Drug interactions
Anticholinergic / sedative combos + Promethazine
Severity: Moderate
Anticholinergic / sedative combos 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
Promethazine's own anticholinergic and sedative properties add to those of belladonna-type combination products. This may cause marked drowsiness, confusion, dry mouth, urinary retention and constipation.
What this interaction means in plain words
Anticholinergic / sedative combos 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.
Why it happens
Additive antimuscarinic and CNS depressant effects.
What to do
Monitor for anticholinergic toxicity and sedation, particularly in older adults. Reduce doses or choose a non-anticholinergic alternative if adverse effects occur.
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
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Frequently asked questions
Can I take Anticholinergic / sedative combos with Promethazine?
MediHelp rates the interaction as moderate. Anticholinergic / sedative combos 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. Promethazine's own anticholinergic and sedative properties add to those of belladonna-type combination products. This may cause marked drowsiness, confusion, dry mouth, urinary retention and constipation.
How serious is the interaction between Anticholinergic / sedative combos 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 anticholinergic toxicity and sedation, particularly in older adults. Reduce doses or choose a non-anticholinergic alternative if adverse effects occur.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine page.
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