Drug interactions
Lofexidine + Promethazine
Severity: Moderate
Lofexidine 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
Lofexidine, a central alpha-2 agonist, causes sedation, hypotension and bradycardia, and it can also prolong the QT interval. Adding promethazine increases drowsiness and the risk of low blood pressure, and adds to QT risk.
What this interaction means in plain words
Lofexidine 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.
Lofexidine belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression and hypotension, with additive QT-prolonging potential.
What to do
Monitor sedation, blood pressure, heart rate and ECG, particularly when other QT-prolonging drugs are present. Correct electrolyte abnormalities and consider a non-sedating alternative for nausea.
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 Lofexidine
- Adagrasib + Lofexidine Major
- Alfuzosin + Lofexidine Major
- Amiodarone + Lofexidine Major
- Amisulpride + Lofexidine Major
- Anagrelide + Lofexidine Major
- Apomorphine + Lofexidine Major
Frequently asked questions
Can I take Lofexidine with Promethazine?
MediHelp rates the interaction as moderate. Lofexidine 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. Lofexidine, a central alpha-2 agonist, causes sedation, hypotension and bradycardia, and it can also prolong the QT interval. Adding promethazine increases drowsiness and the risk of low blood pressure, and adds to QT risk.
How serious is the interaction between Lofexidine 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 sedation, blood pressure, heart rate and ECG, particularly when other QT-prolonging drugs are present. Correct electrolyte abnormalities and consider a non-sedating alternative for nausea.
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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