No more than two years...that's what the FDA suggests now to women using Depo-prevera for birth control. Remember, that's the contraception by injection.
The FDA says it's safe, but women who depend on that for more than two years should be aware of a serious side effect. The so-called "black box" warning will soon be added to labels highlighting that prolonged use may result in the loss of bone density. Beyond two years, the longer the drug is used, the greater the risk of loss of bone density and the condition may not be reversible even if the drug is discontinued.