Pharmacokinetics of levormeloxifene in young versus elderly postmenopausal women

Physiologic changes of aging may affect processes of drug absorption and distribution, in some cases necessitating age-dependent dose adjustment.

The possibility of age dependence in the pharmacokinetic behavior and tolerability of levormeloxifene was investigated in a single-center, open-label study.

The study comprised 2 groups of healthy postmenopausal women: group A included younger subjects (50-60 years) and group B included elderly subjects (> or = 66 years). All subjects received a single 40-mg tablet of levormeloxifene base. Blood samples were collected immediately before drug intake and at several points after administration, through day 34. Peak plasma concentration, time to maximum plasma concentration, area under the plasma concentration-time curves from zero to the last quantifiable value and to infinity, and terminal half-life were calculated for levormeloxifene and compared between age groups.

Of 29 subjects enrolled, 28 (15 group A, 13 group B) completed the study. The ages of the women in group A ranged from 50 to 58 years and in group B from 66 to 79 years. No serious adverse events were reported. Ten subjects experienced 17 adverse events, of which 2 (abdominal pain and vaginal hemorrhage) were judged to be possibly related to study drug. There was no noticeable difference between age groups in the frequency of adverse events or laboratory abnormalities. The plasma concentration-time curves of levormeloxifene were indistinguishable between age groups up to 48 hours after dosing. From 72 hours onward, the mean plasma concentration-time curve was approximately 20% higher and the area under the curve was approximately 19% greater in the older subjects compared with the younger subjects. However, no statistically significant differences were observed between groups in any of the pharmacokinetic parameters, except for the elimination rate constant. The difference in mean elimination half-life was 25 hours (group A, 126 hours; group B, 151 hours).

The findings suggest that it is not necessary to adjust the dose of levormeloxifene on the basis of age in postmenopausal women. However, these results need confirmation in a multiple-dose setting under steady-state conditions--that is, as the drug is intended to be used clinically.