DMPA and Bone Health

Depot medroxyprogesterone acetate (DMPA) lowers bone mineral density slightly during use. The loss follows ovulation suppression and low circulating oestradiol, is largest in the first 1 to 2 years and then slows, and is at least partly regained after stopping. It may raise the risk of osteoporosis and possibly fractures after menopause, but no age limit and no time limit on use are set.

Products. Medroxyprogesterone acetate 150 mg deep intramuscular every 13 weeks, or 104 mg subcutaneous every 13 weeks.

Mechanism of bone effect. Gonadotrophin suppression lowers ovarian oestradiol production, which reduces bone formation relative to resorption.

Evidence. Evidence for fractures is limited and mixed. The clinical weight rests on the contraceptive benefits, which usually outweigh the bone concern, including the high risk of pregnancy and maternal morbidity when no effective method is used.

Return of bone density. Density rises again after stopping. Recovery is more complete in adults than in adolescents still gaining peak bone mass.

Eligibility categories. Under 18 years and over 45 years: category 2. BMI of 30 or more: category 1. No age limit and no limit on duration of use.

Assessment. Take a bone-risk history before and during use:

• Previous fragility fracture, or family history of hip fracture.
• Long-term systemic glucocorticoids.
• Malabsorption, chronic liver or kidney disease, hyperthyroidism, hyperparathyroidism.
• Eating disorder, very low body weight, amenorrhoea from other causes.
• Heavy smoking and alcohol use.
• Tenofovir-based antiretroviral therapy, which also lowers bone density.
• Low calcium intake, vitamin D deficiency, little weight-bearing activity.

Investigations. Bone density scanning is not required before or during use. Consider it only when several independent risk factors are present or a fragility fracture has occurred.

Choice of method. Where bone risk is high and other methods are acceptable, prefer an implant, an intrauterine device or a pill. Where no other method is acceptable, use DMPA with measures to protect bone.

Counselling. Obtain informed consent and explain the slight bone loss, that it is largely regained after stopping, that fracture risk after menopause is uncertain, and that stopping early for this reason is not needed. Adolescents under 18 years give assent. Condoms are advised for infection protection.

Regimen. Medroxyprogesterone acetate 150 mg intramuscular, or 104 mg subcutaneous, every 13 weeks; up to 4 weeks late without backup; backup for 7 days if later. Start within 7 days of menses without backup; later starts need backup for 7 days. Breastfeeding women start from 6 weeks. No dose change for body weight, liver disease or enzyme inducers.

Bone protection.

• Dietary calcium intake of about 1000 mg a day for adults (about 1300 mg for adolescents), from food first and supplements only to make up a gap.
• Vitamin D sufficiency through sunlight exposure, diet or supplementation as needed.
• Weight-bearing exercise.
• Stop smoking and limit alcohol.

Monitoring. Review at least once a year for bone-risk factors, weight, blood pressure and wishes. Ask about fractures and height loss.

Stopping and switching. Stop when the patient chooses or when a better-suited method is available. For patients over 45 years, review the need for contraception regularly. DMPA and norethisterone enanthate are not interchangeable except by switching at the due date.

Special groups.

• Adolescents: bone mass is still accumulating, so use is category 2; offer other methods first when acceptable, but do not withhold DMPA.
• Perimenopause: category 2 over 45 years; stopping is considered once contraception is no longer needed.
• HIV with tenofovir: bone loss may add up; review risk and consider other methods.
• Breastfeeding: bone density also falls during lactation; start from 6 weeks.

Expected effects. Slight bone density reduction, bleeding changes, amenorrhoea, weight change, headache, mood change.

Fragility fracture or very low density. Stop DMPA and offer another method. Assess for secondary causes (calcium and vitamin D status, thyroid, parathyroid, renal function, glucocorticoids, malabsorption) and refer for specialist assessment and bone-protective treatment as needed.

Heavy or prolonged bleeding. Exclude gynaecological disease and pregnancy. Ibuprofen 400 to 800 mg orally three times daily with food for 7 to 14 days (maximum 2400 mg in 24 hours; avoid in peptic ulcer, renal impairment, severe liver disease, NSAID-sensitive asthma), or a combined oral contraceptive, one active tablet daily for 1 to 3 cycles, if oestrogen is not contraindicated and not breastfeeding under 6 months.

Red flags. Bone pain, new back pain, height loss, any low-trauma fracture, severe lower abdominal pain.

Referral and escalation. Refer low-trauma fractures and suspected secondary osteoporosis to a specialist, and refer patients who want to stay on DMPA with several risk factors for individual review.