Clonidine Overdose
The most likely medication ingested is clonidine, which characteristically produces the triad of CNS depression, profound bradycardia, and pinpoint pupils along with hypotension and hypothermia seen in this patient. 1, 2
Clinical Presentation Distinguishing Clonidine from Other Options
The combination of findings in this case—hypotension (85/55 mmHg), hypothermia (96°F), CNS depression with easy arousability, pinpoint pupils, and marked sinus bradycardia (45 bpm)—is pathognomonic for clonidine toxicity. 2, 3
Key distinguishing features:
Hydrocodone causes CNS depression and miosis but typically maintains normal or slightly elevated blood pressure, not the profound hypotension seen here, and produces less pronounced bradycardia. 1
Metoprolol causes bradycardia and hypotension but does not produce pinpoint pupils or significant CNS depression at typical overdose levels; patients remain alert or only mildly confused rather than sedated. 1
Digoxin causes bradycardia and hypotension but typically presents with nausea, confusion, and visual disturbances rather than sedation and miosis, and the ECG would likely show AV blocks or ventricular arrhythmias, not simple sinus bradycardia. 1
Pathophysiology
Clonidine overdose produces its clinical effects through excessive alpha-2 receptor stimulation in the brainstem, resulting in reduced sympathetic outflow that manifests as bradycardia and hypotension. 1 The CNS depression, miosis, and hypothermia complete the characteristic toxidrome. 2, 4
Clinical Course and Severity
Symptoms typically develop within 30 minutes to 2 hours after ingestion. 2 In adults, clonidine overdose causes persistent but generally not life-threatening effects, with most patients developing mild to moderate CNS depression and bradycardia lasting approximately 20 hours (median duration). 4 However, the frequency of CNS depression may be higher in children and adolescents, and as little as 0.1 mg has produced toxicity in pediatric patients. 2, 5
Immediate Management Algorithm
For hemodynamically significant bradycardia:
- Administer atropine sulfate 0.5-1.0 mg IV as first-line therapy. 1, 3, 6
- May repeat every 3-5 minutes to maximum dose of 3 mg. 7
For persistent hypotension unresponsive to atropine:
- Initiate intravenous fluid resuscitation. 3, 6
- If hypotension persists, start dopamine infusion at 5 mcg/kg/min, increasing by 5 mcg/kg/min every 2 minutes to maximum 20 mcg/kg/min. 7, 3
Gastrointestinal decontamination:
- Gastric lavage may be beneficial following recent and/or large ingestions. 2
- Administration of activated charcoal should be considered. 2, 3
- Induction of vomiting with ipecac is NOT recommended due to rapid development of CNS depression. 2
Important Caveats
Paradoxical hypertension may occur early in massive clonidine overdoses (typically >8,000 mcg) due to peripheral alpha-agonist effects, requiring cautious management. 1, 4, 6
Naloxone has been used as an adjunct for clonidine-induced respiratory depression, hypotension, and coma, but evidence of efficacy is limited—only 1 of 23 patients in one series showed documented improvement. 2, 4 Blood pressure must be monitored closely as naloxone administration has occasionally resulted in paradoxical hypertension. 2
Tolazoline (an alpha-blocker) has yielded inconsistent results and is not recommended as first-line therapy. 2
Mandatory Follow-up
Psychiatric evaluation is mandatory before discharge in cases of intentional clonidine ingestion in adolescents, with formal psychiatric clearance required for medical discharge. 1