L-carnitine in the treatment of painful diabetic neuropathy and its effecton plasma beta-endorphin levels

Objective: We investigated the efficacy of L-carnitine (LC) in the treatmen t of painful diabetic neuropathy (DN) and its effects on levels of the endo genous peptide beta -endorphin. Methods: The study group consisted of 7 diabetic patients with painful DN, 7 diabetic patients without DN, and 7 healthy control subjects. Blood sampl es were obtained from all participants for determination of basal beta -end orphin levels. A 30-mg/kg intravenous bolus injection of LC was then admini stered. DN was diagnosed by electroneuromyography, and severity of pain was evaluated on a scale from 1 (transient, very mild pain) to 4 (severe pain) . Results: Before treatment, the 7 patients with DN had pain scores of 1 (n = 1), 2 (n = 3), 3 (n = 2), and 4 (n = 1). After treatment, 3 patients had a score of 1, and 4 had a score of 2. Mean (+/- SD) basal beta -endorphin le vels were 22.6 +/- 13.02 pg/mL in the 7 patients with DN, 26.01 +/- 9.06 pg /mL in the 7 without DN, and 90.04 +/- 29.11 pg/mL in the control group (P < 0.05). In the patients with painful DN, <beta>-endorphin levels at 3 hour s and on day 15 were 31.97 +/- 11.81 pg/mL and 28.73 +/- 12.53 pg/mL, respe ctively. An acute rise in beta -endorphin levels was noted at 3 hours (P < 0.05), but patients' pain scores did not change correspondingly. The improv ement in pain scores in patients with DN after 15 days of LC treatment was not associated with any significant change in <beta>-endorphin levels. Conclusions: beta -Endorphin levels are lower in diabetic patients than in the nondiabetic population. Treatment with LC is effective in treating pain ful DN, but this effect does not appear to be mediated by alterations in be ta -endorphin levels.