Comparative bioavailability of orally and vaginally administered progesterone
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T R Norman1, C A Morse, L Dennerstein
1Department of Psychiatry, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
Objective:
To study the pharmacokinetics of progesterone (P) in healthy premenopausal female volunteers to compare the bioavailability of orally or vaginally administered hormone.
Design:
Subjects were randomly allocated to receive either oral P or a vaginal pessary then crossed over to the alternate preparation 1 month later.
Setting:
The study was conducted in outpatient setting.
Subjects:
All subjects were healthy, normal female volunteers who underwent a physical and gynecological examination before the study. None were using oral contraceptives. Ten subjects (mean age 32.6 +/- 7.3 years) entered the study and all completed it.
Interventions:
Progesterone was administered as 200 mg of micronized hormone or as a pessary containing 400 mg.
Main Outcome Measure:
Plasma levels of P were measured by radioimmunoassay to test the apriori hypothesis of similar bioavailability.
Results:
Peak plasma P concentrations attained within 4 hours after oral administration ranged from 8.5 to 70.6 ng/mL, whereas after vaginal administration the peak levels were attained within 8 hours and ranged from 4.4 to 181.1 ng/mL. Considerable interindividual variation was noted. Area under the plasma concentration-time curve for the two formulations was not significantly different (F = 1.09; P greater than 0.1; ANOVA).
Conclusions:
The two formulations had similar bioavailability.