Finasteride was originally developed to relieve symptoms associated with benign prostatic hyperplasia (BPH), an enlargement of the prostate gland common in men over 50.
While testing a 5 mg dose of the drug for those purposes in the early 1990s, unforeseen benefits for the retention and stimulation of hair growth on the head were observed.
The 5 mg dose went on to be approved for prostate treatment by the US Food and Drug Administration (FDA) and marketed by pharmaceuticals giant Merck as Proscar.
Further trials led to a 1 mg dose for hair loss entering the market branded as Propecia, when on 22 December 1997 Finasteride was approved by the FDA as the first clinically proven systemic treatment for male pattern baldness.
Finally men hoping to slow, stop or even reverse the process of balding had a successful pharmaceutical treatment at their disposal.
Available only with a doctor's prescription, Finasteride counters hair loss by chemically preventing the metabolism of testosterone into dihydrotestosterone (DHT) within the body.
It achieves this by targeting and inhibiting type II 5-alpha-reductase, one of two types of an enzyme able to facilitate such a conversion.
By interfering with this process Finasteride greatly reduces the amount of DHT present in, among other tissue in the body, the scalp.
The detrimental effect that DHT has on the vitality of the individual follicles and hairs of susceptible individuals can thus be negated, or more accurately, deferred.
Clinical studies indicate that anywhere from 2 out of 3 to 80% of men orally administered a 1 mg dose of Finasteride on a daily basis report some improvement from the treatment.
Results vary from successfully slowing down the balding process to stopping the loss of hair or stimulating new growth around the crown and top of the head.
Less success has been reported around the temples however, and ceasing the treatment will cause the process of hair loss to gradually resume until within 12 months any benefits afforded by Finasteride have been lost.
It is also unlikely to confer benefits on advanced cases of hair loss.
Younger men who have hair they would like to retain and are willing to make a long term commitment are likely to benefit the most from this treatment.
On the downside, possible side effects reported by a small proportion of men using Finasteride during trials have included abdominal pain, back pain, decreased libido and volume of ejaculate, impotence, dizziness, rash, swelling of the lips and face, breast tenderness and testicular pain.
Problems such as these cleared up after ceasing the treatment.
For many participating men who remained on Finasteride, side effects reduced or resolved during the course of their treatment.
Women who are or may become pregnant should not handle Finasteride (especially crushed tablets) due to a risk that the drug may cause birth defects in a male fetus.
Men using Finasteride should inform their doctor prior to taking a PSA (prostate-specific antigen) test for prostate cancer as the drug may interfere with results.
The use of Finasteride is banned in many sports as its presence in the blood can mask traces of steroid abuse.
In addition to its approved FDA status, Finasteride's popularity can be attributed to the fact that it is one of the most convenient measures against hair loss on the market.
Consumers will also be pleased that with the expiration of Merck's patents on Proscar and Propecia in June 2006, a range of generic Finasteride alternatives has begun to bring prices for the treatment down considerably.
A three month (90 tablet) run of 5 mg doses able to be cut into quarters with a pill cutter now costs anything from $116 (generic) to $409 (branded), making the cost of a daily dose of the drug a dollar a day or lower if consumers are prepared to shop around.