Drug interactions
Efavirenz + Larotrectinib
Severity: Major
Efavirenz and Larotrectinib: major 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
Efavirenz can lower larotrectinib concentrations and may reduce tumor control. Larotrectinib is mainly cleared by CYP3A4, so induction is clinically relevant.
What this interaction means in plain words
Efavirenz and Larotrectinib 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.
Efavirenz belongs to Anti Virals; Larotrectinib belongs to Oncology.
Why it happens
Efavirenz induces CYP3A4, increasing larotrectinib metabolism.
What to do
Avoid the combination if possible. If unavoidable, double the larotrectinib dose and return to the usual dose after the inducer has been stopped for about 3 to 5 half-lives.
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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Other interactions of Efavirenz
- Cobimetinib + Efavirenz Contraindicated
- Dienogest / estradiol valerate + Efavirenz Contraindicated
- Dihydroergotamine intranasal + Efavirenz Contraindicated
- Dihydroergotamine + Efavirenz Contraindicated
- Doravirine + Efavirenz Contraindicated
- Efavirenz + Elbasvir / grazoprevir Contraindicated
Other interactions of Larotrectinib
Frequently asked questions
Can I take Efavirenz with Larotrectinib?
MediHelp rates the interaction as major. Efavirenz and Larotrectinib 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. Efavirenz can lower larotrectinib concentrations and may reduce tumor control. Larotrectinib is mainly cleared by CYP3A4, so induction is clinically relevant.
How serious is the interaction between Efavirenz and Larotrectinib?
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 possible. If unavoidable, double the larotrectinib dose and return to the usual dose after the inducer has been stopped for about 3 to 5 half-lives.
What other medicines interact with Efavirenz?
MediHelp also lists interactions of Efavirenz with, for example, Cobimetinib, Dienogest / estradiol valerate, Dihydroergotamine intranasal. The full list is on the Efavirenz page.
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