Drug interactions
Lumacaftor / ivacaftor + Promethazine
Severity: Minor
Lumacaftor / ivacaftor and Promethazine: minor 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
In vitro data suggest lumacaftor induces and ivacaftor inhibits CYP2B6, but promethazine is mainly metabolised by CYP2D6 and other pathways, so a meaningful effect is not established. There is no reliable clinical evidence of a significant interaction.
What this interaction means in plain words
Lumacaftor / ivacaftor and Promethazine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Why it happens
Theoretical CYP modulation by lumacaftor/ivacaftor; no established effect on promethazine clearance.
What to do
No dose adjustment is required; monitor for reduced or increased promethazine effect if clinically suspected.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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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 Lumacaftor / ivacaftor with Promethazine?
MediHelp rates the interaction as minor. Lumacaftor / ivacaftor and Promethazine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. In vitro data suggest lumacaftor induces and ivacaftor inhibits CYP2B6, but promethazine is mainly metabolised by CYP2D6 and other pathways, so a meaningful effect is not established. There is no reliable clinical evidence of a significant interaction.
How serious is the interaction between Lumacaftor / ivacaftor and Promethazine?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No dose adjustment is required; monitor for reduced or increased promethazine effect if clinically suspected.
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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