KETALAR (Page 3 of 4)

10 Overdosage

Changes in heart rate and blood pressure, respiratory depression, and apnea may occur with overdosage or by a rapid rate of administration of KETALAR. Monitor patients for clinically relevant changes in heart rate and blood pressure. Assisted ventilation, including mechanical ventilation, may be required.

In cases of unintentional overdose of KETALAR (up to ten times that usually required), patients had a prolonged but complete recovery.

11 Description

KETALAR (ketamine hydrochloride) injection, for intravenous or intramuscular use, contains ketamine, a nonbarbiturate general anesthetic. Ketamine hydrochloride, USP is a white crystalline powder and has a molecular formula of C13H16ClNO•HCl and a molecular weight of 274.19. The chemical name for ketamine hydrochloride is (±)-2-(o-Chlorophenyl)-2-(methylamino)cyclohexanone hydrochloride. The chemical structure of ketamine hydrochloride is:

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ketamine hydrochloride

It is formulated as a slightly acidic (pH 3.5-5.5) sterile solution for intravenous or intramuscular injection. Each milliliter (mL) of the multiple-dose vials contain either 10 mg ketamine base (equivalent to 11.53 mg ketamine hydrochloride), 50 mg ketamine base (equivalent to 57.67 mg ketamine hydrochloride) or 100 mg ketamine base (equivalent to 115.33 mg ketamine hydrochloride) and not more than 0.10 mg/mL benzethonium chloride added as a preservative in water for injection. The 10 mg/mL solution has been made isotonic with 6.60 mg sodium chloride.

12 Clinical Pharmacology

12.1 Mechanism of Action
KETALAR, a racemic mixture of ketamine, is a non-selective, non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, an ionotropic glutamate receptor. The major circulating metabolite of ketamine (norketamine) demonstrated activity at the same receptor with less affinity. Norketamine is about 1/3 as active as ketamine in reducing halothane requirements (MAC) of the rat.

12.2 Pharmacodynamics
Nervous System
Ketamine is a rapidly-acting general anesthetic producing a dissociative anesthetic state characterized by profound analgesia, normal pharyngeal-laryngeal reflexes, normal or slightly enhanced skeletal muscle tone, cardiovascular and respiratory stimulation, and occasionally a transient and minimal respiratory depression. The mechanism of action is primarily due to antagonism of N-methyl-D-aspartate (NMDA receptors) in the central nervous system.

Ketamine can produce nystagmus with pupillary dilation, salivation, lacrimation, and spontaneous limb movements with increased muscle tone through indirect sympathomimetic activity. Ketamine produces analgesia. Ketamine-induced emergence delirium can be reduced with benzodiazepines.

Cardiovascular System
Ketamine increases blood pressure, heart rate, and cardiac output. Cardiovascular effects of ketamine are indirect and believed to be mediated by inhibition of both central and peripheral catecholamine reuptake. Elevation of blood pressure reaches a maximum within a few minutes of injection and usually returns to preanesthetic values within 15 minutes. In the majority of cases, the systolic and diastolic blood pressure peaks from 10% to 50% above preanesthetic levels shortly after induction of anesthesia, but the elevation can be higher or longer in individual cases.

Respiratory System
Ketamine is a potent bronchodilator suitable for anesthetizing patients at high risk for bronchospasm.

12.3 Pharmacokinetics
Distribution
Following intravenous administration, the ketamine concentration has an initial slope (alpha phase) lasting about 45 minutes with a half-life of 10 to 15 minutes. This first phase corresponds clinically to the anesthetic effect of the drug.

Elimination
Metabolism
Ketamine is metabolized via N-dealkylation to the active metabolite norketamine primarily by CYP2B6 and CYP3A4 and to a lesser extent by other CYP enzymes. Norketamine undergoes hydroxylation of the cyclohexone ring to form hydroxynorketamine compounds via CYP-dependent pathways, which are conjugated with glucuronic acid and subsequently undergo dehydration of the hydroxylated metabolites to form the cyclohexene derivative dehydroxynorketamine.

Excretion
Following intravenous administration, the ketamine concentration decreases due to a combination of redistribution from the CNS to slower equilibrating peripheral tissues and hepatic biotransformation to norketamine. The redistribution half-life of ketamine from the CNS to slower equilibrating peripheral tissues (beta phase) is 2.5 hours.

13 Nonclinical Toxicology

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility
Carcinogenesis
Long-term animal studies have not been conducted to evaluate the carcinogenic potential of ketamine.

Mutagenesis
In a published report, ketamine was clastogenic in the in vitro chromosomal aberration assay.

Impairment of Fertility
Adequate studies to evaluate the impact of ketamine on male or female fertility have not been conducted. Male and female rats were treated with 10 mg/kg ketamine IV (0.8 times the average human induction dose of 2 mg/kg IV based on body surface area) on Days 11, 10, and 9 prior to mating. No impact on fertility was noted; however, this study design does not adequately characterize the impact of a drug on fertility endpoints.

13.2 Animal Toxicology and/or PharmacologyPublished studies in animals demonstrate that the use of anesthetic agents during the period of rapid brain growth or synaptogenesis results in widespread neuronal and oligodendrocyte cell loss in the developing brain and alterations in synaptic morphology and neurogenesis. Based on comparisons across species, the window of vulnerability to these changes is believed to correlate with exposures in the third trimester through the first several months of life, but may extend out to approximately 3 years of age in humans.

In primates, exposure to 3 hours of an anesthetic regimen that produced a light surgical plane of anesthesia did not increase neuronal cell loss, however, treatment regimens of 5 hours or longer increased neuronal cell loss. Data in rodents and in primates suggest that the neuronal and oligodendrocyte cell losses are associated with subtle but prolonged cognitive deficits in learning and memory. The clinical significance of these nonclinical findings is not known, and healthcare providers should balance the benefits of appropriate anesthesia in neonates and young children who require procedures against the potential risks suggested by the nonclinical data [see Warnings and Precautions (5.5), Use in Specific Populations (8.1, 8.4)].

In published studies, intraperitoneal administration of ketamine at doses greater than 40 mg/kg induced vacuolation in neuronal cells of the posterior cingulate and retrosplenial cortices in adult rats, similar to what has been reported in rodents administered other NMDA receptor antagonists. These vacuoles were demonstrated to be reversible and did not progress to degeneration or neuronal death up to doses of 80 mg/kg (1.2 times the human dose of 10 mg/kg based on body surface area). A no-effect level for neuronal vacuolation was 20 mg/kg intraperitoneal (0.3 times a human dose of 10 mg/kg on a body surface area basis). The window of vulnerability to these changes is believed to correlate with exposures in humans from the onset of puberty through adulthood. The relevance of this finding to humans is unknown.

14 Clinical Studies

KETALAR has been studied in over 12,000 operative and diagnostic procedures, involving over 10,000 patients in 105 separate studies. During the course of these studies, KETALAR was administered as the sole general anesthetic, as an induction agent prior to administration of other general anesthetics, or to supplement other anesthetic agents.

KETALAR has been evaluated during the following procedures:

  1. debridement, dressing changes, and skin grafting in burn patients, as well as other superficial surgical procedures.
  2. neurodiagnostic procedures such as myelograms and lumbar punctures.
  3. diagnostic and operative procedures of the ear, nose, and mouth, including dental extractions.
  4. sigmoidoscopy and minor surgery of the anus and rectum, and circumcision.
  5. extraperitoneal procedures, such as dilatation and curettage.
  6. orthopedic procedures such as closed reductions, manipulations, femoral pinning, amputations, and biopsies.
  7. cardiac catheterization procedures.

16 How Supplied/Storage And Handling

How Supplied

KETALAR injection is a clear, colorless solution supplied as the hydrochloride salt in concentrations equivalent to ketamine base, as follows:

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Storage and Handling

KETALAR injection should be stored at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C to 30°C (59°F to 86°F) [see USP Controlled Room Temperature]. Protect from light.

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