Age and CYP3A4 and CYP2A6 activities marked by the metabolism of lignocaine and coumarin in man.

The effect of age on human liver drug-metabolizing ability was investigated by using probe drugs, metabolized by specific isozymes in liver, as an index. Formation of monoethylglycinexylide (MEGX) after i.v. infusion of lignocaine (1 mg/kg), metabolized by CYP3A4, and excretion of 7-hydroxycoumarin (7-OHC) after oral coumarin (5 mg) administration, hydroxylated by CYP2A6, were investigated in healthy young (< 25 years) and elderly (> 65 years) women and men (n = 10 in each group). MEGX content in young subjects (men 57.8 +/- 11.3 and women 52.9 +/- 13.1 ng/ml) did not diverge significantly but was reduced in elderly subjects (men 43.57 +/- 15.8 and women 29.2 +/- 13.6 ng/ml, p < 0.05 and 0.01, respectively). 7-OHC excretion at 2 h averaged 68.1 +/- 13.1 per cent (men) and 65.0 +/- 18.3 per cent (women) of the dose given in young subjects and was delayed in elderly persons (men 46.5 +/- 16.3 per cent and women 44.8 +/- 18.3 percent, p < 0.01 and 0.05, respectively). The change in probe drug metabolism was related to age (MEGX, r = -0.473 (men) and -0.682 (women) and 7-OHC; r = -0.690 (men) and -0.565 (women)). MEGX formation was reduced by 0.92 microgram/L per year and 7-OHC excretion by 0.85 per cent per year. The results indicate a decrease of CYP3A4 and CYP2A6 metabolic activities with age.