Tadalafil (Cialis): A phosphodiesterase type 5 inhibitor for the treatment of benign prostatic hyperplasia

On October 6, 2011, FDA approved tadalafil once-daily 5-mg oral tablet for the treatment of benign prostatic hyperplasia (BPH) in patients with or without erectile dysfunction (ED). Tadalafil is a phosphodiesterase type 5 inhibitor, which allows for the increase of cyclic guanosine monophosphate (cGMP), not only in the corpus cavernosum (for ED), but also the smooth muscle of the prostate, bladder, and their vascular supply.

Efficacy. The efficacy of tadalafil was determined in 3 randomized, multinational, double-blinded, placebo-controlled, parallel-design, efficacy and safety studies of 12 weeks duration. Two of these studies were in men with BPH, and the other was specific to men with both ED and BPH. In the first BPH study, participants were randomly assigned to receive 2.5 mg, 5 mg, 10 mg, or 20 mg of tadalafil once daily or placebo (n=1,058). In the second, 325 participants were randomly assigned to receive 5 mg of tadalafil once daily or placebo. In both trials, tadalafil 5 mg resulted in statistically significant improvement in total International Prostate Symptom Score (IPSS) compared to placebo, starting as early as week 4 and continuing through week 12 (-4.8 vs -2.2, P<.001 for study 1, and -5.6 vs -3.6, P=.004 for study 2). In the BPH plus ED study (n=606) patients were randomly assigned to receive tadalafil 2.5 mg or 5 mg daily or placebo. Again, tadalafil 5 mg showed a statistically significant improvement in IPSS (-6.1 vs -3.8, P<0.001) and ED symptoms compared to placebo.

Safety. During clinical trials, the most common adverse events in participants receiving tadalafil 5 mg daily included headache (11%), dyspepsia (4%), back pain (3%), nasal congestion (2%), flushing (2%), myalgia (1%), and limb pain (1%). Tadalafil is contraindicated in patients using organic nitrates regularly or intermittently, due to potential hyposensitive effects resulting in decreased blood pressure. Tadalafil should not be administered with alpha blockers or substantial amounts of alcohol (≥5 drinks) as this may also cause hypotension and low blood pressure. Patients should stop taking tadalafil and seek medical attention if a sudden loss of vision or hearing occurs. Patients should not use tadalafil if sex is inadvisable due to cardiovascular status.