Drug interactions
Griseofulvin + Mestranol
Severity: Major
Griseofulvin and Mestranol: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Griseofulvin has been associated with breakthrough bleeding and contraceptive failure in users of estrogen-containing contraceptives. Mestranol is converted to ethinylestradiol, whose exposure may be reduced by enzyme induction.
What this interaction means in plain words
Griseofulvin and Mestranol can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Griseofulvin induces hepatic CYP3A4, increasing estrogen metabolism and lowering contraceptive hormone levels.
What to do
Advise an additional non-hormonal contraceptive method during griseofulvin therapy and for about a month afterwards. Counsel on breakthrough bleeding.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Griseofulvin
Frequently asked questions
Can I take Griseofulvin with Mestranol?
MediHelp rates the interaction as major. Griseofulvin and Mestranol can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Griseofulvin has been associated with breakthrough bleeding and contraceptive failure in users of estrogen-containing contraceptives. Mestranol is converted to ethinylestradiol, whose exposure may be reduced by enzyme induction.
How serious is the interaction between Griseofulvin and Mestranol?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Advise an additional non-hormonal contraceptive method during griseofulvin therapy and for about a month afterwards. Counsel on breakthrough bleeding.
What other medicines interact with Griseofulvin?
MediHelp also lists interactions of Griseofulvin with, for example, Cyclosporine, Cyclosporin, Desogestrel-ethinyl estradiol. The full list is on the Griseofulvin page.
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