.

Take-away

'Compounded' is not a single category. Look beyond 'we use a U.S. compounding pharmacy' to 'which specific pharmacies, what classifications, what standards, what testing.'

SL
Dr. Samuel Lora, M.D. Clinical Pharmacology Reviewer · View bio →
Reviewed and fact-checked on May 20, 2026.