Long-Term Safety Profile of Tadalafil in Female Patients

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Efficacy rates for the PDE-5 inhibitors vary widely throughout the literature with a range of 57% to 83%.5,11-13 Additionally, they have all shown efficacy in the treatment of ED in men with diabetes mellitus; however, no particular agent has yet to be recommended for patients with cardiovascular disease.2,8,10,12,14,15 Comparative trials are required to determine if a specific agent possesses better efficacy. There are drug-drug interactions with each of these medications, many of which involve the same drugs due to CYP 3A4 being the major enzymatic pathway for all of these agents. Due to the potential for severe hypotension, sildenafil and organic nitrates (e.g., nitroglycerin, isosorbide dinitrate [Isordil®, Sorbitrate®], and isosorbide mononitrate [Imdur, ISMO®, Monoket®]) are contraindicated (i.e., should not be taken together), and sildenafil doses > 25 mg should not be used within 4 hours of taking an alpha-blocker (e.g., prazosin [Minipress®], terazosin [Hytrin®], and doxazosin [Cardura®]). Sildenafil is a substrate of CYP 3A4 and 2C8/9 as well as an inhibitor of CYP 1A2, 2C8/9, 2C19, 2D6, 2E1, and 3A4; therefore, increased effects and possible toxicity of sildenafil occur when used concomitantly with drugs that inhibit these enzymes (e.g., cimetidine [Tagamet®], erythromycin, ketoconazole [Nizoral®], itraconazole [Sporanox®], amprenavir [Agenerase®], indinavir [Crixivan®], saquinavir [Fortovase®], and ritonavir [Norvir®]). Enzyme-inducing agents, such as St. opposite effect and cause decreased sildenafil levels.