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Teenagers, Bone Loss, and Long-term Depot Medroxyprogesterone Acetate Use (24 Months)
Abstract & Commentary
By Alison Edelman, MD, MPH, Assistant Professor, Assistant Director of the Family Planning Fellowship, Department of Obstetrics & Gynecology, Oregon Health & Science University, Portland, is Associate Editor for OB/GYN Clinical Alert.
Dr. Edelman reports no financial relationship to this field of study.
Synopsis: Although bone loss does occur in adolescent depot medroxyprogesterone acetate (DMPA) users, this loss slows after one year and even with continued use, bone density appears to be maintained in the normal range.
Source: Cromer BA, et al. Bone mineral density in adolescent females using injectable or oral contraceptives: A 24-month prospective study. Fertil Steril 2008;90:2060-2067.
Cromer et al performed a 24-month observational, prospective cohort study of adolescents in the Midwest using depot medroxyprogesterone acetate (DMPA), oral contraceptives (OCs), or nothing. DEXA scans were performed at baseline and 6-month intervals. Over 24 months, DMPA users lost a small percentage of bone mineral density (spine = -1.5%, femoral neck = -5.2%), whereas OC users and the control group gained (OC: spine = +4.2%, femoral neck = +3%; control: spine = +6.3%, femoral neck = +3.8%). The majority of the bone loss in the DMPA group occurred in the first 12 months of use (1.4%) and then slowed to (0.1%) with continued use over the next 12 months. Even with loss of bone mineral density in the DMPA group, values remained in the normal range and no participant met the criteria for osteopenia.
Depot medroxyprogesterone acetate or DMPA (150 mg intramuscularly every 12 weeks) is a highly effective, reversible, long-acting contraceptive method that requires minimal effort for the user to be compliant. In addition, its invisibility (injectable delivery system with no necessary home-based paraphernalia) offers privacy to the user — a very important quality in a contraceptive method for many teens. Other advantages of DMPA include many noncontraceptive benefits (reduction of menstrual symptoms such as excessive bleeding and dysmenorrhea, and improvement of anemia) and, as a progestin-only method, it can be used safely in women with contraindications to estrogen.1,2
Unfortunately, in November 2004, the FDA issued a black box warning for DMPA, which unnecessarily scared many providers and users away from this very reliable and useful method. This warning stated that prolonged use of DMPA may result in significant loss of bone mineral density, the loss is proportional to the amount of time on DMPA, and the bone mineral density decrease may not be completely reversible. The warning went on to state that women should use DMPA for more than 2 years only if other contraceptive methods are "inadequate."3
We fully acknowledge that DMPA affects bone mineral density, but the warning overstated many of the concerns, did not specifically address unique populations like adolescents, and did not offer any practical clinical advice on how to manage patients. In addition, the FDA did not address the limitations of DEXA scanning in premenopausal women (DEXA scanning can document changes in bone mineral density but this has no relationship to fracture risk).
In reviewing research regarding DMPA use in teens, it is reassuring to note that the recovery of bone density after DMPA use appears to be no different than bone density recovery following breastfeeding.4,5
I found the recent publication by Cromer et al reassuring as well.1 The original FDA warning stated that the bone loss was proportional to the amount of time on DMPA; however, Cromer et al found that the effect on bone loss significantly slowed during a second year of use. It is still unknown if DMPA use in teens affects peak bone mass, but this needs to be offset by the risk for pregnancy and pregnancy's effect not only on bone but also a teen's overall future. Even taking a study population where contraceptive compliance is often higher, Cromer et al had a 15% pregnancy rate in their OC users and none in their DMPA users.
For a more balanced, evidence-based clinical approach to DMPA use in teens, you can go to the World Health Organization's statement on DMPA use at www.who.int/reproductive-health.6