In , Pfizer scientists discovered that sildenafil, which also inhibits the PDE5 enzyme, caused penile erection in males participating in a clinical study of a heart medicine. Tell your doctor if any of these symptoms are severe or do not go away: headache. Will Cialis be prescription or OTC over-the-counter? Erectile Dysfunction, though, is when your difficulty with getting an erection or staying hard becomes a regular occurrence. If you are taking tadalafil to treat PAH or BPH, follow your doctor’s directions and the guidelines in this paragraph. Take tadalafil exactly as directed.MNT ‘s review. Lemonaid sells Cialis in these forms: Cialis: available in doses of 5, 10, and 20 mg, starting at $65 per tablet. Daily Cialis: 5 mg tablet with pricing starting from $50 per tablet. Transfer your prescription for Tadalafil (Generic for Cialis, Oral Tablet) on Amazon Pharmacy. FREE SHIPPING for Prime members. 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. [4] [5] [7] It is taken by mouth. [7] Onset is typically within half an hour and the duration is up to 36 hours.