Possible Interaction: Irinotecan and St John's Wort

“These findings indicate that patients on irinotecan treatment should refrain from taking SJW because plasma levels of SN-38 were dramatically reduced, which may have a deleterious impact on treatment outcome.”

“ Hypericum extract , by inducing both the CYP3A4 and the P-glycoprotein (P-gp), can reduce the plasma concentrations of different antineoplastic agents such as imatinib, irinotecan and docetaxel, thus reducing the clinical efficacy of these drugs.”

“A clinical study in cancer patients reported that treatment of St John's wort at 900 mg/day orally for 18 days decreased the plasma levels of the active metabolite of irinotecan , SN-38, by 42%.”

“For example, a clinical study in cancer patients reported that treatment of St John's wort at 900 mg/day orally for 18 days decreased the plasma levels of the active metabolite of irinotecan , SN-38, by 42%.”

“Results from clinical studies and case reports indicate that self-administered SJW reduce steady state plasma concentrations of amitriptyline, cyclosporine, digoxin, fexofenadine, amprenavir, indonavir, lopinavir, ritonavir, saquinavir, benzodiazepines, theophyline, irinotecan , midazolan and warfarin.”

“In clinical studies using midazolam or anticancer drugs irinotecan and imatinib) as known CYP3A4 substrates in combination with SJW , decreased plasma levels of these drugs were observed, which was expected as a consequence of CYP3A4 induction.”

“Clinical trials indicate …’s wort Hypericum perforatum ), via cytochrome P450 (CYP) and/or P-glycoprotein induction, reduces the plasma concentrations (and/… clearance) of alprazolam, amitriptyline, atorvastatin, chlorzoxazone, ciclosporin, debrisoquine, digoxin, erythromycin, fexofenadine, gliclazide, imatinib, indinavir, irinotecan , ivabradine, mephenytoin, methadone, midazolam, nifedipine, omeprazole, oral …, tacrolimus, talinolol, verapamil, voriconazole and warfarin.”

“A study in the Journal of the National Cancer Institute … 42% lower in the blood of patients who received irinotecan … St John’s wort than in the blood of patients who received irinotecan alone, leading the authors … cannot be given safely in combination without compromising overall anti-tumour activity”.”

“Such a relevant interaction is that of St. John's wort with the anticancer drugs irinotecan and imatinib.”