Oral/Sublingual Medications: Sildenafil (Viagra), Vardenafil (Levitra), Tadalafil (Cialis), and Avenafil: Oral or sublingual medications work directly on the blood vessels, causing the arteries to the penis to expand. It can cause an erection when the man is sexually aroused.
Potential Side Effects: Headaches, facial flushing, backache, congestion, upset stomach, bluish tinge to vision or abnormal vision, hearing loss, and prolonged erections (priapism). These drugs cannot be taken with nitrates due to the possibility of decrease blood pressure. Caution should be used with Alpha blockers for prostate enlargement and/or high blood pressure due to the possibility of decreased blood pressure.