How to take tablets Swallow tablets whole with a drink of water or juice but not grapefruit juice. Shake the liquid well for 10 seconds before each use to mix the medication evenly. The orodispersible tablets should be placed on the tongue and left to disintegrate before swallowing. What special precautions should I follow? The most common side effects with Viagra are headache, flushing, dyspepsia indigestion , visual disorders, including visual colour distortion and blurred vision, nasal congestion blocked nose , dizziness, nausea and hot flushes. Sexual stimulation is still needed to produce an erection.If you buy sildenafil for erectile dysfunction, it can also be known by the brand names Viagra, Aronix, Liberize and Nipatra. Sildenafil for pulmonary hypertension can also be known by the brand names Revatio and Grandipam. This medicine is available on prescription and you can also buy it from most pharmacies. 1. How it works Sildenafil may be used to treat erectile dysfunction (ED or impotence) in men (Viagra brand) or pulmonary arterial hypertension in both men and women (Revatio . Generic Viagra (sildenafil) is available as a , , , and milligram (mg) pill and in liquid form. It’s meant to be taken as needed — about an hour before sex — but shouldn’t be.