Obesity is associated with comorbidities of which pharmacological treatment is needed. Physiological changes associated with
obesity may influence the pharmacokinetics of drugs, but the effect of
body weight on
drug metabolism capacity remains uncertain. The aim of this study was to investigate ex vivo activities of hepatic
drug metabolizing CYP
enzymes in patients covering a wide range of
body weight. Liver biopsies from 36 individuals with a body mass index (BMI) ranging from 18 to 63 kg/m2 were obtained. Individual hepatic microsomes were prepared and activities of
CYP3A,
CYP2B6,
CYP2C8,
CYP2D6,
CYP2C9,
CYP2C19 and
CYP1A2 were determined. The unbound intrinsic clearance (CLint,u) values for
CYP3A correlated negatively with
body weight (r = -0.43, p < 0.01), waist circumference (r = -0.47, p < 0.01), hip circumference (r = -0.51, p < 0.01), fat percent (r = -0.41, p < 0.05), fat mass (r = -0.48, p < 0.01) and BMI (r = -0.46, p < 0.01). Linear regression analysis showed that CLint,u values for
CYP3A decreased with 5% with each 10% increase in
body weight (r2 = 0.12, β = -0.558, p < 0.05). There were no correlations between
body weight measures and CLint,u values for the other CYP
enzymes investigated. These results indicate reduced hepatic metabolizing capacity of
CYP3A substrates in patients with increasing
body weight.