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Ketamine
Updated 07/08
Type of Product
Parenteral general anaesthetic agent with analgesic properties, also prescribed orally for pain control. Illicit capsules for oral use are available, though the powder is generally snorted.
Synonyms
Cat valium, Kit-Kat, Special K, Super K, Vitamin K
Caution: using a slang term to try and identify a drug of abuse is potentially dangerous since there are many regional variations and the terms change over time.
Ingredients
Ketamine hydrochloride
Oral concentrate - 50 mg/5 mL (extemporaneously prepared from parenteral preparation, or available from a 'specials' manufacturer)
Injection - 10 mg/mL (20 mL vial), 100 mg/mL (10 mL vial).
Caution: the purity of street drugs may vary greatly.
Toxicity
Ketamine is a dissociative anaesthetic causing principally CNS and cardiac effects. Severity depends on ingested dose, often unknown as it is a "street" drug. When used therapeutically, its action is thought to be due to blocking neuronal excitation.
Deaths have been reported in adults following doses of 500-1000 mg when given intravenously (Long 2003, Licata 1994).
Ketamine has poor oral bioavailability with 17% of the dose absorbed compared to 93% when given intramuscularly (Clements, 1982). Onset of effects is likely to occur in a matter of seconds or minutes after injection, smoking and inhalation. Effects are shortlived following therapeutic dosing and depend on method of administration (5-10 min IV, up to 60 min nasal). The half-life is about 2.5 hours (Martindale).
ALERT BOX
All children who have been exposed to this drug
should be assessed by a physician.
Features
Onset of effects is rapid. However, effects are usually short-lived, typically 2-4 hours duration.
Mild:
An initial 'rush' with nausea, vomiting, slurred speech, blurred vision, numbness, dizziness and ataxia. An acute dystonic reaction has occurred in one case.
Moderate: Hypertension, tachycardia and agitation. Paralysis and muscle rigidity have been reported where the user cannot move or speak but is fully conscious and can see. An acute dystonic reaction has occurred in one case (Felser, 1982).
Agitated patients are at risk of other effects including hyperthermia, rhabdomyolysis, self-injury, enhanced perception, depersonalisation, movement disorders and confusion. During recovery, an 'emergence reaction' is often experienced. Features include floating sensations, vivid dreams, hypersensitivity to light, hallucinations and delirium.
Severe: Convulsions, polyneuropathy, raised intracranial pressure, pulmonary oedema, respiratory depression, aspiration (due to depression of the laryngeal reflexes), cardiac and respiratory arrest (Long 2003). Increased muscle tone and activity may produce hyperpyrexia.
Long-term effects:
Long term use may interfere with memory, learning and attention. Flashbacks have been described. (Jansen 1993). Chronic ketamine abuse has been complicated by lower urinary tract pathology including diminished functional bladder capacity with bladder muscle overactivity, acute renal failure with bilateral hydronephrosis possibly secondary to retroperitoneal fibrosis (Chu, 2007) and ulcerative cystitis (Shahani, 2007).
Management
1. Maintain a clear airway and adequate ventilation. In severe cases, endotracheal intubation may be required.
2. The benefit of gastric decontamination is uncertain. Consider activated charcoal (50 g for adults; 1 g/kg for children) if the patient presents within 1 hour of ingestion of any amount of the oral preparation
3. All patients should be observed for a minimum of 4 hours after exposure.
4. Monitor BP, pulse, temperature and respiratory rate and conscious level at least every 30 minutes for the first 2 hours.
5. Measure electrolytes and creatinine and creatine kinase and perform urine dipstick analysis in symptomatic patients.
6. Control agitation with oral or IV or rectal diazepam (0.1-0.3 mg/kg body weight). Larger doses may be required and repeat doses may be necessary.
Children under 3 years are easier to control without sedation. For children over 3 years 0.4 mg/kg orally is an appropriate dose for sedation.
7. Control convulsions with intravenous diazepam (10-20 mg in adults; 0.1-0.3 mg/kg body weight in children) or lorazepam (4 mg in adults; 0.05 mg/kg in children). Give oxygen and correct acid base and metabolic disturbances. Phenytoin (loading dose 15 mg/kg IV infusion in adults and children) may be useful if convulsions are unresponsive to above measures.
8.
Reassure patients with acute dystonic reactions. These usually respond to procyclidine (click here for doses). Diazepam (0.1-0.3 mg/kg body weight) is an alternative. Repeat doses may be required for prolonged reactions.
Note - acute dystonic reactions may occur up to 2-3 days after acute ingestion in a patient who is not normally receiving this drug. This is not a reason to keep patients in hospital but they should be warned that these occur very rarely and advised to return if they develop these symptoms.
9. If the CK is raised or rhabdomyolysis is suspected then there are theoretical reasons why volume replacement and urine alkalinization may be helpful in preventing or reducing the severity of rhabdomyolysis-induced renal failure. There is no strong evidence base from randomised controlled trials in poisoning but there is some evidence in crush injury. Give volume replacement and 225 mmol of 8.4% sodium bicarbonate over two hours to increase the urine pH >7. Haemodialysis or haemofiltration may be required for cases of acute renal failure or severe hyperkalaemia.
10. Mild hyperthermia should be treated with conventional cooling measures. However, when body temperature exceed 39-40 degrees centigrade aggressive cooling measures such as ice-baths and sedation (diazepam add agitation dose here) should be used.
If hyperthermia persists despite the above measures discuss with your local poisons information service: in the UK NPIS 0844 892 0111, in Ireland NPIC (01) 809 2566.
Click here for details you may be required to give when telephoning NPIS.
Dantrolene may be considered (1 mg/kg by rapid intravenous injection to a maximum of 10 mg/kg).
Consider other causes as hyperthermia may be caused by conditions other than poisoning.
11. If the systolic BP > 220 and/or diastolic > 140 mm Hg in adults in the absence of long-standing hypertension give diazepam (0.1 - 0.3 mg/kg body weight). Repeat doses may be necessary.
Persistent hypertension may respond to IV nitrates e.g. GTN starting at 1-2 mg/hour according to clinical response. Other antihypertensive agents may be effective but can be associated with adverse effects therefore:
If hypertension is unresponsive to the above measures discuss with your local poisons information service: in the UK NPIS 0844 892 0111, in Ireland NPIC (01) 809 2566.
Click here for details you may be required to give when telephoning NPIS.
In a child with hypertension:
Discuss with your local poisons information service: in the UK NPIS 0844 892 0111, in Ireland NPIC (01) 809 2566.
Click here for details you may be required to give when telephoning NPIS.
12.
Other measures as indicated by the patient's clinical condition.
13. On recovery warn patients about the possibility of "flashback" type reactions.
Links
Activated charcoal
Procyclidine doses
References
Updated 07/08
Type of Product
Parenteral general anaesthetic agent with analgesic properties, also prescribed orally for pain control. Illicit capsules for oral use are available, though the powder is generally snorted.
Synonyms
Cat valium, Kit-Kat, Special K, Super K, Vitamin K
Caution: using a slang term to try and identify a drug of abuse is potentially dangerous since there are many regional variations and the terms change over time.
Ingredients
Ketamine hydrochloride
Oral concentrate - 50 mg/5 mL (extemporaneously prepared from parenteral preparation, or available from a 'specials' manufacturer)
Injection - 10 mg/mL (20 mL vial), 100 mg/mL (10 mL vial).
Caution: the purity of street drugs may vary greatly.
Toxicity
Ketamine is a dissociative anaesthetic causing principally CNS and cardiac effects. Severity depends on ingested dose, often unknown as it is a "street" drug. When used therapeutically, its action is thought to be due to blocking neuronal excitation.
Deaths have been reported in adults following doses of 500-1000 mg when given intravenously (Long 2003, Licata 1994).
Ketamine has poor oral bioavailability with 17% of the dose absorbed compared to 93% when given intramuscularly (Clements, 1982). Onset of effects is likely to occur in a matter of seconds or minutes after injection, smoking and inhalation. Effects are shortlived following therapeutic dosing and depend on method of administration (5-10 min IV, up to 60 min nasal). The half-life is about 2.5 hours (Martindale).
ALERT BOX
All children who have been exposed to this drug
should be assessed by a physician.
Features
Onset of effects is rapid. However, effects are usually short-lived, typically 2-4 hours duration.
Mild:
An initial 'rush' with nausea, vomiting, slurred speech, blurred vision, numbness, dizziness and ataxia. An acute dystonic reaction has occurred in one case.
Moderate: Hypertension, tachycardia and agitation. Paralysis and muscle rigidity have been reported where the user cannot move or speak but is fully conscious and can see. An acute dystonic reaction has occurred in one case (Felser, 1982).
Agitated patients are at risk of other effects including hyperthermia, rhabdomyolysis, self-injury, enhanced perception, depersonalisation, movement disorders and confusion. During recovery, an 'emergence reaction' is often experienced. Features include floating sensations, vivid dreams, hypersensitivity to light, hallucinations and delirium.
Severe: Convulsions, polyneuropathy, raised intracranial pressure, pulmonary oedema, respiratory depression, aspiration (due to depression of the laryngeal reflexes), cardiac and respiratory arrest (Long 2003). Increased muscle tone and activity may produce hyperpyrexia.
Long-term effects:
Long term use may interfere with memory, learning and attention. Flashbacks have been described. (Jansen 1993). Chronic ketamine abuse has been complicated by lower urinary tract pathology including diminished functional bladder capacity with bladder muscle overactivity, acute renal failure with bilateral hydronephrosis possibly secondary to retroperitoneal fibrosis (Chu, 2007) and ulcerative cystitis (Shahani, 2007).
Management
1. Maintain a clear airway and adequate ventilation. In severe cases, endotracheal intubation may be required.
2. The benefit of gastric decontamination is uncertain. Consider activated charcoal (50 g for adults; 1 g/kg for children) if the patient presents within 1 hour of ingestion of any amount of the oral preparation
3. All patients should be observed for a minimum of 4 hours after exposure.
4. Monitor BP, pulse, temperature and respiratory rate and conscious level at least every 30 minutes for the first 2 hours.
5. Measure electrolytes and creatinine and creatine kinase and perform urine dipstick analysis in symptomatic patients.
6. Control agitation with oral or IV or rectal diazepam (0.1-0.3 mg/kg body weight). Larger doses may be required and repeat doses may be necessary.
Children under 3 years are easier to control without sedation. For children over 3 years 0.4 mg/kg orally is an appropriate dose for sedation.
7. Control convulsions with intravenous diazepam (10-20 mg in adults; 0.1-0.3 mg/kg body weight in children) or lorazepam (4 mg in adults; 0.05 mg/kg in children). Give oxygen and correct acid base and metabolic disturbances. Phenytoin (loading dose 15 mg/kg IV infusion in adults and children) may be useful if convulsions are unresponsive to above measures.
8.
Reassure patients with acute dystonic reactions. These usually respond to procyclidine (click here for doses). Diazepam (0.1-0.3 mg/kg body weight) is an alternative. Repeat doses may be required for prolonged reactions.
Note - acute dystonic reactions may occur up to 2-3 days after acute ingestion in a patient who is not normally receiving this drug. This is not a reason to keep patients in hospital but they should be warned that these occur very rarely and advised to return if they develop these symptoms.
9. If the CK is raised or rhabdomyolysis is suspected then there are theoretical reasons why volume replacement and urine alkalinization may be helpful in preventing or reducing the severity of rhabdomyolysis-induced renal failure. There is no strong evidence base from randomised controlled trials in poisoning but there is some evidence in crush injury. Give volume replacement and 225 mmol of 8.4% sodium bicarbonate over two hours to increase the urine pH >7. Haemodialysis or haemofiltration may be required for cases of acute renal failure or severe hyperkalaemia.
10. Mild hyperthermia should be treated with conventional cooling measures. However, when body temperature exceed 39-40 degrees centigrade aggressive cooling measures such as ice-baths and sedation (diazepam add agitation dose here) should be used.
If hyperthermia persists despite the above measures discuss with your local poisons information service: in the UK NPIS 0844 892 0111, in Ireland NPIC (01) 809 2566.
Click here for details you may be required to give when telephoning NPIS.
Dantrolene may be considered (1 mg/kg by rapid intravenous injection to a maximum of 10 mg/kg).
Consider other causes as hyperthermia may be caused by conditions other than poisoning.
11. If the systolic BP > 220 and/or diastolic > 140 mm Hg in adults in the absence of long-standing hypertension give diazepam (0.1 - 0.3 mg/kg body weight). Repeat doses may be necessary.
Persistent hypertension may respond to IV nitrates e.g. GTN starting at 1-2 mg/hour according to clinical response. Other antihypertensive agents may be effective but can be associated with adverse effects therefore:
If hypertension is unresponsive to the above measures discuss with your local poisons information service: in the UK NPIS 0844 892 0111, in Ireland NPIC (01) 809 2566.
Click here for details you may be required to give when telephoning NPIS.
In a child with hypertension:
Discuss with your local poisons information service: in the UK NPIS 0844 892 0111, in Ireland NPIC (01) 809 2566.
Click here for details you may be required to give when telephoning NPIS.
12.
Other measures as indicated by the patient's clinical condition.
13. On recovery warn patients about the possibility of "flashback" type reactions.
Links
Activated charcoal
Procyclidine doses
References
