Pharmacokinetics of natural progesterone administered in the form of a vaginal tablet

Our study was conducted to assess the pharmacokinetics of natural progester one administered in the novel formula of an effervescent vaginal tablet. Fi fty post-menopausal women, with a median age of 43.5 years (range 28-55), v olunteered to participate in the research. All women discontinued their hor monal replacement therapy 1 month prior to the study. The pharmacokinetics of 50 and 100 mg of progesterone administered as a vaginal tablet were eval uated. After the initial administration of 50 mg or 100 mg, a mean serum C- max of 20.43 +/- 8.01 nmol/l and 31.61 +/- 12.62 nmol/l (P < 0.0004) was re ached at a T-max of 6.1 +/- 2.63 and 6.4 +/- 3.35 h respectively. The termi nal half-life was 13.18 +/- 1.3 and 13.7 +/- 1.05 h respectively. Continuou s use of the 100-mg tablet resulted in a mean serum progesterone concentrat ion of 26.08 +/- 13.96 nmol/ 1 and 21.42 +/- 16.32 nmol/l after 14 and 30 d ays respectively. Women >40 years were found to have a significantly lower T-max compared to younger women (P = 0.02). The continuous use of vaginal p rogesterone did not influence the hormonal, liver or lipid profiles evaluat ed. Only three (6%) women suffered from mild vaginal irritation. Natural pr ogesterone given as a vaginal tablet is well tolerated, safe and an easily administered treatment. Even in a non-oestrogenized vagina the absorption w as efficient and the 100 mg dosage resulted in adequate serum progesterone concentrations.