Viagra and Viagra are the same drug, Viagra is the common name, Viagra is the trade name, the generic name is sildenafil, so there is no which one is better. Sildenafil is a phosphodiesterase 5 inhibitor, which enhances the nitric oxide (NO)-cGMP pathway through selective inhibition of PDE5, elevating cGMP levels and leading to relaxation of penile cavernous smooth muscle, so that patients with erectile dysfunction produce a natural erectile response to sexual stimulation. Clinically, it is mainly used in the treatment of male erectile dysfunction. The main adverse reactions of sildenafil are cardiovascular reactions, such as hot flashes, angina, tachycardia, hypotension, myocardial ischemia, heart failure, etc.; metabolic abnormalities, such as elevated blood glucose, elevated blood uric acid, elevated blood sodium, decreased blood potassium, etc.. In addition, the respiratory system, the skeletal muscle system, the nervous system and other reactions may occur, but generally mild. It should be noted that sildenafil is contraindicated in patients with hypersensitivity to the drug, patients with severe hepatic impairment, patients with recent stroke, patients with hereditary retinal degeneration. Sildenafil can promote penile erection, but requires a certain amount of sexual stimulation to be effective, and does not have the effect of delaying and enhancing sexual desire. Use must be strictly grasp the contraindications, and monitor the adverse effects, if any discomfort, promptly to the hospital.