Prometrium and smoking: how tobacco affects the medication
Tobacco smoking is one of the most underappreciated drug-drug interactions in chronic medication. Compounds in tobacco smoke induce hepatic enzymes (especially CYP1A2) and can shift the plasma concentration of many medications, including Prometrium (Progesterone), enough to matter clinically at 100mg, 200mg.
How smoking affects Prometrium
Polycyclic aromatic hydrocarbons in tobacco smoke induce CYP1A2 and to a lesser extent other CYP enzymes. For medications metabolised primarily by CYP1A2, smokers can have plasma levels 30–50% lower than non-smokers at the same dose. Whether Progesterone is affected depends on its specific metabolic pathway. Progesterone in Prometrium binds to progesterone receptors and modulates gene expression in reproductive and other tissues.
Practical guidance
According to the prescribing information for Progesterone, smoking status should be disclosed at every dose review of Prometrium. Stopping smoking can paradoxically raise plasma levels of CYP1A2-metabolised medications enough to cause new-onset side effects within days, and may require a temporary dose reduction. The 100mg, 200mg starting strength assumed in the prescribing information is usually for non-smokers.
Frequently asked questions
Does smoking change how Prometrium works? ▾
For medications metabolised by CYP1A2, yes — smokers may need higher doses or have reduced effect at standard 100mg, 200mg. Whether Prometrium specifically is affected depends on whether Progesterone uses CYP1A2. The prescribing information notes any documented interaction.
Will I need to adjust Prometrium if I quit smoking? ▾
Possibly, if Prometrium is one of the medications affected by CYP1A2 induction. Stopping smoking restores CYP1A2 to normal within days, raising plasma levels and potentially causing side effects. Discuss the timing of any dose adjustment with the prescriber when planning to quit.
More on Prometrium
- With alcoholPrometrium and alcohol — is it safe to drink?
- With foodShould Prometrium be taken with food?
- Side effectsPrometrium side effects: common, rare and warning signs
- Dosage guidePrometrium dosage guide: how much to take and when
- OnsetHow fast does Prometrium start working?
- DurationHow long does Prometrium last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.