Effects of L- and DL-carnitine on Patients with Impaired Exercise Tolerance

Abstract

We designed this study to determine whether orally administered L- and DL-carnitine can improve exercise tolerance in a group of patients with exercise intolerance. Nineteen patients with cardiac disease were randomly divided into 2 groups, an L-carnitine treatment group (n=9) and a DL-carnitine treatment group (n=10). Eight additional age-matched patients served as an untreated control group. Subjects in both carnitine treatment groups under-went cardiopulmonary exercise testing on a cycle ergometer in order to deter-mine peak exercise time, peak oxygen uptake (VO₂), lactate threshold (LT) and ventilatory threshold (VT) before and after the oral administration of 900mg/day of L- or DL-carnitine for 2 weeks. Basal values of peak exercise time, peak VO₂, LT and VT did not differ significantly among the 3 groups. Peak exercise time and peak VO₂ tended to be increased in the L-carnitine treatment group, and tended to be decreased in the DL-carnitine treatment group. Both LT and VT (ml/kg/min) were significantly improved (LT: from 9.7±0.6 to 10.8±1.0, p<0.05; VT: from 9.8±0.8 to 11.8±1.9, p<0.02) by the administration of L-carnitine, while LT was significantly decreased (from 11.0±2.0 to 9.6±1.2, p<0.05) and VT tended to be decreased by the administration of DL-carnitine (from 11.6±2.0 to 10.8±2.4). In the untreated control group, no significant changes were observed in the values of exercise tolerance between the 2 series of exercise testings. In neither group did carnitine modify hemodynamic parameters at rest or during exercise.
In conclusion, this study demonstrated that L-carnitine increases and DL-carnitine decreases exercise tolerance in patients with impaired exercise tolerance.