Prometrium Compounding Legal Status: FDA Approval, Label Details, and What Patients Need to Know

The direct answer

Prometrium (oral micronized progesterone, 100 mg and 200 mg capsules) has held FDA approval since 1998 for two indications only: secondary amenorrhea and prevention of endometrial hyperplasia during estrogen therapy. Compounding the same molecule at the same strength and route is legal only when a pharmacist compounds it under a patient-specific prescription and the prescriber documents why the FDA-approved product is not suitable for that particular patient, such as a peanut allergy to the approved capsule's excipient or a need for a dosage form Prometrium does not offer. A registered 503B outsourcing facility may compound without an individual prescription but must follow current Good Manufacturing Practice and report adverse events to the FDA; a traditional 503A pharmacy has no such reporting requirement. This distinction, not the chemical identity of the hormone, is what determines whether a given compounded progesterone product sits inside or outside the legal framework (see FDA's compounding laws and policies page: https://www.fda.gov/drugs/human-drug-compounding/compounding-laws-and-policies).

Disambiguating the names

"Progesterone," "micronized progesterone," "Prometrium," and "bioidentical progesterone" are often used loosely and interchangeably in patient-facing material, which causes confusion. Progesterone is the hormone itself. Micronized progesterone is a pharmaceutical processing step that increases absorption when taken orally. Prometrium is the brand name for the FDA-approved oral capsule containing micronized progesterone. "Bioidentical" describes the molecular structure being identical to the hormone the body produces; it is not an FDA regulatory category, and consumer-facing guidance has cautioned that the term has been used in ways that overstate the safety of unapproved products relative to approved ones. Compounded micronized progesterone, vaginal progesterone products such as Endometrin and Crinone, and injectable progesterone in oil are all different formulations of the same underlying molecule, not interchangeable products, and each has its own approval and evidence status.

FDA approval history

The FDA approved Prometrium under NDA 019781 in 1998, originally under Solvay Pharmaceuticals. Solvay was acquired by Abbott Laboratories in 2010, and the Prometrium NDA passed to AbbVie after Abbott's 2013 spinoff of its research-based pharmaceutical division. Editors should confirm current label ownership directly against the FDA's Drugs@FDA record before publication, since manufacturer assignments can change (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=019781). Generic oral micronized progesterone capsules have been available for over a decade, giving prescribers commercially manufactured alternatives to the branded product at the same approved strengths.

FDA approval of Prometrium relied significantly on data from the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial, which directly compared oral micronized progesterone with medroxyprogesterone acetate (MPA) in the context of conjugated equine estrogen therapy. Results showed that micronized progesterone maintained a greater portion of estrogen's beneficial HDL cholesterol effects compared to MPA while continuing to provide endometrial protection. Specific numerical findings from the PEPI trial are not cited here because prior citations could not be confirmed against original sources during this review; an editor with primary literature access should verify precise effect sizes before quoting specific values.

What the current label actually says

The Prometrium label specifies two approved dosing regimens: 200 mg daily for 12 days per 28-day cycle for endometrial protection during estrogen therapy, and 400 mg daily for 10 days for secondary amenorrhea. Individualized dosing decisions belong to the prescriber managing the patient's full history; this article does not provide dosing guidance for a specific person.

The label carries a boxed warning about cardiovascular disease and breast cancer risk, language that traces back to Women's Health Initiative (WHI) findings on combined estrogen-progestin therapy. The WHI trial that generated this warning used medroxyprogesterone acetate, not micronized progesterone, but the FDA applied the warning language across the progestin class, including Prometrium. This is a case where a class-wide regulatory action does not necessarily mean identical risk was demonstrated for every drug in the class, and readers should not assume the WHI risk estimates transfer exactly to micronized progesterone without their own supporting trial data.

Prometrium capsules contain peanut oil as an excipient, and the label contraindicates use in patients with a known peanut allergy. Not every generic manufacturer's capsule uses the same excipients, so a prescriber or pharmacist should check the specific product's inactive ingredients rather than assuming all micronized progesterone capsules are equivalent on this point.

The label does not cover vaginal, sublingual, topical, or rectal administration, and it does not carry an indication for luteal phase support in fertility treatment. Separate FDA-approved vaginal progesterone products (for example, vaginal inserts and gels marketed for luteal support) exist for that use and have their own labels; they are not the same product as Prometrium and are not addressed in detail here.

The legal framework for compounding

Two sections of the Federal Food, Drug, and Cosmetic Act govern compounded progesterone, and the distinction is the crux of the compounding question.

Section 503A covers traditional compounding pharmacies filling patient-specific prescriptions from a licensed prescriber. Under 503A, a compounded drug should not simply duplicate a commercially available FDA-approved product unless the prescriber documents a clinical reason the approved product will not work for that patient, such as an allergy to an inactive ingredient or a need for a strength or dosage form that is not commercially available. Because Prometrium is commercially available in 100 mg and 200 mg oral capsules, a 503A pharmacy compounding an identical oral capsule at those same strengths, without documented justification, sits outside the intended use of this exception.

Decision framework: is compounded progesterone the right path for this patient?

This content is not intended to serve as medical advice for any individual reader; rather, it offers a framework through which patients and their prescribers may jointly evaluate Prometrium's role in their treatment approach.

Step 1: Is there a documented reason the FDA-approved product cannot be used?

• Peanut allergy and the specific approved or generic product contains peanut oil: this is a recognized 503A justification.
• Need for a route Prometrium does not offer (vaginal, sublingual, topical) for a use where no FDA-approved product exists: potentially justifiable, but check whether an FDA-approved vaginal progesterone product already covers the intended use before compounding.
• Preference for compounded product based on marketing claims of being "more natural" or "safer": not a documented clinical justification. A 2020 National Academies of Sciences, Engineering, and Medicine consensus report concluded there was insufficient evidence that compounded bioidentical hormones are safer or more effective than FDA-approved hormone therapies; verify the exact report title and findings directly before citing a specific quote.

Step 2: If compounding is justified, which type of facility?

• A 503A pharmacy compounds against an individual prescription, is regulated primarily by the state pharmacy board, and has no mandatory FDA adverse event reporting requirement.
• A 503B outsourcing facility is FDA-registered, must follow current Good Manufacturing Practice, can supply without an individual prescription, and must report adverse events to the FDA. When a documented clinical need supports compounding, a 503B facility carries more third-party oversight than a 503A pharmacy.

Step 3: What should be documented in the chart regardless of path chosen?

• The specific reason the FDA-approved product was not used.
• The compounding facility's registration status (503A vs 503B).
• A plan for monitoring the patient, since a compounded product will not carry the FDA-required boxed warning or medication guide that comes with Prometrium, and any cardiovascular or breast cancer risk counseling needs to happen independently of the product labeling.

Step 4: When to escalate to the prescriber or seek urgent care.

• New or worsening chest pain, shortness of breath, leg swelling or pain, sudden severe headache, vision changes, or signs of an allergic reaction after starting any progesterone product (compounded or approved) warrant urgent evaluation, not a wait-and-see approach.
• Unexplained vaginal bleeding on any progesterone or hormone regimen should be reported to the prescriber promptly rather than attributed automatically to the medication.

Exceptions and gray zones. A documented allergy or intolerance to an approved product's inactive ingredients is the clearest justification for 503A compounding. A stated preference for a compounded product because it is marketed as "bioidentical" or "natural," without an allergy or formulation gap, does not meet the 503A clinical-difference standard as commonly interpreted by regulators, and prescribers directing patients toward compounding on that basis alone should reconsider the rationale.

What the professional societies say, in general terms

Multiple professional organizations, including the American College of Obstetricians and Gynecologists, the North American Menopause Society, and the Endocrine Society, have published statements recommending that FDA-approved hormone products be used preferentially over compounded bioidentical hormones, reserving compounding for patients who cannot tolerate or use an approved product. Earlier drafts of this article included specific verbatim quotations attributed to these organizations; those quotations could not be verified against a retrievable primary source in this review pass and have been removed rather than reproduced inexactly. An editor with access to the original committee opinions and position statements should confirm exact wording before any direct quotation is restored.

State-level variability

Federal law under 503A and 503B sets a floor. State pharmacy boards can add licensing and inspection requirements on top of that floor, and some states have addressed "bioidentical hormone" marketing claims specifically. Requirements vary by state and change over time, so a prescriber or patient should verify current rules with the relevant state board of pharmacy rather than relying on a general description here. The FDA has periodically taken enforcement action against compounding pharmacies, including some hormone-related cases, but a specific count of warning letters over a given period could not be verified in this review pass and has been removed rather than stated as an unverified number.

Safety surveillance gap

FDA-approved drugs like Prometrium are covered by mandatory manufacturer adverse event reporting to the FDA. Section 503A compounding pharmacies have no equivalent mandatory reporting obligation; only 503B outsourcing facilities must report adverse events. The FDA's Sentinel System is a large post-market safety surveillance program built on electronic health data (https://www.fda.gov/safety/fdas-sentinel-initiative), but it is designed around identifiable, coded drug products and is not structured to reliably distinguish a compounded progesterone fill from a manufactured one. This means the long-term safety data available for Prometrium and its generics, built up over more than two decades of post-market monitoring, does not have a direct equivalent for compounded progesterone formulations. That gap is a real limitation in what can be known about compounded product safety, not evidence that compounded products are unsafe.

Evidence boundary: what is established, what is not

Established: Prometrium is FDA-approved for two specific indications. Compounding of micronized progesterone under 503A requires a patient-specific prescription and, when a commercially available equivalent exists, a documented clinical reason. 503B facilities operate under cGMP and must report adverse events; 503A pharmacies do not have that same reporting requirement. Compounded progesterone products have not undergone FDA review for safety, effectiveness, or quality before marketing.

Plausible but requiring direct verification before being stated precisely: The magnitude of HDL-cholesterol benefit reported in the original micronized-progesterone-versus-MPA comparison trial; the exact breast cancer hazard ratio historically associated with WHI's estrogen-plus-progestin arm; the exact wording of professional society statements on compounded hormones; state-specific licensing requirements as currently written.

Not established: That compounded micronized progesterone is safer, more effective, or better tolerated than FDA-approved Prometrium or its generics. That the WHI risk findings, generated with medroxyprogesterone acetate, transfer at an identical magnitude to micronized progesterone. That potency or contamination failure rates for compounded progesterone differ from FDA-approved products by any specific measured amount; no page-level source here supports a numeric failure rate in either direction.

When to talk to a prescriber rather than decide alone

Questions about switching between an FDA-approved and a compounded progesterone product, about whether a peanut allergy or other intolerance justifies compounding, or about unexpected bleeding or cardiovascular symptoms while on any progesterone product belong with the prescribing clinician, not with general reference material. This article describes the regulatory landscape; it does not recommend a specific product, dose, or route for any individual reader.