There are some potential interactions with other medications. Please tell your doctor if you are taking the following 5 classes of drugs:
NITRATES: DO NOT TAKE Viagra if you are currently taking any medicines containing nitrates, such as nitroglycerin for chest pain. Whether you take the nitrates once daily or every now and then, DO NOT TAKE Viagra.
Alpha Blockers: Let your doctor know if you have high blood pressure or if you have issues with your prostate. Medications that treat these problems are called alpha blockers. In these scenarios, the doctor will most likely start you off with a lower dose.
Protease Inhibitors: Any drugs classified as protease inhibitors will also place some restrictions on the appropriate dosage for Viagra. Most likely, the patient will be limited to the lowest dose: 25 mg and coupled with a maximum of one dose per a 48 hour period. These class of drugs generally treat diseases such as HIV.
Revatio: This drug contains sildenafil, the same ingredient found in Viagra. Likes do not mix with likes!
Other Medications That Treat ED: Cialis (Tadalafil), Levitra (Vardenafil), and Staxyn (Vardenafil).