Irinotecan and Rifampin interaction
Irinotecan and Rifampin: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Irinotecan (Camptosar) label · effective 2026-05-12
• Strong CYP3A4 Inducers: Do not administer strong CYP3A4 inducers with CAMPTOSAR.
Do not administer strong CYP3A4 inducers with CAMPTOSAR unless there are no therapeutic alternatives.
The appropriate starting dose for patients taking these or other strong inducers such as rifampin and rifabutin has not been defined.
Strong CYP3A4 Inducers Exposure to irinotecan or its active metabolite SN-38 is substantially reduced in adult and pediatric patients concomitantly receiving the CYP3A4 enzyme-inducing anticonvulsants phenytoin, phenobarbital, carbamazepine, or St.
Consider substituting non-enzyme inducing therapies at least 2 weeks prior to initiation of CAMPTOSAR therapy.
From the Rifampin label · effective 2026-05-05
Doxycycline Administered with rifampin (10 mg/kg daily) Decrease exposure Irinotecan Administered with an antibiotic regimen including rifampin (450 mg/day), isoniazid (300 mg/day), and streptomycin (0.5 g/day) IM Prevention or Management: Avoid the use of rifampin, a strong CYP3A4 inducer, if possible.
Substitute non-enzyme inducing therapies at least 2 weeks prior to initiation of irinotecan therapy Decrease irinotecan and active metabolite exposure Levothyroxine Decrease exposure Losartan Parent Decrease AUC by 30% Active metabolite (E3174) Decrease AUC by 40% Methadone In patients well-stabilized on methadone, concomitant administration of rifampin resulted…
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.