Drug interactions
Loxapine + Promethazine
Severity: Moderate
Loxapine 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
Both agents block dopamine receptors, so combined use raises the risk of extrapyramidal symptoms and, rarely, neuroleptic malignant syndrome. They also add to sedation, anticholinergic effects, hypotension and QT prolongation.
What this interaction means in plain words
Loxapine 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.
Loxapine belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive dopamine D2 antagonism, sedation, anticholinergic activity and QT-prolonging effects.
What to do
Monitor for rigidity, tremor, fever, altered mental status and ECG changes. Avoid the combination in patients with QT risk factors or prior neuroleptic malignant syndrome, or use a non-dopamine-blocking antiemetic.
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 Loxapine
- Alfentanil + Loxapine Major
- Alprazolam + Loxapine Major
- Amisulpride + Loxapine Major
- Amoxapine + Loxapine Major
- Apomorphine + Loxapine Major
- Belladonna and opium + Loxapine Major
Frequently asked questions
Can I take Loxapine with Promethazine?
MediHelp rates the interaction as moderate. Loxapine 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. Both agents block dopamine receptors, so combined use raises the risk of extrapyramidal symptoms and, rarely, neuroleptic malignant syndrome. They also add to sedation, anticholinergic effects, hypotension and QT prolongation.
How serious is the interaction between Loxapine 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 for rigidity, tremor, fever, altered mental status and ECG changes. Avoid the combination in patients with QT risk factors or prior neuroleptic malignant syndrome, or use a non-dopamine-blocking antiemetic.
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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