Viagra is the trade name, generic name of sildenafil, and tadalafil can not be taken at the same time, belongs to the same class of drugs, taking at the same time belongs to the repeated use of drugs. Sildenafil and tadalafil, both belong to the selective type 5 phosphodiesterase inhibitors, the same class of drugs can not be taken at the same time, otherwise it will result in repeated use of medication may affect the health of the body, and even cause other adverse reactions. It is mainly used to treat male erectile dysfunction, which requires sexual stimulation to be effective. Sildenafil and tadalafil use may cause abdominal pain, nausea, vomiting, headache, dizziness, increased heart rate, facial flushing and other adverse reactions. It is prohibited for those who are allergic to the drug; it is prohibited during the taking of nitrate drugs. It is recommended to go to the hospital for examination first, and the drug needs to be used under the guidance of professional doctors.