There are only 2 drugs which are approved by FDA of USA for treatment of hair loss and I have tried both when I was young. Both can stop hair loss and regrow hair a bit in my case. Do not expect miracle overnight and it takes 3 to 6 months for improvement to appear. If you stop using the drug later, hair loss will reappear.
The liquid drug for external use is called Minoxidil 5% solution and is available in ebay US for roughly US$5 per bottle of 60ml. which can be used for a month. Postage is extra. You can find it in Yahoo HK as well but is more expensive. The other drug is Propecia 保康x (1 mg) which is in pill form for internal use and is 10 times more expensive. For some men, it may cause impotence and therefore is not recommended for young men who wants to have kids. If you like to try the pill but consider it too expensive, you can buy Proscar which is the same thing but 5 mg each and one quarter the price of Propecia. Just cut the pill into 4 to 5 parts and you have a home made Propecia. Proscar is for the treatment of enlarged prostate but men receiving it also grow more hair. By reducing the dosage to 1 mg, it is found effective in treating hair loss in men and thus the birth of Propecia.
No other drug or hair solution has been tested in USA to be effective in stopping hair loss and therefore do not buy them even if their advertisements are impressive. You are just wasting your money. Scientists are still struggling to find a drug to treat hair loss and the first one to find such a drug will find a gold mine too. Just like the first appearance of Viagra.
Declaration of Interest -- I have stopped using both since hair loss is no longer a concern to me because I am now old enough to disregard it.