What are the treatment options for a Clonidine (Catapres) overdose?

Clonidine (Catapres) Overdose Management

Clonidine overdose requires primarily supportive care with focus on airway protection, cardiovascular monitoring, and symptom management—there is no specific antidote, though naloxone may provide partial benefit in select cases. 1

Clinical Presentation

Clonidine overdose produces a characteristic toxidrome with prominent CNS and cardiovascular effects:

CNS Effects:

• Depressed sensorium, drowsiness, and decreased reflexes are the hallmark features 2, 3
• Coma (GCS <9) occurs in approximately 5% of clonidine-alone overdoses and 12% when co-ingestants are involved 3
• Miosis occurs in 29% of cases 3
• Seizures, hypothermia, and irritability may occur 1

Cardiovascular Effects:

• Bradycardia occurs in 76% of cases, with median minimum heart rate of 48 bpm 3
• Bradycardia typically begins 2.5 hours post-ingestion and persists for a median of 20 hours 3
• Paradoxical hypertension may occur early (within 30 minutes to 2 hours), followed by hypotension 1, 2
• Hypotension develops in 24% of patients 3
• Reversible cardiac conduction defects or dysrhythmias may occur with large overdoses 1

Important caveat: As little as 0.1 mg has produced toxicity in children, making pediatric exposures particularly concerning 1

Initial Management

Gastrointestinal Decontamination:

• Do NOT induce vomiting with ipecac due to rapid onset of CNS depression 1
• Gastric lavage may be indicated for recent and/or large ingestions 1
• Activated charcoal administration is beneficial if given early 1

Supportive Care Algorithm:

1. Airway Management: Intubation is required in approximately 11% of cases, primarily when co-ingestants are involved 3

2. Bradycardia Treatment:

   • Atropine sulfate is first-line for symptomatic bradycardia 1
   • Monitor for prolonged bradycardia lasting up to 20 hours 3

3. Hypotension Management:

   • Intravenous fluids as initial therapy 1
   • Vasopressor agents if fluids are inadequate 1

4. Hypertension Management (if early paradoxical hypertension occurs):

   • Vasodilators may be used 1
   • This typically resolves spontaneously as hypotension develops

Role of Naloxone

Naloxone may be considered but has limited and inconsistent efficacy:

• It may provide benefit for respiratory depression, hypotension, and/or coma 1
• In one study of 23 patients receiving naloxone (median dose 2 mg), only one patient showed partial improvement in GCS 3
• Critical warning: Blood pressure must be monitored closely as naloxone has occasionally resulted in paradoxical hypertension 1
• Naloxone is not a definitive treatment and should not delay supportive care 3

Therapies NOT Recommended

• Tolazoline: Has yielded inconsistent results and is not recommended as first-line therapy 1
• Dialysis: Not likely to significantly enhance clonidine elimination 1

Monitoring and Disposition

Duration of Monitoring:

• Median length of stay is 21 hours (IQR: 14-35 hours) 3
• Bradycardia persists for a median of 20 hours 3
• Symptoms generally occur within 30 minutes to 2 hours after exposure 1

Prognosis:

• Clonidine overdose causes persistent but not life-threatening effects in adults 3
• No deaths occurred in a series of 108 adult overdoses 3
• Most patients develop only mild CNS depression and bradycardia 3
• Full recovery is expected with appropriate supportive care 1

Critical pitfall: The largest reported overdose (100 mg in an adult) resulted in severe toxicity including hypertension followed by hypotension, bradycardia, apnea, hallucinations, semicoma, and premature ventricular contractions, but the patient fully recovered with intensive treatment 1