Sildenafil Azithromycin

Drugs that may affect nelfinavir include anticonvulsants, azithromycin, azole antifungals, efavirenz, delavirdine, HMG-CoA reductase inhibitors, indinavir, interleukins, nevirapine, rifabutin, rifampin, ritonavir, saquinavir, St. John s wort. Drugs that may be affected by nelfinavir include amiodarone, antiarrhythmics (amiodarone, quinidine), azithromycin, benzodiazepines, efavirenz, ergot alkaloids, delavirdine, didanosine, fentanyl, indinavir, lamivudine methadone, nonsedating antihistamines, oral contraceptives, phenytoin, pimozide, quinidine, rifabutin, saquinavir, sildenafil, sirolimus, tacrolimus, zidovudine. 

Erythromycin raises sildenafil levels almost threefold and raises vardenafil levels fourfold. Clarithromycin raises sildenafil levels about twofold. Erythromycin is predicted to similarly raise tadalafil levels. Azithromycin does not interact with sildenafil. 

In a study in 24 healthy subjects, erythromycin 500 mg twice daily for 5 days was found to increase the AUC of single 100-mg doses of sildenafil almost threefold. In the same study, azithromycin 500 mg once daily for 3 days had no effect on the pharmacokinetics of sildenafil. In another study, in 12 healthy subjects, clarithromycin 500 mg increased the AUC of sildenafil 50 mg 2.3-fold, and the maximum level 2.4-fold. ... 

Sildenafil, tadalafil and vardenafil are all metabolised by the cytochrome P450 isoenzyme CYP3A4. Many macrolides are moderate inhibitors of this isoenzyme and therefore inhibit sildenafil, tadalafil and vardenafil metabolism, which leads to increased levels of the phosphodiesterase inhibitors. Azithromycin does not usually act as a CYP3A4 inhibitor and therefore does not interact. 

Muirhead GJ, Faulkner S, Harness Taubel J. The effects of steady-state erythromycin and azithromycin on the pharmacokinetics of sildenafil citrate in heal volunteers. Br J Clin Pharmacol (2002) 53,37S-43S. 

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See also in sourсe #XX -- [ ]

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