Before taking tadalafil, tell your doctor and pharmacist if you are allergic to tadalafil, any other medications, or any of the ingredients in tadalafil tablets. This increased blood flow can cause an erection. Ask your pharmacist for a list of the ingredients. Tadalafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow more easily. How should this medicine be used?Doctors usually recommend starting with a mg dose and moving up to 20 mg if a stronger dose is needed to achieve the desired results. Price and dosage: Generic Cialis (tadalafil): $8 per. Cialis: mg, 5 mg, 10 mg, and 20 mg, taken as needed. The cost of the medication is from $ per month for Cialis and from $40 per month for tadalafil. Online . The price of tadalafil may depend on the strength. Tadalafil comes in strengths of milligrams (mg), 5 mg, 10 mg, and 20 mg. As with other drugs, the cost of tadalafil depends on several factors.