Multicenter trial of L-carnitine in maintenance hemodialysis patients. II. Clinical and biochemical effects. Since carnitine deficiency has been reported in some patients undergoing maintenance hemodialysis, we studied the effects of intravenous infusion of L-carnitine or placebo at the end of each dialysis treatment. The trial, which lasted seven months (one month baseline, 6 months treatment) was multicenter, double blind, placebo controlled, and randomized. Eighty-two long-term hemodialysis patients, who were given either carnitine (N = 38) or placebo (N = 44), completed this study. In each group, clinical and biochemical parameters during treatment were compared with baseline values. Intra-dialytic hypotension and muscle cramps were reduced only in the carnitine treated group, while improvement in post-dialysis asthenia was noticed in both carnitine and placebo groups. Maximal oxygen consumption, measured during a progressive work exercise test, improved significantly in the carnitine group (111 +/- 50 ml/min. P less than 0.03) and was unchanged in the placebo group. L-carnitine treatment was associated with a significant drop in pre-dialysis concentrations of serum urea nitrogen, creatinine and phosphorus (means +/- SEM, 101 +/- 4.5 to 84 +/- 3.9, 16.7 +/- 0.67 to 14.7 +/- 0.64, and 6.4 +/- 0.3 to 5.5 +/- 0.4 mg/dl, respectively, P less than 0.004). No significant changes in any of these variables were noticed in the placebo group. Mid-arm circumference and triceps skinfold thickness were measured in 11 carnitine and 13 placebo treated patients. Calculated mid-arm muscle area increased in the carnitine patients (41.37 +/- 2.68 to 45.6 +/- 2.82 cm2, P = 0.05) and remained unchanged in the placebo patients. 