What FDA Approval Means: Rigorous Standards, Off-Label Use & Compound Safety

Under the U.S. Federal Food, Drug, and Cosmetic Act (FD&C Act), the Food and Drug Administration (FDA) evaluates pharmaceuticals through its Center for Drug Evaluation and Research (CDER) [1].

To secure marketing approval, a drug sponsor must demonstrate two legal standards:

• Safety: The drug's documented health benefits outweigh its known and potential risks for the intended patient population.
• Substantial Evidence of Effectiveness: Proven through at least two adequate and well-controlled Phase 3 randomized trials showing that the drug accomplishes its claimed clinical effect [1].

A critical point of confusion in peptide communities is understanding what the FDA actually approves. US law requires new drugs to be tested before approval to show a well-defined benefit that is commensurate with their risks, and the laws, standards, and special approval pathways governing that process have changed substantially since the 1980s [2].

The FDA does not approve a chemical substance in the abstract (e.g., 'the molecule semaglutide'). Rather, the FDA approves a specific drug product manufactured by an audited company under strict cGMP protocols, formulated with specific excipients, packaged in a validated delivery device (e.g., Wegovy pen), and labeled for a specific medical indication. Bulk semaglutide powder sold for 'research use' is not an 'FDA-approved' product.

Once the FDA approves a drug for one indication, licensed physicians in the United States have the legal authority to prescribe it 'off-label' for other unapproved medical conditions if they judge it clinically appropriate based on scientific literature [3].

However, the pharmaceutical manufacturer is legally prohibited from marketing, advertising, or promoting the drug for off-label uses. Off-label prescribing must be distinguished from using completely unapproved, non-FDA-cleared experimental compounds (such as BPC-157 or TB-500), which have no approved medical use in the United States [3].

Pharmacy compounding is a traditional practice intended to tailor custom medicines for individual patients who cannot use commercial drugs (e.g., patients with severe dye allergies or requiring liquid pediatric formulations) [4].

Compounded drugs are governed by Section 503A (state-licensed community compounding) and Section 503B (registered outsourcing facilities) of the FD&C Act. Compounded drugs are not reviewed or approved by the FDA for safety or efficacy. The FDA has repeatedly issued safety alerts warning patients that unverified compounded peptides can contain salt forms (such as semaglutide sodium), improper concentrations, and bacterial endotoxins [4].

FDA oversight does not end upon drug approval. Among 222 novel therapeutics approved by the FDA from 2001 through 2010, 32% were affected by a postmarket safety event (a withdrawal, a new boxed warning, or an FDA safety communication) during a median follow-up of 11.7 years [5]. CDER continuously monitors post-marketing safety through:

• MedWatch: The FDA Adverse Event Reporting System (FAERS), capturing voluntary and mandatory post-approval toxicity reports.
• Risk Evaluation and Mitigation Strategies (REMS): Specialized safety programs that mandate prescriber certification or patient registries for medications with serious risks.
• Label Updates & Boxed Warnings: Mandating updated safety information or withdrawing drugs if unexpected post-marketing risks outweigh therapeutic benefits.