It works by increasing blood flow to the penis during sexual stimulation. Your doctor will probably start you on an average dose of vardenafil tablets and increase or decrease your dose depending on your response to the medication. However, the dose is usually not more than 20 mg once per day. Before taking vardenafil, tell your doctor and pharmacist if you are allergic to vardenafil,any other medications. An erection will not occur just by taking a pill. Ask your doctor if you are not sure if any of your medications contain nitrates.Side effects of oral ED medicines are often mild. Common ones include: Flushing of the skin. Headache. Upset stomach. Visual changes, such as blue tinge to vision, sensitivity to light or blurred sight. Stuffy or runny nose. Back pain. Dizzy feeling.  · The penis is one of the areas where this enzyme works. Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. When a man is sexually stimulated, his body’s normal response is to increase blood flow to his penis to produce an erection.  · chest pain, discomfort, or tightness chest tightness or heaviness chills cold sweats confusion decreased vision difficult or labored breathing difficulty with swallowing dizziness dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position eye pain fainting.