Clonidine Overdose
The most likely medication ingested is clonidine, based on the classic triad of hypotension (85/55 mm Hg), bradycardia (45 bpm), and CNS depression with pinpoint pupils in this adolescent patient. 1
Clinical Presentation Distinguishing Clonidine from Other Options
Clonidine produces a distinctive toxidrome that includes CNS depression, bradycardia, hypotension, miosis (pinpoint pupils), hypothermia, and respiratory depression—all present in this case 1, 2. The combination of profound sedation that is easily arousable with tactile stimulation, marked bradycardia, and pinpoint pupils is pathognomonic for alpha-2 agonist toxicity 3, 4.
Why Not the Other Medications?
Hydrocodone would cause similar CNS depression and pinpoint pupils, but typically produces normal or slightly elevated blood pressure rather than hypotension, and bradycardia is less pronounced 5. The profound hypotension (85/55) and marked bradycardia (45 bpm) are more consistent with clonidine 1.
Metoprolol causes bradycardia and hypotension but does not produce pinpoint pupils or significant CNS depression at typical overdose levels 5, 6. Beta-blocker toxicity presents with alertness or mild confusion, not the sedation seen here 6.
Digoxin can cause bradycardia and hypotension, but typically presents with nausea, confusion, and visual disturbances (yellow-green halos) rather than sedation and miosis 5, 6. The ECG would likely show AV blocks or ventricular arrhythmias, not simple sinus bradycardia 5.
Pathophysiology of Clonidine Toxicity
Clonidine is a centrally-acting alpha-2 adrenergic agonist that reduces blood pressure through centrally mediated reduction in vasomotor tone 2. In overdose, it causes:
- CNS depression through excessive alpha-2 receptor stimulation in the brainstem 1, 4
- Bradycardia and hypotension from reduced sympathetic outflow 5, 1
- Miosis (pinpoint pupils) mimicking opioid toxicity 1, 7
- Hypothermia as seen in this patient (96°F) 1
The clinical effects typically occur within 30 minutes to 2 hours after ingestion, and as little as 0.1 mg can produce toxicity in children 1.
Critical Management Approach
Immediate Interventions
Supportive care is the cornerstone of treatment—there is no specific antidote for clonidine overdose 1, 2. Maintain airway patency and prepare for potential respiratory depression requiring bag-mask ventilation or intubation 1.
Atropine sulfate (0.5-1.0 mg IV) should be administered for hemodynamically significant bradycardia 5, 1, 2. This patient's heart rate of 45 bpm with hypotension warrants atropine 3.
Intravenous crystalloid fluids are first-line for hypotension 1, 2, 7. If hypotension persists despite adequate fluid resuscitation, dopamine infusion is recommended 2, 7.
Gastrointestinal Decontamination
Gastric lavage followed by activated charcoal may be beneficial if the patient presents within 1-2 hours of ingestion and can protect their airway 1, 2. Given this patient's CNS depression, airway protection must be ensured first 1.
Ipecac-induced vomiting is contraindicated due to the rapid development of CNS depression 1.
Monitoring and Disposition
Continuous cardiac monitoring and serial vital signs are essential, as clonidine's effects can last 24-48 hours 1, 3. Monitor for progression to respiratory depression, apnea, or seizures 1, 4.
ICU admission is warranted for this patient given the severity of bradycardia and hypotension 3, 7.
Common Pitfalls to Avoid
Do not confuse with pure opioid overdose: While both cause miosis and CNS depression, clonidine produces more profound hypotension and bradycardia 1, 7. Naloxone may be tried as a diagnostic/therapeutic adjunct for respiratory depression but is not definitive treatment 1.
Avoid alpha-adrenergic blocking agents (tolazoline) as first-line therapy—these have yielded inconsistent results and should only be considered if patients fail dopamine and IV fluids 1, 2.
Watch for paradoxical hypertension: In massive overdoses, clonidine's peripheral alpha-agonist effects may predominate early, causing transient hypertension before hypotension develops 5, 1, 7. This requires cautious management if it occurs 7, 8.
Psychiatric evaluation is mandatory before discharge, as this was an intentional ingestion in an adolescent 9. The patient cannot be medically discharged without formal psychiatric clearance 9.