The effects of degree of hepatic or renal impairment on the pharmacokinetics of exemestane in postmenopausal women

Two studies were conducted to compare the pharmacokinetics and tolerability of exemestane in postmenopausal subjects with various degrees of impairment of hepatic or renal function with those in healthy postmenopausal subjects.

All subjects were postmenopausal females. In study 1, nine subjects had normal hepatic function (Child-Pugh grade A), and nine had moderately (grade B) and eight severely (grade C) impaired hepatic function. In study 2, six subjects had normal renal function, and six moderately (creatinine clearance, CrCL, 30–60 ml/min per 1.73 m²) and seven severely (CrCL <29 ml/min per 1.73 m²) impaired renal function. Each subject took a single oral dose of 25 mg exemestane. Samples of plasma (to 168 h after dosing) and urine (to 72 h in study 1, or 96 h in study 2) were taken for pharmacokinetic analysis. Safety and tolerability were assessed by monitoring vital signs, laboratory safety tests, ECG and adverse events.

Exposure to exemestane was increased two- to threefold in patients with hepatic impairment. Thus, the geometric mean AUC_0–∞ values were 41.71 (90% CI 32.2 to 54.0), 99.02 (76.5 to 128.2) and 118.59 ng·h/ml (90.2 to 156.0) in healthy subjects, and in patients with moderate and severe hepatic impairment, respectively (P<0.01). C_max also increased twofold. Compared with healthy subjects, patients with hepatic impairment had lower apparent oral clearance and apparent volume of distribution of exemestane. Renal impairment was also associated with two- to threefold increases in AUC_0–∞: 34.64 (90% CI 23.9 to 50.2), 94.10 (64.9 to 136.4) and 65.52 ng·h/ml (46.5 to 92.4) in healthy subjects, and in patients with moderate and severe hepatic impairment, respectively (P<0.05). C_max did not change significantly. Apparent oral clearance was directly correlated with CrCL (r ²=0.43). Exemestane was tolerated well, with no safety concerns.

Oral clearance of exemestane was reduced in the presence of significant hepatic or renal disease. However, in view of the relatively large safety margin and the mild nature of the side effects of exemestane, the therapeutic implications of these changes in pharmacokinetics are considered minor and of no clinical significance.