Effects of age on the pharmacokinetics of mexiletine.

Mexiletine (1-methyl-2-(2, 6-xylyloxy)ethylamine hydrochloride) is an antiarrhythmic drug eliminated primarily by hepatic metabolism. The influence of age on the plasma pharmacokinetics of mexiletine was assessed in seven young and ten elderly healthy subjects. Mexiletine (50 mg) was administered orally three times daily for 10 days. The use of low doses of mexiletine was possible owing to the development of a new fluorescence high performance liquid chromatography method with a limit of sensitivity lower than 20 ng/ml. No differences in the pharmacokinetic parameters of mexiletine related to age were observed. At steady-state plasma concentrations were 0.121 +/- 0.033 microgram-ml in the young volunteers, and 0.135 +/- 0.150 microgram/ml in the older subjects. The elimination t 1/2 was 11.4 +/- 1.78 h in the young subjects and 10.48 +/- 3.06 h in the elderly. The data provide no justification for lowering the recommended dose of mexiletine for older patients.