Ketamine: Physiological effects

Last modified: Sunday, 31. May 2009 - 4:46 pm

Reported physical effects of ketamine use include an initial energy rush, numbness, and irregular muscle coordination. Large amounts can cause anesthesia and muscle spasm. Eating and drinking alcohol before taking ketamine (as with other anesthetics) may cause vomiting. If this is combined with unconsciousness, there is an acute danger of choking or death.
As an anesthetic, ketamine increases sympathetic nervous activity, which results in an increased heart rate, increased blood pressure, some dilation of bronchial tubes, pupil dilation, and related secondary effects.
Specifically, blood pressure rises by about 25%, and the heart rate is increased in the area of 20%. There is wide variation in the kinds of responses individuals can have to the drug, and occasionally, alarming increases in blood pressure can occur.
At low and moderate (subanesthetic) doses, users have difficulty walking; balance and muscle control are compromised. Vision is blurred and distorted, which can worsen a user’s disorientation. Speech is slurred, and there is numbness in the extremities. At higher dosages, standing becomes difficult or impossible. Users are prone to collapse and may lapse in and out of consciousness.
Harmful side effects
Multiple, repeated dosing of ketamine is common by most users, as is its combination with other drugs. Too many “bumps” in a row or within a small window of time frequently knocks users out cold, putting them into the anesthetic condition for which the drug was manufactured. This K-hole can last up to two hours or more, depending on the dose. The K-hole is frequently preceded by nausea or vomiting.
Adverse effects noted with the anesthetic use of ketamine include the sudden loss of respiratory function, spasms of the trachea or larynx, and vomiting. Literature on the emergency treatment of ketamine overdose is rare. Clinical recommendations advise making sure the airway is clear, that breathing is continually monitored, and that the heart rate remains steady.
On its own, ketamine toxicity is less of a concern than accidents caused by the intensity of the dissociative state and loss of muscle coordination and control. However, given that ketamine is frequently taken with other drugs such as alcohol or ecstasy, clinical reports on the dangers of its recreational use are probably inadequate.
A study conducted in Britain reported that ketamine’s impact on short- and long-term memory can linger for up to three days after a dose. Researchers looked at a broad array of memory functions, word association and language tests, attention span, and other factors related to mood. Though some recovery was noted 72 hours after ketamine usage, the researchers noted lasting impairments related to language and some aspects of memory.
Injecting ketamine intramuscularly carries with it risks common to cocaine and heroin addicts and other injection-drug users. Sharing needles can lead to the transmission of blood-borne viral infections such as HIV and hepatitis B and C, as well as increased risk of escalation of drug use and overdose.
Long-term health effects
A review of current data suggests all dissociative anesthetics cause brain damage if used heavily. Dissociatives include ketamine, dextromethorphan (or DXM), phencyclidine (PCP or angel dust), nitrous oxide (whippets) and dizocilpine (MK-801). All are N-methyl-D-aspartate (NMDA) antagonists, meaning they temporarily block a crucial neurotransmitter in the brain.
Research conducted by Dr. J.W. Olney revealed the existence of small vacuoles (essentially, very tiny holes) in the brains of mice given high doses of dizocilpine or MK-801. The tiny holes are now called Olney’s lesions and the condition is formally referenced in the medical community as NMDA antagonist neurotoxicity or NAN. NAN has also been tied to ketamine and PCP use, even in commonly-used doses.
Though more study is needed, reports of ketamine-related brain damage are growing more numerous, and the types of impairment people report experiencing (slurred speech, memory loss, difficulty concentrating) are directly tied to the centers of the brain most affected by the drug.
All dissociative anesthetics are extremely toxic to developing fetuses and should never be used during pregnancy. Severe brain damage and mental retardation may result.

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