Dosage, efficacy, side effects and drug interactions

The recommended dosing interval for intramuscular DMPA (Depo-Provera®) and subcutaneous DMPA (Sayana Press®) is 13 weeks. This is outside the product licence for Depo-Provera®.

DMPA may be administered up to 14 weeks from the last injection without the need for additional contraceptive precautions. This is outside the product licence for Depo-Provera®.

Perfect use failure rate is 0.2% in the first year of use. Typical use is 6% in the first year of use.

Injectable contraceptives are long acting reversible contraceptives. Typical use failure rates are lower than failure rates for oral contraceptives. However, injectable contraceptives are less cost-effective than the implant and intrauterine methods because users are required to return more frequently.

Common side effects

• Change in menstrual pattern.
• Delay in return of fertility.
• Mean time to ovulation is 5.3 months following the preceding injection, i.e., 2 to 3 months following cessation of therapy.
• Weight gain.
• Injection site reactions - more common with subcutaneous than intramuscular injection

Less common adverse effects

• Prolonged or very heavy bleeding – history and examination must be taken to exclude gynaecology pathology (e.g., pelvic infection, miscarriahe)
• Anaphylaxis.
• Galactorrhoea
• Possible small increase in relative risk of breast and cervical cancer
• Loss of bone mineral density (see below)

Women should be informed that the efficacy of progestogen-only injectable contraception is not reduced with concurrent use of medication  (including antibiotics and liver enzyme-inducing drugs) and the injection intervals do not need to be reduced.