In a relative bioavailability study in 15 healthy adult male volunteers, levocarnitine tablets were found to be bio-equivalent to levocarnitine oral solution. Following 4 days of dosing with 6 tablets of levocarnitine 330 mg b.i.d. or 2 g of levocarnitine oral solution b.i.d., the maximum plasma concentration (Cmax) was about 80 µmol/L and the time to maximum plasma concentration (Tmax) occurred at 3.3 hours.
The plasma concentration profiles of levocarnitine after a slow 3 minute intravenous bolus dose of 20 mg/kg of levocarnitine injection were described by a two-compartment model. Following a single intravenous administration, approximately 76% of the levocarnitine dose was excreted in the urine during the 0 to 24 hour interval. Using plasma concentrations uncorrected for endogenous levocarnitine, the mean distribution half life was 0.585 hours and the mean apparent terminal elimination half life was 17.4 hours.
The absolute bioavailability of levocarnitine from the two oral formulations of levocarnitine, calculated after correction for circulating endogenous plasma concentrations of levocarnitine, was 15.1 ± 5.3% for levocarnitine tablets and 15.9 ± 4.9% for levocarnitine oral solution.
Total body clearance of levocarnitine (Dose/AUC including endogenous baseline concentrations) was a mean of 4.00 L/h.
Levocarnitine was not bound to plasma protein or albumin when tested at any concentration or with any species including the human.9
In a 9-week study, 12 ESRD patients undergoing hemodialysis for at least 6 months received levocarnitine injection 20 mg/kg three times per week after dialysis. Prior to initiation of levocarnitine injection therapy, mean plasma levocarnitine concentrations were approximately 20 µmol/L pre-dialysis and 6 µmol/L post-dialysis. The table summarizes the pharmacokinetic data (mean ± SD µmol/L) after the first dose of levocarnitine injection and after 8 weeks of levocarnitine injection therapy.
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- Trough (pre-dialysis, pre-dose)
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After one week of levocarnitine injection therapy (3 doses), all patients had trough concentrations between 54 µmol/L and 180 µmol/L (normal 40 µmol/L to 50 µmol/L) and concentrations remained relatively stable or increased over the course of the study.
In a similar study in ESRD patients also receiving 20 mg/kg levocarnitine injection 3 times per week after hemodialysis, 12- and 24-week mean pre-dialysis (trough) levocarnitine concentrations were 189 (N=25) and 243 (N=23) µmol/L, respectively.
In a dose-ranging study in ESRD patients undergoing hemodialysis, patients received 10, 20, or 40 mg/kg levocarnitine injection 3 times per week following dialysis (N~30 for each dose group). Mean ± SD trough levocarnitine concentrations (µmol/L) by dose after 12 and 24 weeks of therapy are summarized in the table.
While the efficacy of levocarnitine injection to increase carnitine concentrations in patients with ESRD undergoing dialysis has been demonstrated, the effects of supplemental carnitine on the signs and symptoms of carnitine deficiency and on clinical outcomes in this population have not been determined.