Drug interactions
Promethazine + Terbinafine
Severity: Moderate
Promethazine and Terbinafine: 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
Terbinafine is a strong CYP2D6 inhibitor and can raise promethazine concentrations, since promethazine is partly cleared by CYP2D6. This may increase sedation, anticholinergic effects and other dose-related adverse effects.
What this interaction means in plain words
Promethazine and Terbinafine 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.
Promethazine belongs to Respiratory; Terbinafine belongs to Anti Fungals.
Why it happens
Terbinafine inhibits CYP2D6-mediated metabolism of promethazine, reducing its clearance.
What to do
Monitor for excessive sedation, confusion and anticholinergic effects, and reduce the promethazine dose if these occur. Counsel patients about impaired psychomotor performance.
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 Terbinafine
- Terbinafine + Thioridazine Contraindicated
- Desipramine + Terbinafine Major
- Eliglustat + Terbinafine Major
- Flecainide + Terbinafine Major
- Imipramine + Terbinafine Major
- Maprotiline + Terbinafine Major
Frequently asked questions
Can I take Promethazine with Terbinafine?
MediHelp rates the interaction as moderate. Promethazine and Terbinafine 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. Terbinafine is a strong CYP2D6 inhibitor and can raise promethazine concentrations, since promethazine is partly cleared by CYP2D6. This may increase sedation, anticholinergic effects and other dose-related adverse effects.
How serious is the interaction between Promethazine and Terbinafine?
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 for excessive sedation, confusion and anticholinergic effects, and reduce the promethazine dose if these occur. Counsel patients about impaired psychomotor performance.
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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