A 32-year-old woman is brought to the emergency department by her husband due to slurred speech and difficulty walking. The patient has also been uncharacteristically drowsy for the past several hours. She has a history of bipolar disorder, insomnia, migraine headaches, seizures, and hypothyroidism. Temperature is 37 C (98.6 F), blood pressure is 110/70 mm Hg, pulse is 76/min, and respirations are 12/min. The patient is lethargic and falls asleep during the interview and physical examination. Pupils are 3 mm and reactive to light. The neck is supple and the oropharynx is clear. Chest auscultation is unremarkable. The abdomen is soft and nontender; bowel sounds are normal. Limited neurologic examination shows 2+ deep tendon reflexes in all 4 extremities; there is no Babinski sign, and strength is 5 on a scale of 0-5 throughout. No nystagmus or hand tremor is present. Blood glucose is 130 mg/dL. Which of the following is the most likely cause of this patient's symptoms?
Intoxication syndromes in drugs of abuse | |
Drug | Clinical features |
NMDA antagonists |
|
MDMA (ecstasy) |
|
Benzodiazepines |
|
Opioid narcotics |
|
MDMA = 3,4-methylenedioxymethamphetamine; | |
Benzodiazepines may be used in the management of bipolar disorder, insomnia, seizures, or alcohol withdrawal; however, risks of overdose and physical dependence/withdrawal make temporary use more desirable than chronic administration whenever possible. This patient's slurred speech, ataxia (ie, difficulty walking), and CNS depression (eg, lethargy, drowsiness) are consistent with benzodiazepine overdose.
Benzodiazepines are sedative-hypnotics with stereotypical features of intoxication:
CNS depression is the most common symptom in benzodiazepine overdose. Respiratory depression may also occur; however, this generally happens after large overdoses or rapid intravenous administration of short-acting formulations (eg, midazolam). Additionally, coingestion with other CNS depressants (eg, opioids, alcohol) greatly increases risk of respiratory depression and death.
(Choice B) Lithium toxicity can present with ataxia, lethargy, and slurred speech. However, gastrointestinal distress (eg, nausea, vomiting, diarrhea), nystagmus, tremor, and/or hyperreflexia would likely occur as well.
(Choice C) Opioid intoxication is likely to include sedation, ataxia, and slurred speech; however, respiratory depression and miosis (ie, pinpoint pupils) are expected as well. This patient's normal vital signs (eg, respiratory rate 12/min), bowel sounds, and pupillary reaction (reactive to light) and size (3 mm) are not expected in opioid overdose.
(Choice D) Ataxia, confusion, and CNS depression are likely in phenytoin overdose; however, nausea, vomiting, and nystagmus, not seen in this patient, would be expected as well.
(Choice E) Serotonin syndrome presents with hypertension, tachycardia, hyperreflexia, clonus, and agitation in the setting of excessive serotonergic drug use (eg, high-dose tricyclic antidepressant plus selective serotonin reuptake inhibitor). This patient's normal vital signs as well as deep tendon reflexes and absent agitation are inconsistent with serotonin syndrome.
Educational objective:
Slurred speech, unsteady gait, and lethargy are concerning signs of benzodiazepine intoxication. Benzodiazepine overdose can be distinguished from opioid overdose, as severe hypoventilation, hypoactive bowel sounds, and pupillary constriction are more likely to be seen with opioid overdose.