VIAGRA and drug interactions.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

VIAGRA may affect the way other medicines work, and other medicines may affect the way VIAGRA works, causing side effects. Especially tell your healthcare provider if you take any of the following:

medicines called nitrates
medicines called alpha-blockers such as Hytrin (terazosin HCl), Flomax (tamsulosin HCl), Cardura (doxazosin mesylate), Minipress (prazosin HCl), Uroxatral (alfuzosin HCl), Jalyn (dutasteride and tamsulosin HCl), or Rapaflo (silodosin). Alpha-blockers are sometimes prescribed for prostate problems or high blood pressure. In some patients, the use of VIAGRA with alpha-blockers can lead to a drop in blood pressure or to fainting
medicines called HIV protease inhibitors, such as ritonavir (Norvir), indinavir sulfate (Crixivan), saquinavir (Fortovase or Invirase), or atazanavir sulfate (Reyataz)
some types of oral antifungal medicines, such as ketoconazole (Nizoral) and itraconazole (Sporanox)
some types of antibiotics, such as clarithromycin (Biaxin), telithromycin (Ketek), or erythromycin
other medicines that treat high blood pressure
other medicines or treatments for ED
VIAGRA contains sildenafil, which is the same medicine found in another drug called REVATIO. REVATIO is used to treat a rare disease called pulmonary arterial hypertension (PAH). VIAGRA should not be used with REVATIO or with other PAH treatments containing sildenafil or any other PDE5 inhibitors (such as Adcirca [tadalafil])