The generic name of Viagra is Sildenafil Citrate Tablets and the generic name of Elidel is Vardenafil Hydrochloride Tablets, and the difference between the two lies in the drug ingredients, contraindications, and adverse reactions. Sildenafil Citrate Tablets and Vardenafil Hydrochloride Tablets are both drugs for treating erectile dysfunction in men, but the drug ingredients are different, the former is mainly made of Sildenafil Citrate and the latter is made of Vardenafil Hydrochloride. In addition, the former is prohibited for those who are allergic to the product, and prohibited with regular or intermittent nitrate drugs or guanylate cyclase agonists; the latter in addition to the previous contraindications, but also prohibited with HIV protein kinase inhibitors (such as indinavir or ritonavir), prohibited for those who have lost their eyesight due to some kind of optic neuropathy, patients with severe liver damage and other conditions. Common adverse effects of the former include back pain, myalgia, hot flashes, headache, nasal congestion, dyspepsia, abnormal vision, nausea, dizziness and rash, while those of the latter include headache, dyspepsia, vasodilatation, dizziness and nasal congestion. Specific medication should be administered under the guidance of a specialist.