Comparison of pharmacokinetics of L-carnitine, acetyl-L-carnitine and propionyl-L-carnitine 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 (AUC 0-infinity) of L-carnitine was 84.7+/-25.2 micromol x L(-1) x h and 2676.4+/-708.3 micromol x L(-1) x 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 micromol x L(-1)) and PLC (5.08+/-3.08 micromol x L(-1)) was lower than L-carnitine (P < 0.01), so as the AUC 0-infinity (166.2+/-77.4 and 155.6+/-264.2 micromol x L(-1) x 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 micromol, 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.