Metronidazole Elimination is Preserved in the Elderly

Abstract

1 The disposition of metronidazole and its major metabolites was compared in 11 subjects aged 86 ± 6 years and 8 aged 30 ± 6 years. 2 The plasma clearance of metronidazole was 1.20 ± 0.53 and 1.25 ± 0.22 ml min-1 kg -1, the volume of distribution 0.77 ± 0.27 and 0.77 ± 0.09 1 kg -1 and the half-life 7.8 ± 1.9 and 7.2 ± 0.9 h in elderly and young subjects, respectively (P > 0.05). 3 The area under the plasma concentration-time curve of the hydroxy metabolite was 32 ± 14 and 21 ± 3 mM min-1 (P < 0.05) whereas its half-life was 21 ± 14 and 12 ± 2 h (P < 0.05) in the elderly and young subjects, respectively. 4 The recovery in the urine of metronidazole and its metabolites was 42 ± 21% and 87 ± 6% of dose in elderly and young subjects, respectively (P < 0.05). With this reservation the only elimination pathways of metronidazole affected by old age were the renal excretion of unchanged compound and the hydroxy metabolite. 5 It is concluded that the ability to eliminate metronidazole is preserved in old age and that age-related dose adjustments are not necessary.