Finasteride and Minoxidil are the most prevalent medications for the treatment of hair loss. 

Rogaine (Minoxidil) and Propecia (Finasteride) are effective only at the early stages of thinning, during the period of hair miniaturization (gradual shrinking of hair). In the totally bald areas of the scalp, these medicines have no remarkable action. For this reason, one should start hair loss treatment with Rogaine or Propecia as soon as possible.

These medicines can be effective only in the case that someone wishes to preserve the existing hair. But they cannot restore hair in completely bald areas.
In many cases, Rogaine or Propecia treatments are combined with hair restoration surgery. Hair transplantation restores hair in bald areas of the scalp while medicines help encourage growth on thinning areas. 

ROGAINE(MINOXIDIL)

Rogaine is the first FDA approved hair loss treatment and it is available in concentration of 5% for men and 2% for women in the active ingredient of Minoxidil. Rogaine is used as topical solution that is applied directly to the scalp.

Rogaine has been clinically proven to help stimulate hair growth but it can be more effective when used in combination with Propecia.
Minoxidil was first used as a high blood pressure medicine, but it was also noticed to be effective in hair loss treatment. It has no significant effects in totally bald areas of the scalp or in the frontal hairline. It can help promote hair growth in thinning areas of the scalp.
One needs to use Rogaine for 6 months minimum before seeing the first signs of results. Maximum results can be observed within 2 years from the beginning of the treatment. Then, the rate of effectiveness slows down.

The exact action mechanism of Rogaine has not been completely ascertained, but the most possible explanation is that it revitalizes hair follicles and prolongs Anagen Phase. Rogaine also increases blood flow to the scalp and encourages gradual enlargement of miniaturized hair follicles.
Once one stops using Rogaine, any results that may have been obtained will be lost within the following 6 months. Rogaine can be effective in hair regrowth only if used continuously.  
 
Rogaine is also labelled for the treatment of hair loss in women, only in the concentration of 2%, as the female organism is more sensitive to its side effects (falling blood pressure, hair growth on the face, higher possibility to undergo dermatological allergy).           


PROPECIA (FINASTERIDE)

It is the only FDA approved (1997) pill for the treatment of male pattern hair loss. Propecia is available in concentration of 1mg in the active ingredient of Finasteride. Finasteride was initially approved as a treatment for prostate enlargement with the brand name Proscar (5mg tablets).

Mechanism of action: Propecia blocks the enzyme 5-a reductase, which is responsible for the transformation of testosterone to dihydrotestosterone (DHT). DHT is the androgen responsible for androgenetic alopecia in men.
The decrease in dihydrotestosterone levels suppresses hair loss and invigorates hair. But there is no positive effect on totally balding areas of the scalp. Propecia is more effective in the vertex and less in the frontal line and only if it is continuously received. Results can be noticed after at least 1 year of use and concern 20% of those who receive the treatment.

As for side effects, there have been some not always irreversible side effects -with a limited frequency and to a small percentage of people- such as decreased libido, sexual disorder etc.
Once one stops using Propecia, any results that may have been obtained will be lost as it can be effective in hair regrowth only through continued use.  

One should be thoroughly informed by a doctor before deciding on starting hair loss treatment with Minoxidil or Finasteride and take into account all possible side effects.