Comparison of pharmacokinetics of L-carnitine, Acetyl- L-carnitine and Propionyl-Lcarnitine after single oral administration of L-carnitine in healthy volunteers

Purpose: To investigate the pharmacokinetics of L-carnitine (LC) and its analogues, acetyl-L-carnitine (ALC) and propionyl -L-carnitine (PLC) in healthy volunteers after single L-carnitine administration. Methods: Liquid L-carnitine (2.0 g) was administered orally as a single dose in 12 healthy subjects. Plasma and urine concentrations of L-carnitine, ALC and PLC were detected by HPLC. Results: The maximum plasma concentration (Cmax) and area under the curve (AUC0-?) of L-carnitine was 84.7±25.2 ?mol·L-1·h and 2676.4±708.3 ?mol·L-1·h, respectively. The elimination half-life of L-carnitine and the time required to reach the Cmax (Tmax) was 60.3±15.0 and 3.4±0.46 h, respectively. The Cmax of ALC (12.9±5.5 ?mol·L-1) and PLC (5.08±3.08 ?mol·L-1) was lower than L-carnitine (P < 0.01), so as the AUC0-? (166.2±77.4 and 155.6±264.2?mol·L-1·h, respectively, P < 0.01). The half-life of ALC (35.9±28.9h) and PLC (25.7±30.3 h) was also shorter than L-carnitine (P < 0.01). The 24h accumulated urinary excretion of L-carnitine, ALC and PLC were 613.5±161.7, 368.3±134.8 and 61.3±37.8?mol, respectively. Conclusion: L-carnitine has a greater maximum plasma concentration than ALC and PLC. L-carnitine also has a longer half-life than ALC and PLC. These data may have important implications in the designing of dosing regimens for L-carnitine or its analogues, such as ALC or PLC.