Cialis, chemically known as tadalafil tablets, is a type 5 phosphodiesterase inhibitor and is a commonly used drug in clinical practice for the treatment of erectile dysfunction in men. It can inhibit the activity of phosphodiesterase, thus increasing the concentration of guanosine cyclic phosphate, leading to the relaxation of penile smooth muscle, resulting in a significant increase in arterial blood flow in the penile corpus cavernosum and thus improving erectile function. Tadalafil belongs to the long-acting class 5 phosphodiesterase inhibitors, the drug can be taken within 36 hours to freely choose the time of sex, is not affected by high-fat diet and moderate alcohol consumption, safety is relatively high, better tolerated.