Drug interactions
Hyoscyamine spray + Promethazine
Severity: Moderate
Hyoscyamine spray 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
Hyoscyamine given as an oral or sublingual spray is absorbed systemically and adds to the anticholinergic burden of promethazine. This can produce dry mouth, constipation, urinary retention, tachycardia and confusion.
What this interaction means in plain words
Hyoscyamine spray 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 effects at muscarinic receptors.
What to do
Monitor for anticholinergic adverse effects and reduce doses if they develop. Avoid in patients with glaucoma, urinary retention or ileus, and use extra care in the elderly.
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
Frequently asked questions
Can I take Hyoscyamine spray with Promethazine?
MediHelp rates the interaction as moderate. Hyoscyamine spray 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. Hyoscyamine given as an oral or sublingual spray is absorbed systemically and adds to the anticholinergic burden of promethazine. This can produce dry mouth, constipation, urinary retention, tachycardia and confusion.
How serious is the interaction between Hyoscyamine spray 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 adverse effects and reduce doses if they develop. Avoid in patients with glaucoma, urinary retention or ileus, and use extra care in the elderly.
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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