Medicines that block an enzyme called CYP3A4. These are commonly prescribed for an enlarged prostate or male pattern baldness. Vardenafil usually works for 4 to 5 hours. It might work longer if you have mild to moderate erectile dysfunction. These medicines all work well for ED. Patients should always ask their doctors for medical advice about adverse events. This medication is taken with or without food an hour before sex.Viagra is an effective drug for treating male erectile dysfunction, but it targets sexual performance, not sexual arousal. There is limited evidence that Viagra may be beneficial for women with sexual dysfunction, but the . What is Viagra? Viagra is a brand-name prescription drug that’s approved to treat erectile dysfunction (ED). With ED, you’re unable to have or maintain an erection. Viagra is approved for.  · a light-headed feeling, like you might pass out. Common sildenafil side effects may include: flushing (warmth, redness, or tingly feeling); headache, dizziness; heartburn, nausea, or upset stomach. abnormal vision (blurred vision, changes in color vision) runny or stuffy nose, nosebleeds; sleep problems (insomnia); or.