The generics cost much less, and—in the case of sildenafil—come in 20 mg doses. This medicine also works best when you take it an hour before sex on an empty stomach. That makes it difficult to have a romantic dinner before adjourning to the bedroom. Its effects often last for 4 to 5 hours. Often, these are prescribed for chest pain called angina. · a light-headed feeling, like you might pass out. Common sildenafil side effects may include: flushing (warmth, redness, or tingly feeling); headache, dizziness; . 25 rows · Compare risks and benefits of common medications used for Erectile . Sildenafil oral tablet is available as a brand-name drug and as a generic drug. Brand names: Viagra, Revatio. Sildenafil comes in three forms: an oral tablet, an .