Pharmacokinetics of intravenous and oral bolus doses of L-carnitine in healthy subjects.
Level 3 - non-randomized controlled study
Non-randomized experimental pharmacokinetic study in healthy human subjects
PubMed 3234464 · doi:10.1007/BF00558253
What was done
Six healthy subjects on a low carnitine diet received single intravenous and oral boluses of 2 g and 6 g L-carnitine to evaluate plasma elimination kinetics, clearance, apparent volume of distribution, 24-hour urinary recovery, and oral bioavailability.
What was found
Intravenous 2 g vs. 6 g: - Elimination phase half-life (t1/2 beta): 6.5 h vs. 3.9 h - Elimination constant: 0.40 vs. 0.50 h-1 - Plasma carnitine clearance: 5.4 vs. 6.1 l x h-1 (p < 0.025) - Apparent volumes of distribution were not significantly different (similar to total body water) - 24-hour urinary recovery: 70% vs. 82% Oral 2 g vs. 6 g: - Plasma AUCs showed no significant difference - 24-hour urinary recovery: 8% vs. 4% - Oral bioavailability: 16% for the 2-g dose vs. 5% for the 6-g dose
Why it matters
Mucosal absorption of oral L-carnitine appears saturated at or below a 2-g dose, indicating that escalating single oral doses does not meaningfully increase systemic bioavailability.
Limits
Sample size was very small (n = 6), and all participants were healthy subjects on a controlled diet. The study examined only single bolus doses, leaving chronic dosing, steady-state pharmacokinetics, and clinical populations unaddressed.
Cited by
- supports L-carnitine is poorly absorbed when taken orally compared to injectable forms.