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 pregnane‐diol‐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.