Drug interactions
Isoproterenol + Promethazine
Severity: Moderate
Isoproterenol 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 has some alpha-adrenergic blocking activity, and phenothiazines can cause tachycardia and QT prolongation. Together with isoproterenol, a potent beta agonist that causes tachycardia and vasodilation, this may increase heart rate and hypotension and the risk of arrhythmia in susceptible patients. The clinical evidence is limited.
What this interaction means in plain words
Isoproterenol 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.
Isoproterenol belongs to Respiratory; Promethazine belongs to Respiratory.
Why it happens
Additive cardiovascular effects, combining alpha-blockade and QT liability with beta-agonist-induced tachycardia and vasodilation; not fully characterized.
What to do
Monitor heart rate, blood pressure and ECG when the two are given together. Correct hypokalemia and hypomagnesemia, and use the lowest effective isoproterenol dose.
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
Other interactions of Isoproterenol
Frequently asked questions
Can I take Isoproterenol with Promethazine?
MediHelp rates the interaction as moderate. Isoproterenol 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 has some alpha-adrenergic blocking activity, and phenothiazines can cause tachycardia and QT prolongation. Together with isoproterenol, a potent beta agonist that causes tachycardia and vasodilation, this may increase heart rate and hypotension and the risk of arrhythmia in susceptible patients. The clinical evidence is limited.
How serious is the interaction between Isoproterenol 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 heart rate, blood pressure and ECG when the two are given together. Correct hypokalemia and hypomagnesemia, and use the lowest effective isoproterenol dose.
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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