What is the effectiveness and safety of the Depo-Provera (medroxyprogesterone acetate) birth control shot?

Effectiveness and Safety of Depo-Provera Birth Control Shot

Depo-Provera (medroxyprogesterone acetate) is an effective contraceptive with a typical use failure rate of 6% and perfect use failure rate of less than 1%, but users should be aware of potential side effects including menstrual irregularities, bone mineral density loss, and weight gain. 1

Effectiveness

• Highly effective contraceptive method with:
  • Perfect use failure rate: less than 1%
  • Typical use failure rate: approximately 6% 2, 1, 3
• Effectiveness depends on receiving injections on schedule every 13 weeks (3 months) 1
• More effective than barrier methods, fertility awareness methods, and oral contraceptives, but slightly less effective than IUDs or implants 2

Administration Options

• Standard intramuscular (IM) injection: 150 mg every 13 weeks
• Subcutaneous (SC) injection: 104 mg every 13 weeks
  • Self-administration option now available for subcutaneous form 2, 1
  • Self-administered DMPA-SC has shown higher continuation rates compared to provider-administered DMPA 2

Mechanism of Action

• Inhibits ovulation by suppressing the mid-cycle LH surge
• Thickens cervical mucus, making it difficult for sperm to penetrate
• Creates an atrophic endometrium unsuitable for implantation 4
• Detectable in serum within 30 minutes after injection
• Serum concentrations plateau at approximately 1.0 ng/mL for about three months 4

Common Side Effects

Menstrual Changes

• Nearly all users experience menstrual irregularities initially 1
• Patterns typically include:
  • Irregular spotting or bleeding
  • Prolonged bleeding episodes
  • Amenorrhea (absence of periods) in many long-term users 5, 6
• Thorough pre-use counseling about expected menstrual changes significantly reduces discontinuation rates 1, 6

Weight Changes

• Weight gain is a common side effect 1
• Weight gain at 6 months may predict future excessive weight gain 1
• Consider alternative methods for patients with obesity or at risk for weight-related complications 1

Bone Health Concerns

• Associated with loss of bone mineral density (BMD) 1, 3
• FDA recommends:
  • Adequate calcium (1300 mg/day) and vitamin D (600 IU/day) intake
  • Regular weight-bearing exercise
  • Smoking cessation to support bone health 1

Other Side Effects

• Mood changes
• Headaches
• Decreased libido
• Breast tenderness 6

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 1
• Delayed return to fertility is an important counseling point for women planning future pregnancies 4

Important Considerations

• Does not protect against sexually transmitted infections (STIs) 1, 3
• Self-administered subcutaneous DMPA should be made available as an additional approach to deliver injectable contraception 2
• Appropriate for adolescents with proper counseling about side effects and bone health considerations 1
• Safe for use in women with HIV with no significant interactions with antiretroviral medications 1
• Safe in women with rheumatic and musculoskeletal diseases 2

Common Pitfalls to Avoid

1. Missing the injection window (must be given within 13-15 weeks)
2. Inadequate counseling about menstrual changes leading to discontinuation
3. Overlooking bone health considerations, especially in adolescents
4. Forgetting that DMPA provides no STI protection
5. Ignoring potential weight gain and its implications

Depo-Provera offers a convenient, highly effective contraceptive option that doesn't require daily attention. The subcutaneous self-administration option may improve access and increase reproductive autonomy. However, thorough counseling about expected side effects, particularly menstrual changes and potential weight gain, is essential for patient satisfaction and continuation.