There are several pills and lotions currently available.

Finasteride 1 mg is available with a prescription. It reduces the amount of Di Hydro Testosterone, a male hormone that may be responsible for hair loss. It does not affect the main male hormone, Testosterone. The main reported side effect is a decrease in sexual drive in 2% of patients.
Finasteride 5 mg has been prescribed for some 10 years to patients with prostatomegaly. It was well tolerated in patients aged between 50 and 70.
Finasteride 1 mg can be effective in the early stages of androgenetic alopecia, more so on the crown than the front of the scalp.

Minoxidil lotion is available at 2% and 5% and has been used for more than 10 years. It has to be applied twice a day on the scalp without interruption. There are no reported side effects other than minor irritation in some patients. Minoxidil is more effective at preventing hair loss than regrowing lost hair.

Finasteride and Minoxidil must be used for life. If application is interrupted or stopped, hair loss will recur.