Pharmacokinetics of quinine in young and elderly subjects.

The effect of age on the pharmacokinetics of quinine was investigated by comparing its kinetic behaviour in 12 young healthy adults and 8 healthy elderly subjects after a single 600 mg oral dose of quinine sulphate. Peak plasma quinine concentration and the time of peak concentration were similar in the young and elderly subjects. The mean oral clearance of quinine was found to be significantly decreased in the elderly (P less than 0.05, 0.062 litre/h/kg vs 0.084 litre/h/kg) as compared to the young. This was accompanied by a significant increase in the mean elimination half-life of quinine in the elderly group (18.4 +/- 5.7 [standard deviation] h vs 10.5 +/- 1.6 h, P less than 0.05). There was no significant difference in the renal clearance of quinine between the young and the elderly (P greater than 0.05). However, elderly subjects excreted 16.6 +/- 3.7% of the dose as unchanged quinine in the urine and this was significantly greater (P less than 0.005) than the amount excreted by the young (11.2 +/- 2.5%). The results of this study indicate that the elimination processes for quinine are impaired in normal elderly subjects. The clinical significance of these findings is unknown, but they indicate the need for caution in the administration of quinine to elderly patients.