Drug interactions
Levocetirizine + Promethazine
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.
Overview
Additive H1-antihistamine effects increase risk of sedation, impaired psychomotor performance, and anticholinergic adverse effects (e.g., dry mouth, constipation, urinary retention), particularly in older adults.
Mechanism of action
Pharmacodynamic: combined H1-receptor antagonism and anticholinergic effects.
Clinical management
Avoid duplicate H1-antihistamine therapy when possible; select a single agent. If coadministered, use the lowest effective doses, avoid alcohol and other CNS depressants, caution patients about driving/operating machinery, and monitor for anticholinergic toxicity (especially in elderly, BPH, glaucoma).
Drug reference
References
- Promethazine: Drug Information (including Drug Interactions) — Lexicomp
- Levocetirizine: Drug Information (including Drug Interactions) — Lexicomp
- Antihistamines: Adverse effects and drug interactions — UpToDate
- Phenergan (promethazine hydrochloride) Prescribing Information — FDA Label
- Xyzal (levocetirizine dihydrochloride) Prescribing Information — FDA Label
Frequently asked questions
Can I take Levocetirizine with Promethazine?
The interaction is rated: Moderate. Additive H1-antihistamine effects increase risk of sedation, impaired psychomotor performance, and anticholinergic adverse effects (e.g., dry mouth, constipation, urinary retention), particularly in older adults.
How serious is the interaction between Levocetirizine and Promethazine?
The interaction is rated: Moderate. Evidence level: Moderate.
How is the interaction between Levocetirizine and Promethazine managed?
Avoid duplicate H1-antihistamine therapy when possible; select a single agent. If coadministered, use the lowest effective doses, avoid alcohol and other CNS depressants, caution patients about driving/operating machinery, and monitor for anticholinergic toxicity (especially in elderly, BPH, glaucoma).
Why do Levocetirizine and Promethazine interact?
Pharmacodynamic: combined H1-receptor antagonism and anticholinergic effects.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.