There are two different ways to take tadalafil, either daily or on an as needed basis. You may attempt sexual activity at any time between doses. Comparison with actions of other PDE5 inhibitors[ edit ] Sildenafil and vardenafil inhibit PDE6, an enzyme found in the eye, more than tadalafil. Cialis can also interact with other medications, including nitrates and blood pressure medications. Benign prostatic hypertrophy is a condition in which the prostate gland becomes enlarged, obstructing the free flow of urine. Your doctor will probably tell you not to take tadalafil if you are taking nitrates. Take all of the tablets for your daily dose at one time each day; do not divide the tablets to take as separate doses.Used for Benign Prostatic Hyperplasia, Erectile Dysfunction. erectile dysfunction (ED) benign prostatic hyperplasia, or BPH). Tadalafil (Cialis) is available both as brand-name and generic tablets. Common side effects of this medication include headache and indigestion. Tadalafil (Cialis) does interact with some medications.  · Cialis comes as a tablet that you swallow. It’s available in four strengths: milligrams (mg), 5 mg, 10 mg, 20 mg. Depending on your situation and what condition Cialis is treating, you’ll. Was this helpful? How does Cialis work? Cialis works by increasing blood flow to the penis to help a person get and maintain an erection. It also blocks the PDE5 enzyme, which enhances the.