Drug interactions
Efavirenz + Primidone
Severity: Moderate
Efavirenz and Primidone: 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
Primidone, and its metabolite phenobarbital, induce hepatic enzymes and can lower efavirenz concentrations. This may lead to loss of virologic suppression and resistance. Efavirenz may also alter anticonvulsant levels.
What this interaction means in plain words
Efavirenz and Primidone 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.
Efavirenz belongs to Anti Virals; Primidone belongs to Central Nervous System.
Why it happens
Primidone and phenobarbital induce CYP3A4 and CYP2B6, accelerating efavirenz metabolism.
What to do
Monitor HIV viral load and, if available, efavirenz concentrations. Also monitor anticonvulsant levels and seizure control, or choose a non-inducing anticonvulsant.
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 Efavirenz
- Cobimetinib + Efavirenz Contraindicated
- Dienogest / estradiol valerate + Efavirenz Contraindicated
- Dihydroergotamine intranasal + Efavirenz Contraindicated
- Dihydroergotamine + Efavirenz Contraindicated
- Doravirine + Efavirenz Contraindicated
- Efavirenz + Elbasvir / grazoprevir Contraindicated
Other interactions of Primidone
- Lorlatinib + Primidone Contraindicated
- Lurasidone + Primidone Contraindicated
- Primidone + Ranolazine Contraindicated
- Primidone + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
- Primidone + Voriconazole Contraindicated
- Abiraterone + Primidone Major
Frequently asked questions
Can I take Efavirenz with Primidone?
MediHelp rates the interaction as moderate. Efavirenz and Primidone 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. Primidone, and its metabolite phenobarbital, induce hepatic enzymes and can lower efavirenz concentrations. This may lead to loss of virologic suppression and resistance. Efavirenz may also alter anticonvulsant levels.
How serious is the interaction between Efavirenz and Primidone?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor HIV viral load and, if available, efavirenz concentrations. Also monitor anticonvulsant levels and seizure control, or choose a non-inducing anticonvulsant.
What other medicines interact with Efavirenz?
MediHelp also lists interactions of Efavirenz with, for example, Cobimetinib, Dienogest / estradiol valerate, Dihydroergotamine intranasal. The full list is on the Efavirenz page.
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