Alendronic Acid for Antipsychotic-Related Osteopenia

Ms. A was a 58-year-old woman with paranoid schizophrenia. She had received trifluoperazine, 10 mg/day, for 2 years, followed by a depot injection of haloperidol decanoate, 125 mg every 2 weeks, for the past 12 years. After starting the haloperidol depot, she was amenorrheic for 18 months. Her periods were then regular until menopause, which occurred 7 years before she was seen. She was taking procyclidine, 5 mg/day, for mild extrapyramidal symptoms and had been stable since her only hospital admission 12 years ago.

Our medication review service gave Ms. A a systematic evaluation of symptoms, side effects, and physical health. The assessment showed a mildly elevated prolactin level (505 mIU/ml, upper limit of normal=450 mIU/liter). Her gonadal hormone levels were consistent with her postmenopausal status (estradiol, 44 pmol/liter; follicle-stimulating hormone, 54 IU/liter; luteinizing hormone, 30.9 IU/liter; progesterone, 1.08 nmol/liter).

In view of her hyperprolactinemia, Ms. A’s bone mineral density was evaluated with a dual X-ray absorptiometry scan of her lumbar spine and hip. Her spine and hip t scores were –2.02 and –1.74, respectively, both indicating osteopenia and an increased risk of fracture (3). Her age-corrected scores were low, at –0.67 (spine) and –0.84 (hip), compared to normal values of 0. She was uniparous and had never smoked or breast-fed. Her diet typically included 500 mg/day of calcium. She performed 140 minutes of weight-bearing exercise per week. There was no personal or maternal history of bone fracture or medical conditions.

Ms. A did not wish to change antipsychotic treatment, citing its convenience. She began taking alendronic acid, 5 mg/day, to treat her osteopenia. A dual X-ray absorptiometry scan at 1 year showed that her spine and hip t scores had improved by 7% and 9% to –1.87 and –1.58, respectively. Her prolactin level remained mildly elevated.