In the wall of the intestine and liver sirolimus is subjected to extensive metabolism under the action of isoenzyme CYP3A4. Besides, sirolimus is a substrate for the localized in the small intestine P-glycoprotein (P-gp), which removes many drugs. Therefore, substances that act on these proteins, can affect the absorption of sirolimus and its subsequent elimination. Inhibitors CYP3A4 (ketoconazole, voriconazole, itraconazole, telithromycin or clarithromycin) reduce the metabolism of sirolimus, which leads to an increase in its concentration. Inductors of isoenzyme CYP3A4 (rifampicin or rifabutin) increase the metabolism of sirolimus, reducing its concentration. It is not recommended to appoint sirolimus simultaneously with powerful inducers or inhibitors CYP3A4 (see section "Special instructions").
Ciclosporin (substrate for CYP3A4): Cyclosporin A significantly increases the rate and degree of absorption of sirolimus. Simultaneous reception of Rapamun in a dose of 5 mg, then 5 mg in 2 hours and 10 mg in 4 hours after the appointment of 300 mg of a microemulsion of cyclosporine A led to an increase AUC sirolimus will bring about 80%,
respectively.The effect of the action of cyclosporin A appeared in the increase Сmах and Tmax sirolimus. If sirolimus was taken 2 hours prior to administration of the cyclosporin A microemulsion, no effect was observed on AUC and Cmax sirolimus. In healthy volunteers who received a single dose of sirolimus simultaneously with cyclosporine (microemulsion) or at a 4-hour interval, the pharmacokinetics of cyclosporin A did not change. It is recommended to appoint Rapamun 4 hours after taking a cyclosporine microemulsion.
Rifampicin (inducer CYP3A4): Multiple administration of rifampicin reduced the concentration of sirolimus in the blood after a single dose of 10 mg
Rapamun, solution for oral administration. Rifampicin increased the clearance of sirolimus by approximately 5.5 times and reduced AUC sirolimus and Cmax, approximately 82 and 71%, respectively. It is not recommended to appoint sirolimus simultaneously with rifampicin.
Ketoconazole (inhibitor CYP3A4): The repeated administration of ketoconazole significantly altered the rate, the degree of absorption and the effect of sirolimus: as indicated by a 4,4-, 1,4- and 10,9-fold increase, respectively, Cmax, Tmax and AUC. It is not recommended to appoint sirolimus concomitantly with ketoconazole.
^ Voriconazole (inhibitor CYP3A4): When combined in healthy volunteers, sirolimus (2 mg once) and voriconazole (400 mg intravenously every 12 hours on the first day, then 100 mg every 12 hours for 8 days), an average 7-fold increase in Cmax and 11-fold increase AUC sirolimus. It is not recommended to appoint sirolimus concomitantly with voriconazole.
Diltiazem (inhibitor CYP3A4): With the simultaneous administration of 10 mg of Rapamun in the form of a solution for oral administration and 120 mg of diltiazem, the bioavailability of sirolimus significantly changed. Cmax, Tmax and AUC sirolimus increased, respectively, in 1.4, 1.3 and 1.6 times. Sirolimus did not change the pharmacokinetics of diltiazem and its metabolites-
deacetyl-dithiasem and desmethyldiltiazem. When appointing diltiazem it is necessary to control the concentration of sirolimus in the blood and, if necessary, adjust the dose of the drug.
Verapamil (inhibitor CYP3A4): With the appointment of multiple doses of verapamil and sirolimus in the form of a solution for oral administration, the rate and degree of absorption of both drugs varied significantly. Cmax, Tmax and AUC sirolimus in whole blood increased, respectively, in 2,3, 1,1 and 2,2 times. Cmax value, and AUC S - (-) verapamil in plasma increased by 1.5 times, and Tmax was reduced by 24%. It is necessary to control the concentrations of sirolimus and, if necessary, to reduce the doses of both drugs accordingly.
Erythromycin (inhibitor CYP3A4): With the appointment of multiple doses of erythromycin and sirolimus in the form of a solution for oral administration, the rate and degree of absorption of both compounds increased significantly. Cmax, Tmax and AUC sirolimus in whole blood increased, respectively, 4.4, 1.4 and 4.2 times. Cmax, Tmax and AUC erythromycin in the plasma increased, respectively, in 1.6, 1.3 and 1.7-fold. Need to monitor
concentration of sirolimus and, if necessary, reduce the doses of both drugs accordingly.
Oral contraceptives: There were no clinically significant pharmacokinetic interactions between sirolimus and 0.3 mg norgestrel / 0.03 mg ethinylestradiol. Although the results of the study of the interaction of a single dose of Rapamun with an oral contraceptive indicate a lack of pharmacokinetic interaction, long-term treatment with Rapamun can not exclude possible changes in pharmacokinetics that may affect the effectiveness of oral contraceptives.
Other possible interactions: Moderate and weak inhibitors CYP3A4 can reduce the metabolism of sirolimus and increase the concentration of sirolimus in the blood (for example, blockers of slow calcium channels:
nicardipine; antifungal agents: clotrimazole, fluconazole; antibiotics: troleandomycin; and other drugs: bromocriptine, cimetidine, danazol, protease inhibitors).
Inductors CYP3A4 can accelerate the metabolism of sirolimus and reduce the concentration of sirolimus in the blood, (for example, a medicinal plant St. John's Wort - Hyperisum perforatum; anticonvulsants: carbamazepine, phenobarbital, phenytoin).
Although in vitro sirolimus inhibits the activity of isoenzymes of the microsomal system of cytochrome P450 in humans (CYP2C9, CYP2C19, CYP2D6, CYP3A4 / 5), suppression of the activity of these isoenzymes in vivo is unlikely, since for this, the sirolimus concentration should be significantly higher than in patients receiving the drug in therapeutic doses. Inhibitors P-gp can reduce the release of sirolimus from intestinal cells and help increase its concentration in the blood.
Grapefruit juice affects CYP3A4 mediated metabolism and, therefore, it should not be consumed while taking Rapamun.
Pharmacokinetic interaction can be observed with gastrointestinal prokinetic agents such as cisapride, metoclopramide.
There was no clinically significant pharmacokinetic interaction of sirolimus with acyclovir, atorvastatin, digoxin, glibenclamide, methylprednisolone, nifedipine, prednisolone, and trimethoprim / sulfamethoxazole.
With the simultaneous use of Rapamun with calcineurin inhibitors, an increased risk of hemolytic-uremic syndrome / thrombocytopenic thrombotic purpura / thrombotic microangiopathy induced by calcineurin inhibitors is possible.