What is the initial dosing regimen for Depo-provera (medroxyprogesterone acetate)?

Initial Dosing Regimen for Depo-Provera (Medroxyprogesterone Acetate)

The recommended initial dose for Depo-Provera is 150 mg administered by deep intramuscular (IM) injection in the gluteal or deltoid muscle every 3 months (13 weeks). 1

Administration Timing

The timing of the first injection is critical for ensuring contraceptive effectiveness:

• First injection should be given ONLY during the first 5 days of a normal menstrual period or within the first 5 days post-partum 1
• For post-partum mothers who exclusively breastfeed, administer after the sixth post-partum week 1
• When switching from other contraceptive methods (e.g., oral contraceptives), give the first injection on the day after the last active tablet or at the latest, on the day following the final inactive tablet 1

Administration Technique

• The 1 mL vial should be vigorously shaken just before use to ensure a uniform suspension 1
• Administer using strict aseptic technique 1
• Body habitus should be assessed prior to each injection to determine if a longer needle is necessary, particularly for gluteal IM injection, to avoid inadvertent subcutaneous injection 1
• Rotate injection sites with every injection 1

Dosing Considerations

• Dosage does not need to be adjusted for body weight 1
• The subcutaneous formulation (104 mg/0.65 mL) is an alternative option, which delivers a 30% lower total dose while still suppressing ovulation for more than 13 weeks 2
• Efficacy depends on adherence to the dosage schedule of administration 1
• If the time interval between injections exceeds 13 weeks, pregnancy should be ruled out before administering the next dose 1

Important Precautions

• Not recommended for long-term use (longer than 2 years) due to potential bone mineral density loss 1
• Contraindicated in patients with:
  • Active thrombophlebitis or thromboembolic disorders
  • Known or suspected breast malignancy
  • Hypersensitivity to medroxyprogesterone acetate
  • Significant liver disease
  • Undiagnosed vaginal bleeding 1

Patient Counseling

• Inform patients about expected menstrual changes (irregularities progressing to amenorrhea in 57% of women after one year) 3
• Discuss potential side effects including weight gain, headache, nervousness, abdominal pain, dizziness, and asthenia 3
• Emphasize the importance of returning for injections on schedule (every 13 weeks) to maintain contraceptive effectiveness 4
• Advise on calcium (1300 mg) and vitamin D (600 IU) supplementation, regular weight-bearing exercise, and smoking cessation to maintain bone health 4

Clinical Pearls

• Depo-Provera has a very low failure rate (<1%) when administered correctly 4, 3
• MPA is detectable in serum within 30 minutes after injection, with concentrations plateauing at about 1.0 ng/mL for about three months 5
• Median time for return to ovulation after discontinuation is approximately 30 weeks, with a 97.4% cumulative rate of return to ovulation at 12 months 2
• Pre-use counseling about menstrual changes is essential to minimize discontinuation rates 6

Remember that Depo-Provera provides contraception but not protection against sexually transmitted infections. Proper administration timing and technique are crucial for maintaining its high contraceptive efficacy.