EFFECTS OF L-CARNITINE AND DL-CARNITINE ON PATIENTS WITH IMPAIRED EXERCISE TOLERANCE

We designed this study to determine whether orally administered L- and DL-carnitine can improve exercise tolerance in a group of patients wi th exercise intolerance. Nineteen patients with cardiac disease were r andomly divided into 2 groups, an L-carnitine treatment group (n = 9) and a DL-carnitine treatment group (n = 10). Eight additional age-matc hed patients served as an untreated control group. Subjects in both ca rnitine treatment groups underwent cardiopulmonary exercise testing on a cycle ergometer in order to determine peak exercise time, peak oxyg en uptake (VO2), lactate threshold (LT) and ventilatory threshold (VT) before and after the oral administration of 900 mg/day of L- or DL-ca rnitine 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 signif icantly 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 signif icant changes were observed in the values of exercise tolerance betwee n the 2 series of exercise testings. In neither group did carnitine mo dify hemodynamic parameters at rest or during exercise. In conclusion, this study demonstrated that L-carnitine increases and DL-carnitine d ecreases exercise tolerance in patients with impaired exercise toleran ce.