Since the early 1990s, medications such as a-blockers or 5a-reductase inhibitors have been developed. If you are prescribed oral medication, you may have to take daily tablets for a certain period of time from a few months to a few years in order to maintain improvement of the symptoms. Drug therapy relieves symptoms in about 70 to 80% of the patients under oral medication. Side effects may include: impotence, dizziness, headaches and fatigue.
Several types of agents are used in oral therapy :

• a-adrenergic blocking agents (Terazosin). Part of the prostate is made of smooth muscle tissue (involuntary muscle) that is controlled by a-adrenergic receptors (nerves). Alpha blockers may make urination easier by relaxing this smooth muscle tissue.
• 5a-reductase inhibitor (Finasteride).This hormone suppressor shrinks the prostate by reducing the effect of the hormones that stimulate prostate growth. The active substance, the Finasteride, blocks the conversion of testosterone to dihydrotestosterone and usually reduces the prostate size by 20 to 25% over a period of 6 months. Due to the nature of the medication, this treatment generally takes 4 to 6 months to take effect.
• Phytotherapy. Phytotherapy recently became a more popular treatment option among men with BPH. These pharmaceutical products are derived from plant extracts and do not require a prescription. The most popular herbal agents are Saw Palmeto (Serenoa repens), Pygeum Arficanum and Beta Sitosterol. Phytotherapeutic agents may lead to limited subjective and objective symptom relief.