Bone loss with Depot shots slows after 2 years

By Will Boggs, MD

NEW YORK (Reuters Health) - Contrary to its "black box" warning, using depot medroxyprogesterone acetate (DMPA) contraceptives for longer than 2 years does not substantially increase the risk of osteoporosis, according to a study.

"Bone loss does not go on indefinitely, despite continued DMPA use," Dr. M. Kathleen Clark from the University of Iowa, Iowa City, told Reuters Health. "In fact, our data suggest that there is no additional spine loss and very little additional hip bone mineral density (BMD) loss beyond 2 years."

DMPA contraceptives are given by monthly injections, and are often referred to by one brand name, Depo Provera.

Clark and colleagues compared BMD changes during 48 months between 178 first-time DMPA users (during use and after discontinuation) and 145 women not using hormonal contraception.

Over 48 months of DMPA use, mean hip BMD declined by 7.7 percent and mean spine BMD declined by 6.4 percent, the authors report. This compares with a decline of 1.6 percent in mean hip BMD and an increase of 0.5 percent in mean spine BMD among controls.

Three quarters of the hip BMD loss and 90 percent of the spine BMD loss occurred during the first 24 months of DMPA use. By 48 months after starting DMPA, annual BMD losses had declined to only 0.6 percent at the hip and actually increased 0.4 percent at the spine during the 4th year.

BMD at the hip and spine recovered linearly after discontinuation of DMPA, the researchers note, with recovery slower at the hip than at the spine. BMD still remained lower than that of controls.

"Based on our findings, the recommendation to have bone density monitored with long-term use probably is not warranted," the authors conclude, "since most BMD is lost within the first two years, and that loss is generally not sufficient to pose an immediate risk for fracture."

SOURCE: Fertility and Sterility November 2006.