Age-related changes in trimethadione oxidizing capacity.

The metabolism of trimethadione (TMO) following oral administration (4 mg kg-1) has been studied in 11 young male and 11 elderly male patients. The elimination half-life (h) of TMO was 11.8 +/- 1.4 (mean +/- s.e. mean) in the young and 23.5 +/- 2.17 in the elderly (P less than 0.01). Total body clearance (1 h-1 kg-1) was 41.4 +/- 2.8 in the young and 29.0 +/- 2.4 in the elderly (P less than 0.01). The apparent volume of distribution (1 kg-1) was 0.67 +/- 0.03 in the young and 0.65 +/- 0.04 in the elderly. Serum dimethadione (DMO)/TMO ratios at 4 h were 0.65 +/- 0.03 in the young and 0.46 +/- 0.03 in the elderly (P less than 0.01). These results suggest that N-demethylation of TMO is inversely related to age.