Ketamine opioid

Drugs used recreationally - LSD, MDMA, phencyclidine, ketamine, cannabis, volatile solvents, opioids, cocaine, amphetamines, benzodiazepines, anticholinergics. 

The mechanisms of action of phencyclidine and ketamine are complex (Gorelick Balster, 1995). The drugs are non-competitive antagonists at NMDA receptors, and also bind to associated phencyclidine/sigma opioid receptors. They also have agonist actions at dopamine receptors, complex interactions with both nicotinic and muscarinic acetylcholine receptors and poorly understood interactions with noradrenergic and serotonergic systems. These multiple actions may combine to produce delirium and psychotic reactions. 

Emergence delirium with restlessness, disorientation and unpleasant dreams or hallucinations may occur for up 24 hours following ketamine administration. Their incidence is reduced by psychological preparation of the patient, avoidance of verbal and tactile stimulation during the recovery period, or by concomitant administration of opioids, benzodiazepines, propofol or physostigmine. However, unpleasant dreams may persist. 

The technique typically involves the use of intravenous midazolam for premedication (to provide anxiolysis, amnesia, and mild sedation) followed by a titrated, variable-rate propofol infusion (to provide moderate to deep levels of sedation), and a potent opioid analgesic or ketamine (to minimize the discomfort associated with the injection of local anesthesia and the surgical manipulations). 

Deep sedation is similar to a light state of general (intravenous) anesthesia involving decreased consciousness from which the patient is not easily aroused. Because deep sedation is often accompanied by a loss of protective reflexes, an inability to maintain a patent airway, and lack of verbal responsiveness to surgical stimuli, this state may be indistinguishable from intravenous anesthesia. Intravenous agents used in deep sedation protocols include the sedative-hypnotics thiopental, methohexital, midazolam, or propofol, the potent opioid analgesics, and ketamine. 

Fine, P. G. Low-dose ketamine in the management of opioid nonresponsive terminal cancer pain, J. Pain Symtom. Manage. 1999, 17, 296-300. 

Several drugs are used intravenously, alone or in combination with other drugs, to achieve an anesthetic state (as components of balanced anesthesia) or to sedate patients in intensive care units who must be mechanically ventilated. These drugs include the following (1) barbiturates (thiopental, methohexital) (2) benzodiazepines (midazolam, diazepam) (3) opioid analgesics (morphine, fentanyl, sufentanil, alfentanil, remifentanil) (4) propofol (5) ketamine and (6) miscellaneous drugs (droperidol, etomidate, dexmedetomidine). Figure 25-2 shows the structures of... 

Recovery is sufficiently rapid with many intravenous drugs to permit their extensive use for short ambulatory (outpatient) surgical procedures. In the case of propofol, recovery times are similar to those seen with the shortest-acting inhaled anesthetics. The anesthetic potency of intravenous anesthetics, including thiopental, ketamine, and propofol, is adequate to permit their use as the sole anesthetic in short surgical procedures when combined with nitrous oxide and opioid analgesics. 

Precautions. Ketamine should be used under the supervision of a clinician experienced in tracheal intubation, should this become necessary. Pulse and blood pressure must be monitored closely. Supplementary opioid analgesia is often required in surgical procedures causing visceral pain. 

---