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==Introduction==
'''Dissociative Anaesthetics''' interrupt signals from conciousness centers rather then a generalised center depression. The patients eyes remain open with a slow nystagmus, and hypertonus and spontaneous movements may occur. Examples include phencyclidine, ketamine and tiletamine.
'''Dissociative Anaesthetics''' interrupt signals from conciousness centers rather then a generalised center depression. The patients eyes remain open with a slow nystagmus, and hypertonus and spontaneous movements may occur. Examples include phencyclidine, ketamine and tiletamine.
==Mechanism of Action==
==Mechanism of Action==
Dissociative agents are highly lipid soluble, allowing for their rapid onset of action. They produce a dose related anaesthetic and analgesic effect. It is currently thought that the most likely mechanism of action is antagonism of the N-methyl-D-aspartate (NMDA) receptor. They appear to have a greater somatic analgesic effect compared with visceral pain.
Dissociative agents are highly lipid soluble, allowing for their rapid onset of action. They produce a dose related anaesthetic and analgesic effect. It is currently thought that the most likely mechanism of action is antagonism of the N-methyl-D-aspartate (NMDA) receptor. They appear to have a greater somatic analgesic effect compared with visceral pain. NMDA receptors in the CNS are receptors for exitatory amino acids, such as glutamate and aspartate. NMDA antagonists block the NMDA receptor and hence reduce CNS activity. However, they have no effect unless the excitatory transmitters are at work.
==Drugs in this Group==
==Drugs in this Group==
===Ketamine===
===Ketamine===
'''Ketamine''' is the most commonly used dissociative anaesthetic. It has the lowest potency and shortest duration of action of the three agents. It is available as a 10, 50 and 100mg/ml solution. It is often used in combination with [[Opioids|morphine]] and [[Local Anaesthetics|lidocaine]] in a continuous-rate infusion or ''MLK drip''.
'''Ketamine''' is an NMDA antagonist. It is given by constant rate infusion or as a bolus for intra-operative analgesia. Both visceral and somatic analgesia is provided, and the drug inhibits central sensitisation and therefore reduces long-term pain. Ketamine also has anaesthetic properties and is used to provide chemical restraint.
===Tiletamine===
===Tiletamine===
'''Tiletamine''' is available in combination with the [[#Benzodiazepines|benzodiazepine]], zolamzepam as a 1:1 combination in powder form which can be made into a highly concentrated solution used for darting wild animals.
'''Tiletamine''' is available in combination with the [[Benzodiazepines|benzodiazepine]], zolazepam as a 1:1 combination in powder form which can be made into a highly concentrated solution used for darting wild animals.
===Phencyclidine===
===Phencyclidine===