Ovulation suppression following subcutaneous administration of depot medroxyprogesterone acetate

Objectives

To characterize the relationship between serum medroxyprogesterone acetate (MPA) concentrations and ovulation suppression, and to estimate the risk of ovulation for investigational subcutaneous regimens of Depo-Provera CI (Depo-Provera) and Depo-subQ Provera 104 (Depo-subQ).

Study Design

We performed a secondary analysis of 2 studies that assessed the pharmacokinetics and pharmacodynamics of MPA when Depo-Provera is administered subcutaneously rather than by the labeled intramuscular route. Each woman received a single 45 mg to 300 mg subcutaneous injection of Depo-Provera, a single 104 mg subcutaneous injection of Depo-subQ, or 2 injections of Depo-subQ at 3-month intervals. We used an elevation of serum progesterone ≥4.7 ng/mL as a surrogate for ovulation and non-parametric statistical methods to assess pharmacokinetic and pharmacodynamic relationships.

Results

This analysis included 101 women with body mass index (BMI) 18 to 34 kg/m². Return of ovulation occurred at a median MPA concentration of 0.07 ng/mL (95% CI: 0.06–0.08) and the 90th percentile was 0.10 ng/mL (95% CI: 0.09–0.14). Neither age, race, nor BMI significantly influenced this relationship. The estimated probabilities of ovulation within 4 months of a 104 mg subcutaneous injection and within 7 months of a 150 mg subcutaneous injection (6 plus a 1-month grace) were each below 2.2%.

Conclusions

The typical MPA concentration associated with loss of ovulation suppression is substantially less than the commonly cited threshold of 0.2 ng/mL. Based on our results, MPA levels would rarely be low enough to permit ovulation if the Depo-subQ reinjection interval were extended to four months or if 150 mg Depo-Provera were injected subcutaneously every 6 months.

Implications

Extending the three-month Depo-subQ reinjection interval by one month would result in a 25% reduction in yearly MPA exposure, with little risk of pregnancy. Off-label subcutaneous administration of 150 mg Depo-Provera every 6 months would be a highly effective repurposing of an excellent product, with a similar reduction in cumulative exposure.