What is Ketamine?
Ketamine (brand name: ketalar) is a dissociative injected anesthetic (blocks sensory perception) that has been available by prescription in the U.S. since the 1970s for human and veterinary uses. Esketamine (Spravato), the S-enantiomer of racemic ketamine, was approved in 2019 for treatment-resistant depression and is approved for use in depressed patients with acute suicidal ideation or behavior. Ketaset is the brand name of a surgical anesthesia used by veterinarians.
Dissociative drugs can lead to distortion of sights, colors, sounds, self, and one’s environment. Ketamine is available in a clear liquid or off-white powder form for intravenous injection or as a nasal spray. Examples of other dissociative drugs include phencyclidine (PCP) and dextromethorphan (DXM).
In the U.S., ketamine is classified as a schedule III drug under the DEA Controlled Substances Act; however, it is not classified as an opioid (narcotic) or barbiturate.
Why is Ketamine Used Medically?
- Ketamine can provide pain relief and short-term memory loss (for example, amnesia of a medical procedure).
- In surgery, it is used as an induction and maintenance agent for sedation and to provide general anesthesia.
- It has also been used for pain control in burn therapy, battlefield injuries, and in children who cannot use other anesthetics due to side effects or allergies.
- Ketamine, through blocking at the N-methyl-D-aspartate (NMDA) site, has rapid action in controlling symptoms of depression and acute suicidal ideation.
- At normal doses, it is often preferred as an anesthetic in patients at risk of bronchospasm and respiratory depression.
Pharmacology of Ketamine
Ketamine is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, and it blocks HCN1 receptors. However, at higher doses it may also bind to the opioid mu and sigmareceptors. It disrupts the neurotransmitter (brain chemical) glutamate. Glutamate is involved with learning, memory, emotion, and pain recognition. It can exhibit sympathomimetic activity which can lead to rapid heart rate and elevated blood pressure.
It is related to Phencyclidine (PCP), but has less than 10% of the potency of pure PCP.
This agent is a lipid soluble compound, has an initial rapid distribution and large volume of distribution, with a half-life of 10 to 15 minutes. Secondarily, the drug distributes into peripheral tissues with a slower elimination half-life of up to 3 hours, undergoes hepatic metabolism and is excreted in the urine.
How Quickly Does Ketamine Work?
- An injection yields a quick response, with effects occurring in seconds to minutes.
- “Snorting” leads to effects in roughly 5 to 15 minutes (this is the most common method of abuse).
- Oral consumption requires between 5 and 30 minutes.
The effects of abuse typically last 1 to 2 hours, but the users judgement, senses and coordination may be affected for up to 24 hours or longer. Sensations the user may seek include floating, stimulation and visual effects.
High doses may dangerously reduce breathing, lead to muscle spasms or weakness, dizziness, balance difficulty, impaired vision, slurred speech, nausea and vomiting, and severe confusion.
Binge use, where the user indulges in the drug in excess amounts in a short period of time has been reported, as well.
- With an overdose of ketamine, emergency care, such as 911, should be contacted immediately.
- There is no antidote for this drug. Overdose situations are treated with symptomatic and supportive care in the hospital setting. In the emergency department, adverse effects typically resolve in 1 to 3 hours.
- Benzodiazepines such as lorazepam may be used if needed for seizures, excitation, or muscle rigidity.
- Respiratory support is rarely needed, but assisted ventilation or supplemental oxygen may be required. Respiratory depression may be more likely if combined with sedatives.
- Those who abuse this drug should be referred for drug counseling.