Sildenafil tablets efficacy and effect is mainly to promote penile erection, contraindications include allergic to the product, etc., specific medication as prescribed by the doctor. Sildenafil tablets can treat erectile dysfunction, mainly through selective inhibition of PDE5, enhance the nitric oxide (NO)-cGMP pathway, elevate the level of cGMP and lead to the relaxation of the cavernous smooth muscle of the penis, so that patients with erectile dysfunction to the sexual stimulation to produce a natural erectile response. The drug should be contraindicated in people who are allergic to the product, who are using guanylate cyclase agonists (e.g., leucovorin), or who are taking regular or intermittent use of nitric oxide donors (e.g., any form of organic nitrites or organic nitrates). Common adverse reactions to the drug include indigestion, rash, myalgia, hot flashes (bouts of fever), back pain, abnormal vision, nasal congestion, nausea, headache, and dizziness. Sildenafil tablets should be administered under the specific guidance of a physician.