Pharmacokinetics of depot medroxyprogesterone acetate contraception.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing pharmacokinetic data without systematic methodology
What was done
Narrative review describing the pharmacokinetics, endocrine effects, mechanisms of action, and tissue responses associated with 150 mg intramuscular injections of depot medroxyprogesterone acetate (DMPA) for long-term contraception.
What was found
Medroxyprogesterone acetate (MPA) appears in serum within 30 minutes following a 150 mg injection, plateaus at approximately 1.0 ng/mL for about 3 months, and remains detectable for up to 9 months in some women. The midcycle luteinizing hormone surge is inhibited, keeping serum progesterone under 0.4 ng/mL; ovulation resumes when MPA falls below 0.1 ng/mL. Serum estradiol averages approximately 50 pg/mL initially and rises after 4 months once MPA drops below 0.5 ng/mL. Long-term users maintain mean estradiol levels of about 40 pg/mL (range 10 to 92 pg/mL). The endometrium becomes atrophic with decidualized stroma, and cervical mucus remains thick and viscid.
Why it matters
Provides reference pharmacokinetic and hormonal thresholds that explain the 3-month dosing interval of DMPA and the physiological mechanism behind delayed return of fertility after discontinuation.
Limits
As a narrative review, it lacks a systematic search strategy, aggregate sample size, inclusion criteria, or critical appraisal of the cited evidence. Specific confidence intervals and variance estimates are not provided in the abstract.
Cited by
- supports A single intramuscular injection of Depo-Provera can prevent ovulation for up to 18 months.