Take sildenafil at around the same times every day. How should this medicine be used? Taking sildenafil alone will not cause an erection. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. What side effects can this medication cause? It can be dangerous to take sildenafil if you also take medicines called nitrates often given for chest pain. Shake the liquid well for 10 seconds before each use to mix the medication evenly. · 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. Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. VIAGRA may affect the way other medicines work, and other medicines may affect the way VIAGRA works, causing side effects. Especially tell your healthcare provider if you take any of the following. Unlike pills like Vigrx Plus which are designed to work over a period of weeks / months, Extenze is a fast acting male enhancement alternative to viagra that works quickly, usually within 45 – 60 min. The original makers of Extenze actually got in a bit of trouble back when they first started selling it.