DMPA Cannot Be Given Monthly
No, DMPA (depot medroxyprogesterone acetate) must be administered every 3 months (13 weeks), not monthly, as this is the only dosing interval that provides effective contraceptive coverage and appropriate hormonal suppression. 1
Standard Dosing Interval
- The FDA-approved and guideline-recommended regimen is 150 mg intramuscularly or 104 mg subcutaneously every 13 weeks (3 months). 2, 3
- This quarterly schedule is based on the pharmacokinetics of DMPA, which maintains therapeutic serum concentrations for approximately 3 months before declining. 3, 4
- After a single 150 mg IM injection, medroxyprogesterone acetate concentrations plateau at approximately 1.0 ng/mL for about three months, then gradually decline. 4
Allowable Timing Flexibility
- Injections may be given up to 2 weeks late (within 15 weeks of the prior dose) without requiring additional contraceptive protection. 1
- Many clinicians schedule appointments every 11-12 weeks to provide a buffer for missed appointments, but this is still within the 3-month framework, not monthly dosing. 2, 5
Why Monthly Dosing Is Not Appropriate
- The mechanism of action depends on sustained release from the intramuscular or subcutaneous depot, with ovulation inhibited for at least 14 weeks after a 150 mg dose. 6
- Serum MPA levels remain detectable for 120-200 days following a single injection, with an apparent half-life of approximately 50 days. 3, 4
- Monthly administration would result in drug accumulation, unpredictable hormone levels, and has no established safety or efficacy data. 3
For Endometriosis Treatment
- Even when DMPA-SC 104 mg is used for endometriosis-associated pain (not just contraception), the dosing remains every 3 months for 6 months, not monthly. 7
- This quarterly schedule was equivalent to leuprolide acetate in reducing endometriosis symptoms while causing less bone mineral density loss. 7
Common Pitfall to Avoid
Do not confuse DMPA with other hormonal contraceptives that have monthly formulations (such as monthly combined injectable contraceptives available in some countries). DMPA is specifically formulated as a long-acting depot preparation requiring quarterly administration, and altering this schedule compromises both safety and efficacy. 1, 3, 6