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Carnitor Injection (Sigma-Tau)
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CARNITOR® (levocarnitine) is a carrier molecule in the transport of long-chain fatty acids across the inner mitochondrial membrane.
The chemical name of levocarnitine is 3-carboxy-2( R )-hydroxy-N,N,N-trimethyl-1-propanaminium, inner salt. Levocarnitine is a white crystalline, hygroscopic powder. It is readily soluble in water, hot alcohol, and insoluble in acetone. The specific rotation of levocarnitine is between -29° and -32°. Its chemical structure is:
CARNITOR® (levocarnitine) Injection is a sterile aqueous solution containing 1 g of levocarnitine per 5 mL vial. The pH is adjusted to 6.0-6.5 with hydrochloric acid or sodium hydroxide.
CARNITOR® (levocarnitine) is a naturally occurring substance required in mammalian energy metabolism. It has been shown to facilitate long-chain fatty acid entry into cellular mitochondria, thereby delivering substrate for oxidation and subsequent energy production. Fatty acids are utilized as an energy substrate in all tissues except the brain. In skeletal and cardiac muscle, fatty acids are the main substrate for energy production.
Primary systemic carnitine deficiency is characterized by low concentrations of levocarnitine in plasma, RBC, and/or tissues. It has not been possible to determine which symptoms are due to carnitine deficiency and which are due to an underlying organic acidemia, as symptoms of both abnormalities may be expected to improve with CARNITOR®. The literature reports that carnitine can promote the excretion of excess organic or fatty acids in patients with defects in fatty acid metabolism and/or specific organic acidopathies that bioaccumulate acylCoA esters. 1-6
Secondary carnitine deficiency can be a consequence of inborn errors of metabolism or iatrogenic factors such as hemodialysis. CARNITOR® may alleviate the metabolic abnormalities of patients with inborn errors that result in accumulation of toxic organic acids. Conditions for which this effect has been demonstrated are: glutaric aciduria II, methyl malonic aciduria, propionic acidemia, and medium chain fatty acylCoA dehydrogenase deficiency. 7,8 Autointoxication occurs in these patients due to the accumulation of acylCoA compounds that disrupt intermediary metabolism. The subsequent hydrolysis of the acylCoA compound to its free acid results in acidosis which can be life-threatening. Levocarnitine clears the acylCoA compound by formation of acylcarnitine, which is quickly excreted. Carnitine deficiency is defined biochemically as abnormally low plasma concentrations of free carnitine, less than 20 µmol/L at one week post term and may be associated with low tissue and/or urine concentrations. Further, this condition may be associated with a plasma concentration ratio of acylcarnitine/levocarnitine greater than 0.4 or abnormally elevated concentrations of acylcarnitine in the urine. In premature infants and newborns, secondary deficiency is defined as plasma levocarnitine concentrations below age-related normal concentrations.
End Stage Renal Disease (ESRD) patients on maintenance hemodialysis may have low plasma carnitine concentrations and an increased ratio of acylcarnitine/carnitine because of reduced intake of meat and dairy products, reduced renal synthesis and dialytic losses. Certain clinical conditions common in hemodialysis patients such as malaise, muscle weakness, cardiomyopathy and cardiac arrhythmias may be related to abnormal carnitine metabolism.
Pharmacokinetic and clinical studies with CARNITOR® have shown that administration of levocarnitine to ESRD patients on hemodialysis results in increased plasma levocarnitine concentrations.
In a relative bioavailability study in 15 healthy adult male volunteers, CARNITOR® Tablets were found to be bio-equivalent to CARNITOR® Oral Solution. Following 4 days of dosing with 6 tablets of CARNITOR® 330 mg b.i.d. or 2 g of CARNITOR® oral solution b.i.d., the maximum plasma concentration (C max ) was about 80 µmol/L and the time to maximum plasma concentration (T max ) occurred at 3.3 hours.
The plasma concentration profiles of levocarnitine after a slow 3 minute intravenous bolus dose of 20 mg/kg of CARNITOR® were described by a two-compartment model. Following a single i.v. administration, approximately 76% of the levocarnitine dose was excreted in the urine during the 0-24h 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 CARNITOR®, calculated after correction for circulating endogenous plasma concentrations of levocarnitine, was 15.1 ± 5.3% for CARNITOR® Tablets and 15.9 ± 4.9% for CARNITOR® 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 CARNITOR® 20 mg/kg three times per week after dialysis. Prior to initiation of CARNITOR® 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 CARNITOR® and after 8 weeks of CARNITOR® therapy.
After one week of CARNITOR® therapy (3 doses), all patients had trough concentrations between 54 and 180 µmol/L (normal 40-50 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 CARNITOR® 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 CARNITOR® 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 CARNITOR® 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.
METABOLISM AND EXCRETION
In a pharmacokinetic study where five normal adult male volunteers received an oral dose of [ 3 H-methyl]-L-carnitine following 15 days of a high carnitine diet and additional carnitine supplement, 58 to 65% of the administered radioactive dose was recovered in the urine and feces in 5 to 11 days. Maximum concentration of [ 3 H-methyl]-L-carnitine in serum occurred from 2.0 to 4.5 hr after drug administration. Major metabolites found were trimethylamine N-oxide, primarily in urine (8% to 49% of the administered dose) and [ 3 H]-(gamma)-butyrobetaine, primarily in feces (0.44% to 45% of the administered dose). Urinary excretion of levocarnitine was about 4 to 8% of the dose. Fecal excretion of total carnitine was less than 1% of the administered dose. 10
After attainment of steady state following 4 days of oral administration of CARNITOR® Tablets (1980 mg q12h) or Oral Solution (2000 mg q12h) to 15 healthy male volunteers, the mean urinary excretion of levocarnitine during a single dosing interval (12h) was about 9% of the orally administered dose (uncorrected for endogenous urinary excretion).
INDICATIONS AND USAGE
For the acute and chronic treatment of patients with an inborn error of metabolism which results in secondary carnitine deficiency.
For the prevention and treatment of carnitine deficiency in patients with end stage renal disease who are undergoing dialysis. (US Patent Nos. 6,335,369; 6,429,230; 6,696,493)
The safety and efficacy of oral levocarnitine has not been evaluated in patients with renal insufficiency. Chronic administration of high doses of oral levocarnitine in patients with severely compromised renal function or in ESRD patients on dialysis may result in accumulation of the potentially toxic metabolites, trimethylamine (TMA) and trimethylamine-N-oxide (TMAO), since these metabolites are normally excreted in the urine.
Carcinogenesis, mutagenesis, impairment of fertility
Mutagenicity tests performed in Salmonella typhimurium, Saccharomyces cerevisiae , and Schizosaccharomyces pombe indicate that levocarnitine is not mutagenic. No long-term animal studies have been performed to evaluate the carcinogenic potential of levocarnitine.
There have been no reports of toxicity from levocarnitine overdosage. Levocarnitine is easily removed from plasma by dialysis. The intravenous LD 50 of levocarnitine in rats is 5.4 g/kg and the oral LD 50 of levocarnitine in mice is 19.2 g/kg. Large doses of levocarnitine may cause diarrhea.
CARNITOR® Injection is administered intravenously.
The recommended dose is 50 mg/kg given as a slow 2-3 minute bolus injection or by infusion. Often a loading dose is given in patients with severe metabolic crisis, followed by an equivalent dose over the following 24 hours. It should be administered q3h or q4h, and never less than q6h either by infusion or by intravenous injection. All subsequent daily doses are recommended to be in the range of 50 mg/kg or as therapy may require. The highest dose administered has been 300 mg/kg.
It is recommended that a plasma carnitine concentration be obtained prior to beginning this parenteral therapy. Weekly and monthly monitoring is recommended as well. This monitoring should include blood chemistries, vital signs, plasma carnitine concentrations (the plasma free carnitine concentration should be between 35 and 60 µmol/L) and overall clinical condition.
The recommended starting dose is 10-20 mg/kg dry body weight as a slow 2-3 minute bolus injection into the venous return line after each dialysis session. Initiation of therapy may be prompted by trough (pre-dialysis) plasma levocarnitine concentrations that are below normal (40-50 µmol/L). Dose adjustments should be guided by trough (pre-dialysis) levocarnitine concentrations, and downward dose adjustments (e.g. to 5 mg/kg after dialysis) may be made as early as the third or fourth week of therapy.
Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
CARNITOR® Injection is compatible and stable when mixed in parenteral solutions of Sodium Chloride 0.9% or Lactated Ringer's in concentrations rang-ing from 250 mg/500 mL (0.5 mg/mL) to 4200 mg/500 mL (8.0 mg/mL) and stored at room temperature (25°C) for up to 24 hours in PVC plastic bags.
CARNITOR® (levocarnitine) Injection is available in 1 g per 5 mL single dose vials packaged 5 vials per carton (NDC 54482-147-01). CARNITOR® (levocarnitine) Injection 5 mL vial is manufactured for Sigma-Tau Pharmaceuticals, Inc. by Sigma-Tau S.p.A., 00040 Pomezia (Rome), Italy or Chesapeake Biological Laboratories, Inc. Baltimore, MD 21230-2591.
Store vials at controlled room temperature (25°C). See USP. Discard unused portion of an opened vial, as the formulation does not contain a preservative.
CARNITOR® (levocarnitine) is also available in the following dosage forms:
CARNITOR® (levocarnitine) Tablets are supplied as 330 mg tablets embossed with "CARNITOR ST" in blister packages, in boxes of 90 tablets (NDC 54482-144-07). Made in Italy.
CARNITOR® (levocarnitine) Oral Solution is supplied in 118 mL (4 FL. OZ.) multiple-unit plastic containers. The multiple-unit containers are packaged 24 per case (NDC 54482-145-08). CARNITOR® (levocarnitine) Oral Solution is manufactured for Sigma-Tau Pharmaceuticals, Inc. by Hi-Tech Pharmacal Co., Inc., Amityville, NY 11701.
Gaithersburg, MD 20877
PREVIOUS EDITION IS OBSOLETE
Date of Issue: 03/04 VPI-10