Avodart contain the active ingredient Dutasteride, which is a type of medicine called a 5-alpha reductase inhibitor. Avodart works by inhibiting the action of a compound in the body called 5-alpha reductase. This compound is called an enzyme, and is responsible for converting the male hormone testosterone into dihydrotestosterone (DHT), which is a more active form of testosterone. The enlargement of the prostate gland, which often occurs in men with advancing age, is dependant upon testosterone being converted to DHT within the prostate gland. In the absence of DHT the prostate gland shrinks. By decreasing the amount of testosterone that is converted into DHT, dutasteride therefore helps to shrink the prostate gland.

The prostate gland is found only in men and lies at the top of the tube connecting the bladder to the outside (urethra). Enlargement of the prostate causes it to press on the urethra and bladder and can cause urinary symptoms such as difficulty passing urine and increased need to urinate, particularly at night. By shrinking the prostate, dutasteride relieves the pressure on the bladder and urethra. This allows urine to flow freely past the prostate and relieves the urinary symptoms associated with this condition.

Avodart is the most powerful treatment currently available for treating hair loss in men. Dutasteride is a substance similar to Propecia's Finasteride but considered to be a more powerful DHT blocker than Finasteride as it inhibits both types of 5-alpha reductase. It showed improved results versus finasteride, especially in the frontal area of the scalp, and it can be used successfully by patients who no longer respond to finasteride. Dutasteride can only be used by adult men.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Less serious side effects may include: decreased libido (sex drive), decreased amount of semen released during sex, impotence (trouble getting or keeping an erection), breast tenderness or enlargement. This is not a complete list of side effects and others may occur.