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Abstract
Clinical observations have suggested that carnitine supplementation may be beneficial
to a subset of patients receiving chronic hemodialysis. In the absence of definitive
clinical trials, the clinician must decide for an individual patient whether a trial
of carnitine therapy is justified. The institution of carnitine therapy is further
complicated by the availability of oral and intravenous dosing forms and by the compound's
complex pharmacokinetics. The oral systemic bioavailability of carnitine in normal
subjects is 5% to 16%, with peak plasma carnitine concentrations reached 2 to 6 hours
after dosing. Carnitine is initially distributed into extracellular water and then
more slowly enters tissue compartments with complex kinetics. Elimination of carnitine
is through the urine or dialysate. Intravenous carnitine administration results in
large peak plasma concentrations and assures systemic bioavailability. Orally administered
carnitine has been reported to have clinical efficacy in hemodialysis patients in
doses of 2 to 4 g per day in divided doses. Intravenous carnitine has also been widely
used in clinical trials in attempts to demonstrate efficacy in the hemodialysis population;
however, the available data do not establish the superiority of the intravenous formulation
over the oral form. Intravenous carnitine may have theoretical advantages in initiating
treatment when high peak concentrations are required to facilitate carnitine reaching
nonhepatic tissue sites or when oral carnitine therapy is not feasible due to poor
tolerance or compliance. Although comparative trials are lacking, it is probable that
oral therapy can be used for long-term maintenance, regardless of which formulation
was used to initiate therapy. The decision to use carnitine therapy, as well as the
dose and route of administration, requires individualization based on the clinical
status of the patient and the goals of therapy.
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© 1995 Published by Elsevier Inc.
