Viagra generally refers to sildenafil citrate tablets, and regardless of which manufacturer produces this medication, its efficacy is similar and there is no difference between good and bad. Sildenafil citrate tablets are generally used for the treatment of erectile dysfunction, which improves the ability of men to have an erection. Regardless of which manufacturer produces this drug, its clinical efficacy is tested and meets the national standard, there is no obvious difference, not good or bad. The most frequent adverse reactions to this product include nasal congestion, dyspepsia, nausea, rash, dizziness, headache, back pain, myalgia, etc. It is contraindicated in people with a known allergy to this product and in patients taking nitrate drugs. It is recommended to purchase and take the medication as prescribed by a physician, and should not be used blindly.