- Use of nitrates, alfa blockers, vasodilators, ketoconazole, itraconazole, ritonavir, saquinavir, telithromycin, nefazodone, nelfinavir, atazanavir, cimetidine, erithromicin, clarithromycin, fluconazole, amprenavir, fosamprenavir, aprepitant, verapamil, diltiazem, any kind of vasodilator, antiplatelet, anticoagulant, dapoxetine, PDE5 inhibitor, alcohol and stimulant drug,