Drug interactions
Fosphenytoin + Progesterone
Severity: Moderate
Fosphenytoin and Progesterone: moderate interaction.
Last updated
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
Phenytoin, released from fosphenytoin, induces CYP3A4 and can lower progesterone levels, reducing its effect. This matters for contraception, endometrial protection and pregnancy support.
What this interaction means in plain words
Fosphenytoin and Progesterone can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fosphenytoin belongs to Central Nervous System; Progesterone belongs to Endocrine.
Why it happens
CYP3A4 induction by phenytoin increases progesterone metabolism.
What to do
Use a non-hormonal or alternative contraceptive method, and monitor for loss of progestogen effect. Increase the progesterone dose only if clinically indicated.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Progesterone
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fosphenytoin with Progesterone?
MediHelp rates the interaction as moderate. Fosphenytoin and Progesterone can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenytoin, released from fosphenytoin, induces CYP3A4 and can lower progesterone levels, reducing its effect. This matters for contraception, endometrial protection and pregnancy support.
How serious is the interaction between Fosphenytoin and Progesterone?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use a non-hormonal or alternative contraceptive method, and monitor for loss of progestogen effect. Increase the progesterone dose only if clinically indicated.
What other medicines interact with Progesterone?
MediHelp also lists interactions of Progesterone with, for example, Apalutamide, Carbamazepine, Enzalutamide. The full list is on the Progesterone page.
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