Prometrium Pre-Surgery Hold Window: What Clinicians and Patients Need to Know

What does the Prometrium label say about surgery?

The instruction is one sentence in the cardiovascular warnings of the current label (Revision 02/2026): 'If feasible, discontinue PROMETRIUM at least 4 to 6 weeks before surgery of the type associated with an increased risk of thromboembolism, or during periods of prolonged immobilization' [1]. The same section says to discontinue immediately if a PE, DVT, stroke or MI occurs or is suspected [1].

Two details matter for anyone applying that sentence. The instruction is conditional ('if feasible'), and it is tied to clot-risk surgery and prolonged immobilization rather than to any operation [1]. Prometrium's labeled uses are prevention of endometrial hyperplasia in postmenopausal women with a uterus who are taking conjugated estrogens tablets, and secondary amenorrhea; the hyperplasia regimen is 200 mg at bedtime for 12 days of each 28-day cycle [2].

What clot-risk evidence does the label discuss?

The warnings section that carries the hold instruction summarises the Women's Health Initiative estrogen-plus-progestin trial: 16,608 postmenopausal women aged 50 to 79 (average 63.4), conjugated estrogens 0.625 mg plus medroxyprogesterone acetate 2.5 mg daily for 5.6 years, with relative risks versus placebo of 1.87 for DVT (95% CI 1.37 to 2.54) and 1.98 for PE (95% CI 1.36 to 2.87) [2]. The progestin in that trial was medroxyprogesterone acetate, not micronized progesterone [5]. The label does not say that the trial determined the 4-to-6-week timing.

The label also limits how far those numbers travel: only daily oral conjugated estrogens 0.625 mg and medroxyprogesterone acetate 2.5 mg were studied, so the relevance of the WHI findings to lower doses, other routes of administration, or other estrogen-plus-progestogen products is not known [2]. Prometrium is one of the menopausal hormone products whose updated labeling FDA approved on 2026-02-12; the boxed warning language on cardiovascular disease, breast cancer and probable dementia was removed, while the WHI data remain in the Warnings and Clinical Studies sections [3][6][1].

What is known about progesterone and clotting markers?

One randomized trial measured hemostatic variables in 45 healthy postmenopausal women aged 45 to 64, assigned to cyclic oral estradiol plus progesterone, transdermal estradiol plus progesterone, or no hormonal treatment, with assays at baseline and after six months [4]. Oral, but not transdermal, estradiol combined with progesterone significantly increased prothrombin activation peptide (F1+2) and decreased antithrombin activity compared with no hormonal treatment [4]. There were no significant changes in fibrinogen, factor VII, von Willebrand factor, protein C, fibrin D-dimer or plasminogen between or within the three groups [4].

Both active arms included progesterone, so that trial does not separate progesterone's own contribution from the estrogen it was paired with; what it shows is that the route of estradiol moved the markers [4]. It also used estradiol, whereas the Prometrium label's dosing and studies are with conjugated estrogens [2].

Which patients should not be taking it at all?

The label lists six contraindications: hypersensitivity to the ingredients (the capsules contain peanut oil, so peanut allergy is one); abnormal genital bleeding of unknown cause; known, suspected or past breast cancer; active DVT or PE, or a history of either; active arterial thromboembolic disease such as stroke or MI, or a history of these; and known liver dysfunction or disease [2]. For a woman with a prior clot, the label's position is that the drug is contraindicated, which is a different statement from a 4-to-6-week hold [2].

Two more label points are relevant before surgery. Progesterone may cause some degree of fluid retention, and the label says women with cardiac or renal dysfunction warrant careful observation [2]. Pharmacokinetics have not been studied in hepatic or renal impairment [1].

What about anesthesia and other drugs?

The label describes the drug's own central effects: it 'may cause transient dizziness and drowsiness and should be used with caution when driving a motor vehicle or operating machinery', it should be taken as a single daily dose at bedtime, and during initial therapy a few women experienced extreme dizziness or drowsiness, blurred vision, slurred speech, difficulty walking, loss of consciousness, vertigo, confusion, disorientation, feeling drunk and shortness of breath [2][1].

For other drugs, the label has no separate drug-interactions section. Its only enzyme statement is in vitro: ketoconazole inhibited progesterone metabolism by human liver microsomes with an IC50 below 0.1 micromolar, and the label says this suggests that ketoconazole or other known CYP3A4 inhibitors may increase progesterone bioavailability, with the clinical relevance unknown [1]. The label does not name CYP3A4 inducers [1].

What bleeding data does the label give after the last dose?

The label's withdrawal-bleeding data come from a study of premenopausal women with secondary amenorrhea: 10 days of Prometrium 300 mg per day produced withdrawal bleeding within 7 days of the last dose in 80% of 20 women, against 10% of 21 women on placebo [2]. That is a different population and a higher dose than the 200 mg, 12-days-per-cycle menopause regimen [2].

What does the label's endometrial trial show for estrogen without Prometrium?

In the label's 36-month endometrial trial, 358 postmenopausal women with a uterus received conjugated estrogens 0.625 mg with cyclic Prometrium 200 mg, conjugated estrogens alone, or placebo. Hyperplasia by 36 months occurred in 6% (7 of 117) with the combination, 64% (74 of 115) with estrogen alone and 3% (3 of 116) with placebo; atypical hyperplasia 1%, 12% and 0% [2]. The trial measured three years of treatment, not the weeks of a surgical hold [2].