Oxandrolone is used with a diet and exercise program to cause weight gain in patients who have lost too much weight due to surgery, injury, or long lasting infections, or who are very underweight for unknown reasons. Oxandrolone is also used to treat bone pain in patients with osteoporosis (a condition in which the bones become thin and weak and break easily) and to prevent certain side effects in patients who take corticosteroids (a group of medications used to treat many conditions that involve inflammation or swelling of part of the body for a long time. Oxandrolone is in a class of medications called anabolic steroids. It works by increasing the amount of protein made by the body. This protein is used to build more muscle and increase body weight.