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Oral Micronized Progesterone and Nicotine: Full Interaction Profile

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At a glance

  • Interaction status / No interaction documented for the pair [1]
  • Smoke component that induces enzymes / Polycyclic aromatic hydrocarbons, not nicotine [2][3]
  • The only enzyme named in the label / CYP3A4, in an in-vitro ketoconazole note the label calls of unknown clinical relevance [1]
  • Nicotine cardiovascular effects / Peripheral vasoconstriction, faster heart rate, higher blood pressure [4]
  • Label contraindications that matter to a smoker / Active or past DVT or PE; active or past stroke or heart attack [5]
  • Boxed warning / None in the current Prometrium label [1][6]

What the Prometrium label says

Prometrium is oral micronized progesterone, labeled for preventing endometrial hyperplasia in postmenopausal women with a uterus who take conjugated estrogens tablets, and for secondary amenorrhea [5]. The label says progesterone is metabolized primarily in the liver, largely to pregnanediols and pregnanolones, without naming the enzyme responsible for that main pathway [1]. CYP3A4 appears once, in an in-vitro finding: ketoconazole inhibited progesterone metabolism by human liver microsomes, which the label says suggests that ketoconazole or other inhibitors of this enzyme may raise progesterone bioavailability, with the clinical relevance unknown [1].

Nicotine is not the smoke ingredient that changes liver enzymes

Polycyclic aromatic hydrocarbons in tobacco smoke are believed to be responsible for induction of CYP1A1 and CYP1A2, and possibly CYP2E1 [4]. Nicotine is not the inducer: a review of smoking-cessation interactions states the effect on hepatic microsomal enzymes is not related to the nicotine component of tobacco, so nicotine replacement will not alter it [3].

Animal work adds a caveat without changing that picture. In rats, a single nicotine dose raised lung CYP1A1 activity 4.4-fold at 6 hours and 14.7-fold at 12 hours, near baseline again by 24 hours, while liver CYP1A2 protein and mRNA were unaffected [7]. Human relevance is unknown.

Clotting-related label limits that matter to smokers

Nicotine produces peripheral vasoconstriction, tachycardia and higher blood pressure [4]. Separately, Prometrium's labeled contraindications include active DVT or pulmonary embolism or a history of either, and active arterial thromboembolic disease such as stroke or myocardial infarction or a history of it [5]. These are separate facts about each substance, listed side by side; they are not a documented combined effect.

The label directs stopping immediately if PE, DVT, stroke or MI occurs or is suspected, and says that, if feasible, Prometrium should be stopped at least 4 to 6 weeks before surgery associated with increased clot risk or during prolonged immobilization [5].

The Prometrium label summarizes a WHI trial (16,608 women in total, randomized to conjugated estrogens 0.625 mg plus medroxyprogesterone 2.5 mg, not micronized progesterone, or to placebo); average follow-up was 5.6 years [5]. It reported relative risks of 1.87 for DVT, 1.98 for PE, 1.37 for stroke, and 1.24 for invasive breast cancer [5].

The cigarette-smoking boxed warning on serious cardiovascular events belongs to combined hormonal contraceptives, which the Sprintec label contraindicates in women over 35 who smoke [8].

Frequently asked questions

Does nicotine interact with oral micronized progesterone?
No interaction is documented for the pair [1]. Nicotine is not the smoke component that induces liver enzymes; that effect is attributed to polycyclic aromatic hydrocarbons [2][3].
Do smokers need a different progesterone dose?
The label gives fixed regimens: 200 mg at bedtime for 12 days per 28-day cycle with conjugated estrogens, or 400 mg at bedtime for 10 days for secondary amenorrhea [5].
What happens to drug levels when someone stops smoking?
Enzyme induction fades. In 12 heavy smokers who stopped abruptly, caffeine clearance fell 36.1%, and the apparent half-life of the decline in CYP1A2 activity was 38.6 hours [9]. The effect is not related to nicotine, so nicotine replacement does not prevent it [3].
Is a nicotine patch or gum different from cigarettes here?
Yes for enzyme induction. The effect on hepatic enzymes is attributed to smoke components other than nicotine, and a review states nicotine replacement will not alter it [3][2]. Nicotine still has its own cardiovascular effects: vasoconstriction, tachycardia and higher blood pressure [4].
Can a smoker who has had a clot take Prometrium?
The label contraindicates Prometrium in women with active DVT or pulmonary embolism or a history of either, and in those with active arterial thromboembolic disease such as stroke or heart attack or a history of it [5]. It also says to stop immediately if PE, DVT, stroke or MI occurs or is suspected [1].
Does Prometrium have a boxed warning about smoking?
No. The current Prometrium label has no boxed warning; the cardiovascular, breast cancer and dementia boxed language was removed in the update FDA approved on 2026-02-12 [6][1]. The smoking boxed warning belongs to combined hormonal contraceptives [8].

References

  1. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  2. Kroon LA. Drug interactions with smoking. Am J Health Syst Pharm. 2007;64(18):1917-21. Drug interactions with smoking
  3. Schaffer SD, Yoon S, Zadezensky I. A review of smoking cessation: potentially risky effects on prescribed medications. J Clin Nurs. 2009;18(11):1533-40. A review of smoking cessation: potentially risky effects on prescribed medications
  4. Zevin S, Benowitz NL. Drug interactions with tobacco smoking. An update. Clin Pharmacokinet. 1999;36(6):425-38. Drug interactions with tobacco smoking. An update
  5. U.S. National Library of Medicine, DailyMed. Prometrium progesterone capsules (Acertis), Rev. 02/2026 prescribing information. Prometrium progesterone capsules (Acertis), Rev. 02/2026 label
  6. FDA Approves Labeling Changes to Menopausal Hormone Therapy Products | FDA. FDA Approves Labeling Changes to Menopausal Hormone Therapy Products | FDA
  7. Iba MM, Scholl H, Fung J, Thomas PE, Alam J. Induction of pulmonary CYP1A1 by nicotine. Xenobiotica. 1998;28(9):827-43. Induction of pulmonary CYP1A1 by nicotine
  8. U.S. National Library of Medicine, DailyMed. Sprintec (norgestimate and ethinyl estradiol) prescribing information. Sprintec (norgestimate and ethinyl estradiol) label
  9. Faber MS, Fuhr U. Time response of cytochrome P450 1A2 activity on cessation of heavy smoking. Clin Pharmacol Ther. 2004;76(2):178-84. Time response of cytochrome P450 1A2 activity on cessation of heavy smoking
Evidence overview for Oral Micronized Progesterone and Nicotine: Full Interaction Profile