How should a suspected moxonidine overdose in a child or adolescent be managed?

Management of Moxonidine Overdose in Pediatric Patients

Immediately contact a Poison Control Center and provide supportive care focused on airway, breathing, and cardiovascular monitoring, as there is no specific antidote for moxonidine toxicity. 1

Immediate Actions and Assessment

• Activate emergency medical services and contact Poison Control immediately upon suspicion of moxonidine ingestion, as recommended by the FDA drug label for all pediatric overdoses. 1
• Assess and secure the airway as the absolute first priority, ensuring adequate oxygenation and ventilation before any other intervention. 2
• Monitor vital signs continuously, with particular attention to blood pressure (expect hypotension), heart rate (expect bradycardia), and level of consciousness (expect CNS depression). 3, 4, 5

Expected Clinical Manifestations

Moxonidine is a centrally-acting antihypertensive that stimulates imidazoline I₁-receptors and α₂-adrenoceptors, leading to predictable toxicity:

• Profound hypotension due to decreased systemic vascular resistance is the primary life-threatening effect. 3, 5
• Bradycardia may occur, though cardiac output may be preserved initially. 3, 5
• Central nervous system depression ranging from drowsiness to coma, similar to other centrally-acting agents. 6, 4
• Dry mouth and sedation are common even at therapeutic doses and will be exaggerated in overdose. 6, 3

Supportive Management (No Specific Antidote Exists)

Cardiovascular Support

• Administer intravenous isotonic crystalloid boluses (20 mL/kg in children) for hypotension as the first-line intervention. 2
• Consider vasopressor support if hypotension persists despite adequate fluid resuscitation, though specific evidence for moxonidine overdose is lacking.
• Atropine may be considered for symptomatic bradycardia (0.02 mg/kg in children), though its efficacy in moxonidine-induced bradycardia is not established. 7

Respiratory Support

• Provide supplemental oxygen for any patient with altered mental status or respiratory compromise. 2, 8
• Initiate bag-mask ventilation or intubation if respiratory depression is severe or the patient cannot protect their airway. 2
• Continue ventilatory support until spontaneous adequate breathing returns, as the duration of CNS depression may be prolonged. 2

Gastrointestinal Decontamination

• Activated charcoal may be considered if the patient presents within 1 hour of ingestion and can protect their airway or is intubated, though specific evidence for moxonidine is lacking.
• Do not induce vomiting in any pediatric overdose due to risk of aspiration, particularly given the CNS depressant effects of moxonidine. 9

Observation and Monitoring Duration

• Observe all symptomatic patients for a minimum of 6–8 hours after ingestion, as moxonidine has a half-life of 2.5 hours but its antihypertensive effects persist longer than predicted by pharmacokinetics, suggesting CNS retention. 3, 4, 5
• Extend observation to 12–24 hours if the patient remains symptomatic, has ingested a large dose, or has renal impairment (which prolongs moxonidine elimination). 3, 4
• Monitor for recurrence of symptoms even after initial improvement, as redistribution or delayed absorption may occur. 2

Critical Pitfalls to Avoid

• Do not assume naloxone will reverse moxonidine toxicity—moxonidine is not an opioid and naloxone is ineffective for imidazoline receptor agonists. 2, 8
• Do not delay emergency activation while attempting home observation or waiting to see if symptoms develop. 2, 1
• Do not overlook co-ingestions, particularly benzodiazepines or other CNS depressants, which may potentiate sedation and respiratory depression. 7, 6
• Do not discharge asymptomatic patients prematurely—the prolonged CNS retention of moxonidine means delayed toxicity is possible. 3, 4, 5

Special Considerations in Pediatric Patients

• Children may be more susceptible to CNS depression from centrally-acting agents, requiring lower thresholds for respiratory support. 7, 9
• Renal function affects elimination—if renal impairment is present or suspected, anticipate prolonged toxicity and extended monitoring. 3, 4
• Provide caregiver education about safe medication storage to prevent future exposures, as childhood drug overdoses are highly preventable. 9