Drug Interactions between amoxicillin / clarithromycin / lansoprazole and sirolimus protein-bound

GENERALLY AVOID: Coadministration of protein-bound sirolimus intravenous suspension with potent inhibitors of CYP450 3A4 and/or P-glycoprotein (P-gp) may significantly increase the systemic exposure to sirolimus, which is a known substrate for both the isoenzyme and efflux transporter. No formal studies evaluating the drug interaction potential of protein-bound sirolimus have been conducted. However, significant increases in systemic exposure have been reported for oral sirolimus coadministered with potent inhibitors of CYP450 3A4 and/or P-gp such as azole antifungal agents and protease inhibitors. When a single 5 mg dose of sirolimus was administered with the potent dual CYP450 3A4/P-gp inhibitor ketoconazole (200 mg/day orally for 10 days) in healthy study subjects, mean sirolimus peak plasma concentration (Cmax) and systemic exposure (AUC) increased by approximately 4- and 11-fold, respectively. Likewise, the potent CYP450 3A4 inhibitor posaconazole (400 mg oral suspension twice a day for 16 days) increased mean Cmax and AUC of a single 2 mg dose of sirolimus by nearly 7- and 9-fold, respectively, while the potent CYP450 3A4 inhibitor voriconazole (400 mg orally every 12 hours for 1 day, then 200 mg every 12 hours for 8 days) increased the same values by 7- and 11-fold, respectively. The dual CYP450 3A4/P-gp inhibitor, boceprevir (800 mg three times a day for 11 days), increased the Cmax and AUC of a single 2 mg dose of sirolimus by 10- and 17-fold, respectively. Another dual CYP450 3A4/P-gp inhibitor, telaprevir (1125 mg every 12 hours), increased the dose-normalized Cmax and AUC of sirolimus in ten liver transplant patients by 3- and 26-fold, respectively. Increased exposures to sirolimus may increase the risk of adverse effects such as stomatitis, nausea, diarrhea, vomiting, myelosuppression, infections, hypokalemia, hyperglycemia, interstitial lung disease, edema, rash, alopecia, and hemorrhage.

MANAGEMENT: Concomitant use of protein-bound sirolimus with potent CYP450 3A4 and/or P-gp inhibitors should generally be avoided.

MONITOR: Coadministration with clarithromycin may increase the plasma concentrations of lansoprazole. The proposed mechanism is clarithromycin inhibition of intestinal (first-pass) and hepatic metabolism of lansoprazole via CYP450 3A4. Although lansoprazole is primarily metabolized by CYP450 2C19 in the liver, 3A4-mediated metabolism is the predominant pathway in individuals who are 2C19-deficient (approximately 3% to 5% of the Caucasian and 17% to 20% of the Asian population). Additionally, inhibition of P-glycoprotein intestinal efflux transporter by clarithromycin may also contribute to the interaction, resulting in increased bioavailability of lansoprazole. In 18 healthy volunteers--six each of homozygous extensive metabolizers (EMs), heterozygous EMs, and poor metabolizers (PMs) of CYP450 2C19--clarithromycin (400 mg orally twice a day for 6 days) increased the peak plasma concentration (Cmax) of a single 60 mg oral dose of lansoprazole by 1.47, 1.71- and 1.52-fold, respectively, and area under the concentration-time curve (AUC) by 1.55-, 1.74- and 1.80-fold, respectively, in each of these groups compared to placebo. The AUC ratio of lansoprazole to lansoprazole sulphone, which is considered an index of CYP450 3A4 activity, was significantly increased by clarithromycin in all three groups. However, elimination half-life of lansoprazole was prolonged by 1.54-fold only in PMs. Mild diarrhea was reported in two subjects and mild abdominal disturbance in six subjects during clarithromycin coadministration. These side effects continued until day 6 and ameliorated the day after discontinuation of clarithromycin, whereas no adverse events were reported during placebo administration or after lansoprazole plus placebo. In another study, clarithromycin induced dose-dependent increases in the plasma concentration of lansoprazole in a group of 20 patients receiving treatment for H. pylori eradication. Mean 3-hour plasma lansoprazole concentration was 385 ng/mL for the control subjects who received lansoprazole 30 mg and amoxicillin 750 mg twice a day for 7 days; 696 ng/mL for patients coadministered clarithromycin 200 mg twice a day; and 947 ng/mL for patients coadministered clarithromycin 400 mg twice a day.

MANAGEMENT: Although lansoprazole is generally well tolerated, caution may be advised during coadministration with clarithromycin, particularly if higher dosages of one or both drugs are used. Dosage adjustment may be necessary in patients who experience excessive adverse effects of lansoprazole.

Although some in vitro data indicate synergism between macrolide antibiotics and penicillins, other in vitro data indicate antagonism. When these drugs are given together, neither has predictable therapeutic efficacy. Data are available for erythromycin, although theoretically this interaction could occur with any macrolide. Except for monitoring of the effectiveness of antibiotic therapy, no special precautions appear to be necessary.