Kent R. Olson, MD
Many drugs and poisons can cause drowsiness, confusion or coma. (Table 1) Diagnosis may be aided by careful history and examination for a toxidrome.
It is essential to rule out other medical conditions that can cause altered mental status, such as acute head trauma, CNS infection (e.g., meningitis, encephalitis), metabolic derangements (e.g., hypoglycemia, hyponatremia, hypercalcemia, liver or kidney failure, etc.) Consider alcohol or sedative-hypnotic drug withdrawal in the patient with seizures or agitated delirium.
Management of coma is primarily supportive, with special attention to protection of the airway and endotracheal intubation, if necessary.
|Sample Drugs/Poisons Causing Coma||Common Clinical Features|
|Sedative-hypnotic drugs (benzodiazepines, barbiturates, etc.)||Coma with respiratory depression; decreased blood pressure; pupils small; hypothermia.|
|Opioids (heroin, morphine, codeine, hydrocodone, fentanyl, hydromorphone, etc)||Coma with marked respiratory depression; pupils often pinpoint; heroin users may have evidence of IV drug use.|
|Phenothiazines (chlorpromazine, thioridazine, promethazine, etc)||Alpha-adrenergic blockade typically causes hypotension with reflex tachycardia, small pupils.|
|Antihistamines and anticholinergics||Coma with tachycardia, dilated pupils, dry mucous membranes, urinary retention, ileus|
|Tricyclic antidepressants||Anticholinergic syndrome; seizures; QRS interval prolongation.|
|Organophosphates/carbamates||Syndrome of cholinergic excess: pinpoint pupils, hypersalivation and bronchorrhea, vomiting and diarrhea; muscle weakness.|
|Oral hypoglycemic agents (glyburide, glipizide, chlorpropamide, tolbutamide, etc.)||Coma due to hypoglycemia.|
|Cellular asphyxiants (cyanide, carbon monoxide, methemoglobinemia, hydrogen sulfide)||Metabolic acidosis (lactic acidosis); tachypnea, tachycardia common|
|Other antidepressants (fluoxetine, citalopram, sertraline, Bupropion, etc)||May be associated with serotonin syndrome (agitation, hyperreflexia and lower extremity clonus, hyperthermia)|
|Ethanol, other alcohols||Ethanol distinct breath odor; isopropyl alcohol metabolized to acetone; methanol and ethylene glycol to toxic organic acids (marked anion gap and osmolar gap)|
|Valproic acid||Small pupils; elevated serum ammonia; metabolic acidosis; mild transaminitis; hypocalcaemia.|
|Carbamazepine||Prolonged erratic absorption; nystagmus and ataxia; seizures at high doses; AV block.|