A study to evaluate serum and urinary hormone levels following short and long term administration of two regimens of progesterone cream in postmenopausal women

OBJECTIVE: To determine the pharmacokinetics of a progesterone cream following short and long term dermal administration. DESIGN: Single-centre, randomised, multiple-dose, open-label study. SETTING: Reproductive Medicine Trust, London. POPULATION: Twenty-four healthy postmenopausal women aged between 40 and 65 years were recruited through an advertisement in a local newspaper. METHODS: The women were randomly allocated to progesterone cream 40 mg daily or 20 mg, twice daily, for 42 days. MAIN OUTCOME MEASURES: The concentration of progesterone in the serum was measured on days 1 and 42 before the morning dose, and at 2, 4, 6, 12 and 24 hours after the morning dose. Serum follicle stimulating hormone, oestradiol, testosterone and urinary pregnanediol-3-glucuronide were also measured on days 1 and 42. RESULTS: Three subjects dropped out before using the cream and two more dropped out after the first treatment leaving a reportable sample of 19 women. There was a rise in the mean progesterone concentration at each sampling time between days 1 and 42. There was evidence of a rise in pregnanediol-3-glucuronide over the course of the study. There was no change in follicle stimulating hormone, oestradiol or testosterone. There was no difference between the two regimens. CONCLUSIONS: Transdermal progesterone (40 mg) per day for 42 days causes a small increase in serum progesterone concentration, although there is wide variation. Whether such levels are of clinical benefit remains to be seen.