By John Otrompke
DENVER -- September 15, 2009 -- Depot medroxyprogesterone acetate (MPA), a long-acting contraceptive delivered by intramuscular injection, is associated with an increased risk of fractures in women aged <50 years, but the risk appears to be mitigated in those who receive oestrogen, according to a large study presented at the 31st Annual Meeting of the American Society for Bone and Mineral Research (ASBMR).
MPA is known to be associated with impaired bone mineral acquisition during adolescence and accelerated bone loss later in life, and it has been tested in populations such as developmentally disabled patients and female army recruits. More studies of this drug are needed.
MPA is thought to be involved in skeletal health concerns because it causes oestrogen depletion, said Christian Meier, MD, University Hospital, Basel, Switzerland, who presented the study on September 12. The drug is used by more than 9 million women worldwide and has a high usage rate among teenagers in Europe and the United States.
This study was conducted in 71,089 fracture cases and 274,520 control patients with data gleaned from the UK-based General Practice Research Database. Fracture patients were diagnosed between 1995 and 2007, and 4 control patients per case were matched for age, sex, general practice, calendar time, and years of historical information in the database. The population was classified by patients' previous exposure to hormonal contraceptives or postmenopausal oestrogen-replacement therapy, and results were adjusted for smoking, body mass index, and additional potential confounders.
Overall risk for current long-term use of depot MPA alone was 1.69 for patients aged <50 years and 0.82 for patients aged >=50 years. For those who used depot MPA in combination with oestrogens, the risk was decreased, the researchers said.
"There were only a few vertebral fractures in the study," Dr. Meier pointed out. "There were a [few] women treated with depot MPA who used oestrogens," he continued, referring to <5% of the study population. In addition, younger women tended to get more hand and foot fractures, whereas women aged >=50 years tended to get fractures associated with osteoporosis, such as fractures of the hip, humerus, and wrist. The fracture cases were also associated with comorbidities such as smoking or a history of asthma or epilepsy.
The researchers concluded that longer-term use of MPA in women aged <50 years increases the risk of fracture, but combination with oestrogen tends to alleviate the risk.
[Presentation title: Use of Depot Medroxyprogesterone Acetate and Fracture Risk. Abstract 1057]
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