If you are taking tadalafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. The medication should be taken once daily at about the same time every day to maintain a consistent level of medicine in the body. This condition may require prompt medical treatment to prevent serious and permanent damage to your penis. When using this medicine for erectile dysfunction, the ability to have sexual activity may be improved for up to 36 hours after taking the tablet. If you will be taking this medicine for pulmonary arterial hypertension, it is very important that your doctor check your progress at regular visits. Dosing is as follows: As needed for ED: 5 to 20 mg by mouth as a one-time dose, with a maximum of one dose in 24 hours. Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection.What is the price of Cialis 20 mg? expand_more. With Goodrx, the generic version of Cialis 20 mg (tadalafil) is about $9 for 10 tablets. The brand version is about $ Five tablets of Cialis 10 mg is about $ with GoodRx. The generic version is more affordable at about $6 for the same strength and quantity. Yes, because tadalafil (Cialis) works by relaxing your blood vessels, it can lower your blood pressure. But your blood pressure shouldn’t drop by too much. In clinical studies, people who took the 20 mg dose of tadalafil (Cialis) experienced an average drop in blood pressure by about 2 mm Hg. CrCl 31 to 80 mL/min: 20 mg orally once a day. Increase to 40 mg orally once a day based on individual tolerability. CrCl less than 30 mL/min and on hemodialysis: Use should be avoided. Liver Dose Adjustments. Use as needed for ED: Mild to moderate hepatic dysfunction (Child-Pugh Class A and B): 10 mg orally once a day.