Sildenafil as well as tadalafil are both medications that are more effective in treating erectile dysfunction in men. Tadalafil lasts a little longer. 1. Sildenafil: The effective blood concentration of sildenafil is maintained for 4-6 hours, which means that you need to have sex within 4-6 hours of taking the drug to improve erectile function. 2. Tadalafil: Tadalafil’s efficacy can last for 36 hours, which means that sexual intercourse within 36 hours after taking the drug can achieve the purpose of improving erection. Sildenafil and tadalafil are both prescription drugs with certain side effects and contraindications. Dizziness, headache, vomiting and other discomforts may occur after taking the drug. Overall, if you suffer from erectile dysfunction, it is recommended that you go to the hospital in time and use medication under the guidance of your doctor.