Indeed, doses over mg have shown no increased advantages for treating ED, and they raise the risk of side effects — and this would typically be outside the terms of the product license in any case. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. Side effects Side effects of oral ED medicines are often mild. Numerous clinical trials have demonstrated that Viagra is a very safe drug, and most men have a positive experience of the treatment. A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow.Viagra is used to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve exercise . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles . Sildenafil (Viagra) increases blood flow to the penis so that you can get an erection. But it may cause side effects, including light sensitivity and diarrhea. Certain side effects may .