aka Megestrol acetate aka progestin:

A synthetic progesterone (female) hormone used to treat AIDS wasting syndrome and some forms of cancer, particularily that of the breast. Megace stimulates the appetite in some people, although it can take six weeks or more before the desired effects are noticed. Weight gain is usually due to fat, not muscle. How it works is not really, as of yet, understood. For breast cancer, the daily dose is 160mg. For wasting syndrome, twice as much is taken, divided into four 80mg doses. Studies that demonstrate megace's weight-promoting abilities tend to involve larger doses, from 400-800mg.

Side effects include: