Forzest 20 mg contains tadalafil 20 mg and is marketed by Sun Pharmaceutical Industries Ltd. It is a prescription PDE5 inhibitor used primarily for erectile dysfunction (ED); tadalafil is also used for certain urinary symptoms associated with benign prostatic hyperplasia (BPH). For ED, tadalafil improves blood flow to the penis during sexual stimulation, helping achieve and maintain an erection. A 20 mg dose is the usual maximum recommended as-needed dose for ED. It should not be taken more than once daily. Tadalafil may remain effective for up to 36 hours after an as-needed dose.