Mavacamten and Estradiol Topical: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mavacamten
Estradiol Topical
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Reduced hormonal contraceptive exposure, reduced efficacy of hormonal contraceptive, increased mavacamten exposure and an increased risk of mavacamten-related adverse reactions
Interaction Deep Dive
Concomitant administration of mavacamten, a CYP3A4 inducer, and progestin and/or ethinyl estradiol, CYP3A4 substrates, may reduce exposures of progestin and ethinyl estradiol, which may lead to contraceptive failure. CHCs containing a combination of ethinyl estradiol and norethindrone may be used with mavacamten based on a clinical study, but if other CHCs are used, advise patients to add nonhormonal contraception (eg, condoms) during treatment with mavacamten and for 4 months after the last mavacamten dose. Concomitant use of mavacamten and weak CYP2C19 inhibitors may increase mavacamten exposure and may also increase efficacy of mavacamten. Initiate mavacamten at the recommended starting dosage of 5 mg orally once daily in patients who are on stable therapy with a weak CYP2C19 inhibitor. Reduce dose of mavacamten to the next lower daily (mg) dose (ie, 15 to 10 mg, 10 to 5 mg, or 5 to 2.5 mg) in patients who are on mavacamten treatment and intend to initiate a weak CYP2C19 inhibitor. Perform clinical and ECG assessment 4 weeks after inhibitor initiation, and do not up-titrate to the next higher daily (mg) dose level of mavacamten until 12 weeks after inhibitor initiation. Avoid initiation of concomitant weak CYP2C19 inhibitor in patients who are on stable treatment with 2.5 mg of mavacamten because a lower dose is not available. For short-term use (eg, 1 week), interrupt mavacamten for the duration of treatment with a weak CYP2C19 inhibitor. Mavacamten may be reinitiated at the previous dose immediately on discontinuation of concomitant therapy1.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism by mavacamten; inhibition of CYP2C19-mediated metabolism of mavacamten
Literature reports
3 reports — tap to read
a) No clinically significant differences in ethinyl estradiol and norethindrone exposure were observed in healthy female subjects with CYP2C19 NM phenotype following concomitant use of a combined oral contraceptive containing ethinyl estradiol and norethindrone with a 17-day course of mavacamten (25 mg on days 1 and 2, followed by 15 mg for 15 days). The impact of mavacamten on oral contraceptives containing other progestins is unknown 1.
b) In a drug interaction study, concomitant use of a 16-day course of the CYP3A4 inducer mavacamten (25 mg on days 1 and 2, followed by 15 mg for 14 days) with midazolam, a CYP3A4 substrate, resulted in a 13% decrease in midazolam AUC(inf) and a 7% decrease in Cmax, in healthy CYP2C19 normal metabolizers. Following coadministration of mavacamten once daily in patients with hypertrophic cardiomyopathy patients at the upper end of the therapeutic range, midazolam AUC (inf) and Cmax are predicted to decrease up to 45% and 24%, respectively 1.
c) In a drug interaction study, concomitant use of mavacamten 15 mg with omeprazole 20 mg once daily increased mavacamten AUC(inf) by 48% with no effect on Cmax in healthy CYP2C19 normal and rapid metabolizers 1.
Common questions
Can I take Mavacamten and Estradiol Topical together?
Reduced hormonal contraceptive exposure, reduced efficacy of hormonal contraceptive, increased mavacamten exposure and an increased risk of mavacamten-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mavacamten and Estradiol Topical interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Mavacamten or Estradiol Topical need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: CAMZYOS(R) oral capsules, mavacamten oral capsules. Bristol-Myers Squibb Company (per Manufacturer), Princeton, NJ, 2025. DailyMed
Keep reading about Mavacamten
Keep reading about Estradiol Topical
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