Drug interactions
Lonafarnib + Primaquine
Severity: Major
Lonafarnib and Primaquine: major interaction.
Last updated Sources: Health Canada product monograph
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
Lonafarnib is a sensitive CYP3A substrate and primaquine is a weak CYP3A inhibitor, so lonafarnib exposure may rise. Higher lonafarnib levels may increase gastrointestinal toxicity and the risk of arrhythmia.
What this interaction means in plain words
Lonafarnib and Primaquine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Lonafarnib belongs to Miscellaneous; Primaquine belongs to Anti Parasitic.
Why it happens
Weak CYP3A inhibition by primaquine reduces lonafarnib clearance.
What to do
Avoid the combination if an alternative is available. If not, keep lonafarnib at the starting dose and monitor for arrhythmia symptoms, syncope and palpitations.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Primaquine
- Pimozide + Primaquine Contraindicated
- Amiodarone + Primaquine Major
- Amisulpride + Primaquine Major
- Anagrelide + Primaquine Major
- Arsenic trioxide + Primaquine Major
- Asenapine + Primaquine Major
Other interactions of Lonafarnib
- Alfuzosin + Lonafarnib Contraindicated
- Amobarbital + Lonafarnib Contraindicated
- Apalutamide + Lonafarnib Contraindicated
- Bosentan + Lonafarnib Contraindicated
- Carbamazepine + Lonafarnib Contraindicated
- Clarithromycin + Lonafarnib Contraindicated
Frequently asked questions
Can I take Lonafarnib with Primaquine?
MediHelp rates the interaction as major. Lonafarnib and Primaquine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Lonafarnib is a sensitive CYP3A substrate and primaquine is a weak CYP3A inhibitor, so lonafarnib exposure may rise. Higher lonafarnib levels may increase gastrointestinal toxicity and the risk of arrhythmia.
How serious is the interaction between Lonafarnib and Primaquine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if an alternative is available. If not, keep lonafarnib at the starting dose and monitor for arrhythmia symptoms, syncope and palpitations.
What other medicines interact with Primaquine?
MediHelp also lists interactions of Primaquine with, for example, Pimozide, Amiodarone, Amisulpride. The full list is on the Primaquine page.
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