The Food and Drug Administration (FDA) has now approved the erectile dysfunction drug tadalafil (Cialis) to treat the signs and symptoms of benign prostatic hyperplasia (BPH) and as a treatment for BPH and erectile dysfunction when they occur together.

Tadalafil promotes smooth muscle relaxation and increased blood flow by inhibiting phosphodiesterase type 5 (PDE5), an enzyme that stops the vasodilating activity of cyclic guanosine monophosphate (cGMP). Without PDE5's effects, cGMP can continue to promote smooth muscle relaxation and vasodilation. In addition to being active in the penile tissue, PDE5 is active against cGMP in the prostate; inhibiting the enzyme's action provides relaxation of the prostate. The exact mechanism by which tadalafil treats the signs and symptoms of BPH hasn't been determined. The dosage for treating BPH or BPH with erectile dysfunction is 5 mg daily.

Drug interactions from tadalafil are the same regardless of the indication for which it's prescribed. Common adverse effects are flushing, headache, dyspepsia, back pain, myalgia, nasal congestion, and limb pain. Tadalafil shouldn't be administered with nitrates because a significant drop in blood pressure may occur, and [alpha] blockers, such as terazosin (Hytrin), doxazosin (Cardura), tamsulosin (Flomax), alfuzosin (Uroxatral), and silodosin (Rapaflo), which are often used in the treatment of BPH, can also increase the risk of hypotension.

Nurses should be aware of this new indication for tadalafil and provide appropriate patient education. They should also assess the patient's drug profile for nitrates or [alpha] blockers. To read the complete prescribing information, see http://1.usa.gov/tD46dU.