There are lots of ways to promote hair regrowth, both natural and prescription. A quick internet search will show you that lemon juice and egg whites are a proven method to moisturize the scalp and improve hair regrowth and prevent loss.

If you are looking for a prescription based solution, there is rogaine, propecia, etc. etc. I did a quick query and found this website that has a bunch of information concerning women’s hair loss and how it can be prevented:
http://www.hairlossspecialists.com/forwomen.cfm

My wife actually used them when she was having some hair loss problems of her own (thankfully, it turned out to be stress related and now she is fine.)

Hope I could help.

Check with your doctor or pharmacist if the side effect is reversible after discontinuation of the medication.
If not OR if it is an on-going medication you have to take continuously. Then check with your doctor if minoxidil 2 to 5% local application can help. Although this medication is used primarily in male, I have seen 4% worked in a female patient.
The draw-back is that you have to keep using it. Once stopped, you hair may thin again gradually.

You can stop hair loss using many cheap and effective home remedies. Egg white, lemon juice, oil massage are other home remedies at http://www.wellnesstalk.org/hairfall.html will prevent further problems.