Finasteride sold under the brand name Propecia is a prescription drug sold in tablet form. It is the most effective medicine for strengthening hair and slowing down further loss. Some people who take the drug have also reported re-growth particularly around the crown area. This medication has bee proven to be by far the most effective and slowing down further hair loss and stabilising things before a transplant. In around 2% to 3% of patients have reported some side effects: impotence and decreased libido and mood swings. However, the studies are inclusive about this as subsequent studies using placebo tablets came back with the same results. I would definitely looking in to this if you are at risk of further hair loss.
Another popular treatment is Minoxidil, widely known as Regaine or Rogaine which is applied as a foam or lotion. As with all medication there can be , they are very minimal. Some people can report a rash or itchy dryness of the scalp. Normally the foam is less of an irritant on the skin. Therefore if you are using the lotion and suffer from these side affects then try switching to the foam. These symptoms should revert back if the medication is stopped.
Like Propecia this also prevents further hair loss by stabilising things. The thinning hair shaft can be thickened up and even if you do not have more hair. Regaine and Propecia can give you the appearance of more hair due to the fact that your existing hair shafts are thicker.