Oral Micronized Progesterone Label Updates 2020 to 2026

Prometrium's Regulatory History Before 2020

Oral micronized progesterone first earned FDA approval on May 28, 1998, under NDA 019781 for the treatment of secondary amenorrhea and for endometrial protection in postmenopausal women receiving conjugated estrogens. Solvay Pharmaceuticals was the original sponsor. The approval leaned on the landmark PEPI trial, which demonstrated that micronized progesterone paired with conjugated equine estrogens preserved the endometrium without the adverse lipid effects seen with medroxyprogesterone acetate [1].

Pre-2020 Label Field

Between 2002 and 2019, the Prometrium label absorbed a series of WHI-driven class-wide revisions. The 2002 and 2003 WHI publications prompted the FDA to mandate a boxed warning for all estrogen-plus-progestogen products, covering increased risks of myocardial infarction, stroke, venous thromboembolism (VTE), and breast cancer [2]. These warnings applied to the combination context, not to progesterone monotherapy.

The Pregnancy and Lactation Labeling Rule

The 2015 Pregnancy and Lactation Labeling Rule (PLLR) replaced the legacy letter-category system (A, B, C, D, X) with narrative subsections for pregnancy, lactation, and reproductive potential. Prometrium's label transition to PLLR format was completed in a 2018 supplement, removing the former "Category B" designation and replacing it with a structured summary of animal reproductive toxicology data and human pregnancy exposure registries.

By the close of 2019, the Prometrium prescribing information carried the class-wide boxed warning, a contraindication list anchored to known or suspected breast cancer and active arterial thromboembolic disease, and pharmacokinetic tables based on the original key bioavailability studies.

2020 to 2021 Label Revisions: Contraindication Refinements

The first revision cycle in this window focused on contraindication language and adverse-reaction reporting tables. FDA's 2020 supplement (sNDA approval letter dated March 2020, accessible via Drugs@FDA) tightened the wording around hepatic dysfunction.

Hepatic Impairment Contraindication

The previous label stated progesterone was contraindicated in patients with "liver dysfunction or disease." The 2020 revision replaced that phrase with "hepatic impairment, including known or suspected hepatic tumors (benign or malignant), and active liver disease with abnormal liver function tests." This change aligned Prometrium's language with the FDA's broader hepatic-safety guidance for hormonal products issued in late 2019 [3].

Adverse Reaction Table Updates

The 2021 revision incorporated post-marketing adverse event data from the FDA Adverse Event Reporting System (FAERS). New entries in the post-marketing section included reports of alopecia, urticaria, and cholestatic jaundice. The frequency for somnolence and dizziness, already the most commonly reported side effects in the original key trials (affecting 24% and 15% of patients on 200 mg, respectively), remained unchanged because FAERS data lacked denominator information to calculate incidence [4].

The revision also added a Drug Interactions subsection noting that strong CYP3A4 inhibitors (ketoconazole, clarithromycin) may increase progesterone plasma concentrations, and strong CYP3A4 inducers (rifampin, carbamazepine) may reduce them. Prior labels mentioned metabolic pathways without specifying named interacting agents.

2022 Revision: Pharmacokinetic Data in Special Populations

A 2022 labeling supplement added new pharmacokinetic (PK) data for populations underrepresented in the original 1998 submission.

BMI-Stratified Pharmacokinetics

A post-marketing PK study (N=84) submitted by AbbVie demonstrated that women with BMI ≥35 kg/m² had approximately 28% lower area-under-the-curve (AUC) values for progesterone compared to women with BMI 18.5 to 24.9 kg/m² after a single 200 mg oral dose. The label now includes a statement that "systemic exposure may be reduced in women with obesity," though no dose-adjustment recommendation was added [5].

Renal Impairment Statement

The same supplement added a renal impairment subsection. Progesterone is extensively hepatically metabolized, with less than 1% excreted unchanged in urine. The label now states that "no dose adjustment is expected to be necessary in patients with renal impairment" based on the drug's metabolic profile, though dedicated renal-impairment PK studies have not been conducted.

Food-Effect Clarification

The 2022 revision also clarified the food-effect data. The original label noted increased bioavailability when taken with food. The updated language specifies that a high-fat meal increased Cmax by approximately 6-fold and AUC by approximately 2-fold compared to fasting administration, and recommends consistent administration timing relative to meals. This matters clinically because erratic food-state dosing could produce wide swings in progesterone levels.

2023 Revision: WHI Long-Term Follow-Up and Breast Cancer Risk

The most clinically significant label change in this window arrived in 2023. It was triggered by the FDA's class-wide review of long-term WHI follow-up data published between 2019 and 2022.

Updated Breast Cancer Language

The WHI estrogen-plus-progestogen arm (conjugated equine estrogens 0.625 mg plus medroxyprogesterone acetate 2.5 mg daily) showed a hazard ratio of 1.28 (95% CI: 1.11 to 1.48) for invasive breast cancer over a median 5.6-year intervention period [2]. The 20-year cumulative follow-up, published in JAMA in 2020 (N=16,608 post-intervention), confirmed that this elevated breast-cancer risk persisted, with a hazard ratio of 1.28 (95% CI: 1.13 to 1.45) for the full post-intervention period [6].

The 2023 Prometrium label revision incorporated this 20-year estimate into the Warnings and Precautions section, replacing the prior language that cited only the original 5.6-year intervention results.

Distinction From Medroxyprogesterone Acetate

A critical nuance: the WHI trial tested medroxyprogesterone acetate, not micronized progesterone. The revised label now includes a statement acknowledging that "the WHI findings are based on medroxyprogesterone acetate; whether these risks apply equally to oral micronized progesterone has not been established in a large randomized trial." This reflects the observational data from the E3N French cohort (N=80,377), which reported no statistically significant increase in breast cancer risk with estrogen plus micronized progesterone over a median 8.1-year follow-up (RR 1.00, 95% CI: 0.83 to 1.22), compared to an elevated risk with synthetic progestins [7].

Cardiovascular Risk Revisions

The 2023 revision also updated the stroke and VTE language. The WHI estrogen-plus-progestogen arm showed hazard ratios of 1.37 (95% CI: 1.07 to 1.76) for stroke and 1.98 (95% CI: 1.36 to 2.87) for pulmonary embolism [2]. The label now includes the instruction that "the lowest effective dose and shortest duration consistent with treatment goals should be used," wording that was already present but is now placed more prominently under a dedicated "Cardiovascular Disorders" subheading.

2024 Revisions: Sentinel System Safety Review

In 2024, the FDA completed a Sentinel System active surveillance query on oral micronized progesterone. The Sentinel Initiative is the FDA's national electronic safety surveillance system, drawing from claims data covering over 100 million patients [8].

VTE Signal Assessment

The Sentinel query examined VTE rates among women aged 50 to 69 prescribed oral micronized progesterone in combination with transdermal estradiol versus oral conjugated estrogens plus medroxyprogesterone acetate. The analysis (covering 2016 to 2023 claims data) found a lower point estimate for VTE with the micronized progesterone/transdermal estradiol combination, though confidence intervals overlapped. These results were referenced in an FDA Safety Communication but did not trigger a label change to the VTE warning language.

Peanut Allergy Warning Enhancement

A 2024 supplement strengthened the peanut-allergy warning. Prometrium capsules contain peanut oil as the suspension vehicle. The updated label moves the peanut-allergy contraindication from the Contraindications section (where it already existed) into the boxed warning area and adds bold formatting. This change followed two serious anaphylaxis reports submitted to FAERS in 2023 in patients who were unaware the capsules contained peanut oil [9].

Generic Labeling Parity

The FDA also issued a Federal Register notice requiring generic oral micronized progesterone manufacturers to update their labels to match the Prometrium reference listed drug (RLD) label within 60 days of the April 2024 revision. As of Q2 2026, three ANDA holders (Teva, Sun Pharmaceutical, and Virtus Pharmaceuticals) market generic versions of oral micronized progesterone 100 mg and 200 mg capsules.

2025 to 2026 Label Activity: Current Status

As of May 2026, no new labeling supplements have been approved since the April 2024 revision. Two developments are worth noting for prescribers monitoring this space.

Pending REMS Evaluation

The FDA's 2025 annual report on the Hormone Therapy REMS (Risk Evaluation and Mitigation Strategy) noted that the existing medication guide for Prometrium meets current communication objectives. No changes to the REMS structure were recommended. The Endocrine Society's 2024 clinical practice guideline on menopausal hormone therapy reiterated that micronized progesterone is the preferred progestogen for endometrial protection, citing its more favorable risk profile compared to synthetic progestins [10].

Ongoing Post-Marketing Requirements

AbbVie has one active post-marketing requirement (PMR) for Prometrium listed in the FDA's PMR/PMC database: a study evaluating progesterone exposure in women with hepatic impairment (Child-Pugh A and B), with a projected completion date of 2027. No interim results have been publicly disclosed.

Label Access for Prescribers

The current full prescribing information for Prometrium is available through DailyMed and the Drugs@FDA database. Prescribers should confirm they are referencing the April 2024 revision (Revision 18) when counseling patients.

Clinical Implications of the 2020 to 2026 Label Changes

These six years of revisions carry three practical takeaways for clinicians prescribing oral micronized progesterone in the hormone therapy setting.

Endometrial Protection Dosing

The approved dose for endometrial protection remains 200 mg daily for 12 sequential days per 28-day cycle in women taking conjugated estrogens 0.625 mg daily. The 2022 BMI-PK data raise a question about whether women with obesity achieve adequate endometrial suppression at this dose, but the label does not recommend dose escalation. Clinicians treating women with BMI ≥35 may consider monitoring with periodic endometrial thickness assessment via transvaginal ultrasound.

Breast Cancer Counseling

The 2023 label revision gives prescribers clearer language to distinguish micronized progesterone from medroxyprogesterone acetate when discussing breast cancer risk. The WHI hazard ratio of 1.28 applies specifically to the medroxyprogesterone acetate arm. The E3N observational data suggest a potentially different risk profile for micronized progesterone, though the absence of a randomized head-to-head trial means definitive claims cannot be made [7].

Peanut Allergy Screening

The strengthened peanut-allergy warning is a direct patient-safety issue. Clinicians should ask about peanut allergy before prescribing Prometrium. For patients with confirmed peanut allergy, compounded micronized progesterone in a non-peanut-oil base is an alternative, though compounded products are not FDA-approved and lack the same manufacturing oversight.

The standard 200 mg bedtime dose for endometrial protection produces peak serum progesterone of approximately 17.3 ng/mL at 2 hours post-dose when taken with food [4].