Drug interactions
Primidone + Promethazine
Severity: Moderate
Primidone and Promethazine: 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 is an anticonvulsant metabolized to phenobarbital and causes sedation. Combined with promethazine, CNS depression increases, and promethazine may also lower the seizure threshold.
What this interaction means in plain words
Primidone and Promethazine 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 belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression; phenothiazines may lower seizure threshold and primidone/phenobarbital induces enzymes.
What to do
Monitor sedation and seizure control, and advise caution with driving. Adjust anticonvulsant therapy if seizure frequency increases.
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 Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
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 Primidone with Promethazine?
MediHelp rates the interaction as moderate. Primidone and Promethazine 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 is an anticonvulsant metabolized to phenobarbital and causes sedation. Combined with promethazine, CNS depression increases, and promethazine may also lower the seizure threshold.
How serious is the interaction between Primidone and Promethazine?
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 sedation and seizure control, and advise caution with driving. Adjust anticonvulsant therapy if seizure frequency increases.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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