If you take nitrates in any form, or are on treatment for pulmonary hypertension , you should not take tadalafil. You should only be treated with one of these products at a time. Patients should seek prompt medical attention if their erection lasts longer than four hours. It may be taken with or without food. The decision of availability is completely up to the company marketing the product. Will Cialis be prescription or OTC over-the-counter? If you are taking tadalafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph.20mg. No data.. Quantity. 5. 6. No data.. Read More About This Drug. Tadalafil – STADA T20 – 20 Milligramm. Tadalafil, sold under the brand name Cialis among others, is a medication used to treat erectile dysfunction, benign prostatic hyperplasia, and pulmonary arterial hypertension. It is taken by mouth. Onset is typically within half an hour and the duration is up to 36 hours. Common side effects include headache, muscle pain, . A manufacturer coupon or copay card is not available for Cialis. However, GoodRx discounts are available to help make it more affordable. Tadalafil, the generic version of Cialis is available for about $9 for 30 tablets of the 5 mg strength.