Discovered by Parke Davis Co in the early 1960's as an alternative to their other anaesthetic PCP, which had been associated with neurotoxicity and bizzarre psycho-side effects - These psycho-side effects may be desireable for recreational drug users, but were often terrifying for medical patients, many of whom complained after recovering from surgery. Ketamine produces similar effects to PCP at a dose ratio of 4/1 (ketamine/pcp). PCP was eventually removed from the market and replaced with ketamine, which is used in both humans and animals.
Use:
Most commonly given in the hospital setting. Low doses produce analgesia while higher doses produce anaesthesia. Ketamine is unique in that with anaesthetic doses it produces stimulation of vital functions rather than depression.
Used as a general anaesthetic/analgesic during surgery, along with other basic components of anaesthesia such as opioid analgesics, sedatives and neuromuscular blocking agents.
Widely used in veterinary medicine as an anaesthetic & analgesic.
Used as a supplement to epidural anaesthesia/analgesia typically by the IV route.
Also given alone or with additional drugs for procedural sedation and emergency analgesia in a field setting (i.e. auto-accidents with trapped subjects & in military combat zones). Its use in trauma is because of its ability to increase or maintain cardiac output, which is especially desireable in cases of blood loss where a subject's blood volume is unknown. It is often preferred in the absence of ventilation equipment due to its lack of respiratory depressant effect.
Ketamine is widely used as a veterinary anaesthetic.
Low doses are useful in relieving neuropathic pain. Low doses may be given as a supplement to narcotics in cases of neuropathic, cancer related, or other forms of severe pain.
Off label or investigational uses include Complex Regional Pain Syndrome and alcohol & opioid addiction.
Observed to be particularly effective in relieving symptoms of refractory major depression. Single parenteral doses of ketamine have been shown to produce significant relief of symptoms within hours of injection, lasting up to a week after injection - This was observed in multiple subjects with major depressive disorder which had consistently failed to respond to other treatments.
NMDA receptor antagonist, sigma receptor agonist and dopamine reuptake inhibitor. Shows a weak affinity for the mu receptor in high doses. Its primary action at the NMDA receptor blocks the actions of glutamate binding, thereby preventing signal transduction between neurons in certain areas.
Molecular analogue of PCP. Chemically it is a bicyclic ketone compound with an arylcyclohexylamine core. It is chemically designated ((RS)-2-(2-Chlorophenyl)-2-(methylamino)cyclohexanone).
Racemic compound composed of an (R) enantiomer and an (S) enantiomer. (S)-ketamine has stronger sedative & analgesic properties with 4x greater affinity for the NMDA (PCP-subtype) receptor - (S) is sometimes used as a single isomer product. (R)-ketamine is a stronger sigma agonist than the (S) enantiomer. Actions at the sigma receptor are believed to lower the seizure threshold.
Effects
Ketamine is very short acting. Effects generally last 30 to 60 minutes by any route.
Produces dissociative anaesthesia. As such, its effects differ in nature from drugs of the tryptamine or phenethylamine classes, (which could more likely be considered "hallucinogens" in the proper sense). Instead, dissociatives such as ketamine produce a dose dependent separation of the conscious mind from sensory perception of one's body & surroundings, in some cases allowing a user to experience complete depersonalization - characterized by the complete loss of one's sense of identity, unawareness or oblivion to the outer world, and a shockingly realistic experience of alternate realities or dimensions which exist only inside one's brain chemistry - or as some have theorized, a reality which exists outside of space & time or inside one's soul. Some may speculate that such an experience serves as a glimpse of one's reality before existence & birth, or what one might experience after death.
Effects in low to moderate doses include analgesia, excitement, euphoria and altered senory perception. Effects in high doses include sedation, ataxia (trouble walking characterized by robotic leg movements - i.e. the robo-walk), slurred speech, strange utterances or random words, incoherent sentence structure, meaningless gibberish, aphasia (inability to speak), numbness, double vision, profoundly altered state of reality, loss of sensory perception (i.e. mind/body dissociation), complete loss of motor-ability (essentially equivalent to paralysis), out of body experiences, and time dilation. The author can attest to every one of these occurences (but rather with DXM) with the exception of out of body experience. Side effects of ketamine are similar to those of DXM and include hypertension, nausea & vomiting, hypersalivation, and respiratory depression/stimulation.
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