Generic name of Cialis is Tadalafil and generic name of Viagra is Sildenafil Citrate, both of them are able to treat erectile dysfunction of sexual function but may cause skin flushing, indigestion and so on. 1. Tadalafil Advantages: It can improve erectile dysfunction after taking it. 2. Tadalafil Disadvantages: After taking it, it often shows headache, facial flushing, nasal congestion, nasopharyngitis, back pain, myalgia, dyspepsia, etc. Sometimes it can cause allergic reaction or low blood pressure. 3. Sildenafil Advantages: Sildenafil has the effect of vasodilatation, which can treat pulmonary arterial hypertension, and can also make the penis congested and improve the situation of erectile dysfunction. 4. Sildenafil Disadvantages: Taking this drug may lead to drug allergy, lower blood pressure, skin flushing, indigestion and so on. If impotence occurs, it is recommended to go to a regular hospital to find a professional doctor for treatment, and the drug needs to be applied reasonably according to medical advice.