Viagra is the trade name and generic name of Sildenafil Citrate Tablets, which usually cannot be taken before Sildenafil Citrate Tablets and then Tadalafil Tablets. Sildenafil citrate tablets and tadalafil tablets are both used to treat erectile dysfunction in men, and if they are taken together before and after they may result in an overly strong effect, which can lead to adverse reactions. Sildenafil Citrate Tablet is mainly used for the treatment of erectile dysfunction. Adverse reactions after taking the drug include facial edema, fatigue, shock, allergic reaction, pain, chills, chest pain, abdominal pain, tachycardia, palpitations, low blood pressure, vomiting, and dysphagia. This product is contraindicated if patients are taking any dosage form of nitrate, and should also be contraindicated in patients who are allergic to any of the components of this product. Tadalafil tablets are also used for the treatment of erectile dysfunction in men, which requires sexual stimulation for the product to take effect, and common adverse reactions include headache, dyspepsia, dizziness, and nasal congestion. Patients who are allergic to this product and its ingredients are prohibited from taking it. Patients who need to take these two drugs should choose one under the guidance of a doctor, and should not take it on their own, so as not to aggravate the adverse effects of the drug.