What is a Medroxyprogesterone Acetate (MPA) injection, also known as Depo-Provera?

Medroxyprogesterone Acetate (MPA) Injection: Depo-Provera

Medroxyprogesterone acetate (MPA) injection, commonly known as Depo-Provera, is a long-acting progestin-only injectable contraceptive administered every 13 weeks (up to 15 weeks) at a dose of 150 mg intramuscularly or 104 mg subcutaneously. 1, 2

Mechanism of Action

MPA works through multiple mechanisms to prevent pregnancy:

• Inhibits secretion of gonadotropins, preventing follicular maturation and ovulation
• Causes endometrial thinning
• Thickens cervical mucus 3, 4

These combined effects result in its high contraceptive efficacy, with:

• Typical use failure rate: approximately 6%
• Perfect use failure rate: less than 1% 1, 2

Administration

• Intramuscular injection: 150 mg deep IM injection in gluteal or deltoid muscle every 3 months (13 weeks)
• Subcutaneous injection: 104 mg every 13 weeks 2, 5

MPA is detectable in serum within 30 minutes after injection, with serum concentrations plateauing at about 1.0 ng/mL for approximately three months before gradually declining. In some women, MPA can be detected for up to 9 months after a single injection. 4

Effectiveness and Benefits

• Highly effective contraceptive method with failure rates comparable to modern copper IUDs 6
• Independent of intercourse and user's daily compliance
• Safe option for women with contraindications to estrogen-containing contraceptives
• No appreciable effects on blood pressure or thrombosis risk
• Can be used by women with focal migraines who cannot use combined hormonal contraceptives 6
• May provide protection against endometrial cancer and tubal infertility 7

Side Effects

Menstrual Changes

• Nearly all users experience menstrual irregularities initially
• Bleeding patterns typically improve over time
• Amenorrhea develops in many long-term users 1, 2
• Pre-use counseling about expected menstrual changes reduces discontinuation rates 2

Weight Changes

• Weight gain is a common side effect
• Weight gain status at 6 months is a strong predictor of future excessive weight gain 1, 2
• Alternative methods should be considered for patients at risk for weight-related complications

Bone Health Considerations

• Associated with reductions in bone mineral density (BMD)
• FDA issued a black-box warning about decreased BMD in 2004
• Substantial recovery of BMD occurs after discontinuation
• American College of Obstetricians and Gynecologists recommends:
  • Daily intake of 1300 mg calcium and 600 IU vitamin D
  • Regular weight-bearing exercise
  • Does not advise limiting DMPA use to 2 years 1, 2

Return to Fertility

• Median time for return to ovulation after discontinuation is approximately 30 weeks
• 97.4% cumulative rate of return to ovulation at 12 months
• Women with lower body weights conceive sooner than those with higher body weights 2, 3

Clinical Considerations

Follow-up

• Injections should be given within the 13-15 week timeframe to maintain contraceptive effectiveness
• Many providers schedule visits every 11-12 weeks for adolescents to allow for missed or delayed visits 1

Counseling Points

• Backup method (condoms or abstinence) should be used for at least the first week after starting
• DMPA provides no protection against STIs
• Thorough counseling about expected side effects, particularly menstrual changes and weight gain, reduces discontinuation rates 1, 2

Common Pitfalls

• Inadequate counseling about menstrual changes leading to discontinuation
• Missing the injection window
• Overlooking bone health considerations
• Forgetting STI protection needs 2

MPA injection offers a highly effective, convenient contraceptive option that doesn't require daily compliance, making it particularly suitable for those who cannot use estrogen-containing methods or who prefer a method that requires attention only every three months.