Ketamine Troches

Ketamine is mainly used in both veterinary and human clinical anesthesia serving as pain killer, sedation in intensive care, and induction of memory loss. It produces a wide variety of pharmacological effects including sedation, catalepsy, somatic analgesia, bronchodilation and stimulation of the sympathetic nervous system. It usually comes as a white crystalline powder and can also be formulated into tablets and pills. Ketamine is widely administered intravenously, intramuscularly, orally and nasally by emergency physicians as a short acting pain-reducer. It also relaxes smooth muscles in the airways and may therefore be a useful induction agent in children with asthma.

Ketamine can be swallowed or injected. Ketamine currently has a wide variety of clinical applications because of its beneficial peculiar clinical and pharmacological properties. The preceding characteristics of the drug has made it survive through the ages for more than half a century with even new-found clinical applications. Its newly discovered neuroprotective, anti-inflammatory and anti-tumor effects and the now-known usefulness of low dose ketamine regimens have helped to expand the clinical application profile of the drug.

When administered, the pharmacological impact of the medication can last for 45 – 90 minutes. The onset of effect depends on the route of administration – ranging from as little as 30 seconds to as much as 20 minutes. The effects kick-in at just about 30 seconds when injected and up to 20 minutes when administered orally. An equivalent dose to 2 mg of the medication per kg body-weight given through the intravenous route over 60 seconds produces surgical anesthesia within 30 seconds lasting for 5-10 minutes (dose may range from 1 to 4.5 mg/kg); an intramuscular dose equivalent to 10 mg per kg body-weight (range 6.5-13 mg/kg) usually produces surgical anesthesia within 3 to 4 minutes lasting for 12 to 25 minutes.

Analgesia is obtained by administration of 0.2-0.75 mg/kg intravenously. Ketamine is known to produce psychotropic effects in clinical settings when administered via intramuscular injection in doses between 25 to 200 mg. Given nasally its bioavailability in children is about 50%, while its approximately 93% when administered via the intramuscular route.

Several studies investigated the local tolerance of ketamine when administered intrathecally. Ketamine, when injected without preservative did not cause neurotoxicity in the spinal cord of swine or rabbits.

Ketamine has been utilized in short-term medical procedures that do not require skeletal muscle relaxation, and it has the approval for induction of general anesthesia as a pre-anesthetic to other general anesthetic agents.

It also has been supplemented with low-potency agents such as nitrous oxide. It may be utilized for procedures requiring reduction of fractures and dislocations.

Ketamine is a promising treatment for some cases of major depression, which is the leading cause of disability worldwide. Studies have asserted that patients who respond to ketamine may rapidly reduce suicidality, that is, life-threatening thoughts and acts. It also may be effective for treating depression combined with anxiety.

Clinically, the medication is administered by intramuscular or intravenous injection. For analgesia, the intrathecal route is used as well. Also, the oral and the rectal routes have been described.

Ketamine has been in clinical use for over half a century, yet its precise mechanisms of action remain largely unknown. Ketamine exerts its effect mainly by the noncompetitive antagonism of the N-methyl D-aspartic acid (NMDA) receptor. As wells as having local anesthetic effects, it also interacts with opioid receptors, monoamine, cholinergic, purinergic and adrenoreceptor systems. NMDA receptor interaction with ketamine is thought to play a role in its opioid induced effect of blocking high sensitivity to pain and subanesthetic doses of ketamine via NMDA receptor blockade potentiate opioid analgesia. In addition, ketamine by suppressing the induction of nitric oxide synthase activity and protein expression by endotoxin provides anti-inflammatory effect against infection. Whereas the hypnotic effects of ketamine are caused by a combination of immediate channel blockade of NMDA and hyperpolarization-activated cation channels.

In macrophages, ketamine reduces the expression of alpha tumor necrosis factor and interleukin-6 gene. Through blocking NMDA receptor, ketamine inhibits the extracellular signal regulated kinase ½ pathway and reduces the growth of cancer cells. Ketamine’s post-drug effects such as increase in synaptic connectivity causes the prolonged antidepressant effects associated with the drug.

Ketamine may cause central nervous system depression; caution should be applied when operating heavy machinery; do not engage in hazardous activities or operate hazardous machinery for at least 24 hours after usage.

Ketamine may cause dependence and tolerance with prolonged use; discontinuation of long-term use has been associated with a withdrawal syndrome with psychotic features.

There is no data on the measurement of ketamine in breast milk post-administration in humans. Limited information suggests that ketamine does not affect infants through breastfeeding. Ketamine, due to the paucity of information should be administered to nursing mothers or during pregnancy with adequate monitoring by a physician.

This medication may interact and cause some risk when taken together with other medications. Users must consult their healthcare provider for more information on possible interactions with other medications.

Ketamine is an anesthetic with a good safety profile. Its major drawback, limiting its clinical use, is the occurrence of emergence reactions. Emergence phenomena include hallucinations, vivid dreams, floating sensations and delirium which are reduced by the simultaneous administration of benzodiazepines and keeping the patient in low stimulus environment. Such reactions are also thought to be reduced by providing adequate information about such possible adverse reactions well in advance. These effects occur in greater frequency in adults (30-50%) than in children (5-15%).

No adverse outcomes were noted in nine healthy children treated in the emergency department. Inadvertent ketamine overdose of 9 children in emergency units did not result in adverse outcomes. The overdoses were reported in the ranges of 5 to 100 times the normal dose. Toxicity manifested as prolonged sedation in all nine children; toxic effects were limited to prolonged sedation and depression of respiration in 4 of the children. The safety margin of overdose is thought to be wide.

The co-administration of ketamine resulted in serious depression of the respiratory system in two cases. Earlier administration of secobarbital in a seven-year-old patient given a little dose of ketamine in one case; while the second case involved ethanol resulting in death.

Sympathomimetic effects and serious side effects such as hypertension and lung edema have been reported. Such adverse effects appear to be rare and may be related to the combination of ketamine with other substances of abuse.

On the other hand, cardio-depressant effects have been noted in critically ill patients. This may be due to chronic catecholamine depletion and so preventing any sympathomimetic effects of ketamine and unmasking a negative effect, which is usually overshadowed by sympathetic stimulation.

It has been shown that after prolonged and/or repeated infusion of S(+)ketamine liver injury may occur.

Store this medication at 68°F to 77°F (20°C to 25°C) and away from heat, moisture and light. Keep all medicine out of the reach of children. Throw away any unused medicine after the beyond use date. Do not flush unused medications or pour down a sink or drain.

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