Drug interactions
Levonorgestrel + Nafcillin
Severity: Moderate
Levonorgestrel and Nafcillin: 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
Nafcillin has been shown to induce CYP3A4 and may lower exposure to hormonal contraceptives. The clinical effect on contraceptive failure is poorly documented, and for an intrauterine system the local effect likely limits the impact.
What this interaction means in plain words
Levonorgestrel and Nafcillin 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.
Why it happens
Nafcillin induces CYP3A4, which increases levonorgestrel clearance.
What to do
For oral or emergency levonorgestrel, advise an additional barrier method during nafcillin therapy and for a short period afterward. No action is generally needed for an intrauterine system.
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 Levonorgestrel
Frequently asked questions
Can I take Levonorgestrel with Nafcillin?
MediHelp rates the interaction as moderate. Levonorgestrel and Nafcillin 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. Nafcillin has been shown to induce CYP3A4 and may lower exposure to hormonal contraceptives. The clinical effect on contraceptive failure is poorly documented, and for an intrauterine system the local effect likely limits the impact.
How serious is the interaction between Levonorgestrel and Nafcillin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: For oral or emergency levonorgestrel, advise an additional barrier method during nafcillin therapy and for a short period afterward. No action is generally needed for an intrauterine system.
What other medicines interact with Levonorgestrel?
MediHelp also lists interactions of Levonorgestrel with, for example, Amobarbital, Apalutamide, Belzutifan. The full list is on the Levonorgestrel page.
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