What is the appropriate emergency management for a 2‑year‑old child who ingested 2 mg of guanfacine (α2‑adrenergic agonist) and 1 mg of melatonin?

Emergency Management of Guanfacine and Melatonin Ingestion in a 2-Year-Old

This 2-year-old requires immediate emergency department evaluation with supportive care, continuous cardiorespiratory monitoring, and observation for at least 24 hours due to the risk of prolonged somnolence, bradycardia, and hypotension from guanfacine overdose. 1

Immediate Assessment and Monitoring

Establish continuous monitoring of vital signs, particularly heart rate and blood pressure, as guanfacine overdose characteristically causes drowsiness, lethargy, bradycardia, and hypotension. 1

• A documented case of a 2-year-old (12 kg) who ingested up to 4 mg of guanfacine developed lethargy with systolic blood pressure dropping to 58 mmHg and heart rate of 70 bpm at 16 hours post-ingestion, demonstrating that effects can be delayed and prolonged. 1
• Another pediatric case (6-year-old, 15 kg) who ingested guanfacine presented with prolonged somnolence and sinus bradycardia, confirming the typical toxidrome in young children. 2
• The 2 mg dose ingested by your patient represents 50% of the dose that caused significant symptoms in the documented 2-year-old case, warranting serious concern. 1

Gastrointestinal Decontamination

Perform gastric lavage followed by activated charcoal (1 g/kg) and sorbitol if the child presents within 2 hours of ingestion and is alert enough to protect their airway. 1

• The FDA label specifically documents that gastric lavage with activated charcoal and sorbitol successfully removed tablet fragments and prevented severe toxicity in the documented 2-year-old case. 1
• Do not induce emesis, as guanfacine's sedative effects may rapidly progress and compromise airway protection. 1

Supportive Care Protocol

Provide supportive therapy as the primary treatment, as guanfacine is not dialyzable (only 2.4% clearance). 1

Cardiovascular Management

• If bradycardia becomes symptomatic (heart rate <60 bpm with poor perfusion), consider isoproterenol infusion—a documented case used 0.8 mg over 12 hours successfully. 1
• Hypotension typically does not require intervention unless symptomatic; the documented 2-year-old with systolic pressure of 58 mmHg required no treatment and recovered fully. 1
• Avoid aggressive fluid resuscitation unless clearly hypovolemic, as alpha-2 agonist-induced hypotension is mediated centrally, not by volume depletion. 3

Neurological Monitoring

• Expect somnolence and lethargy as the primary manifestations; these are typically self-limited but can be prolonged (up to 24 hours). 1, 2
• Monitor for respiratory depression requiring mechanical ventilation, though this is rare—only 5 children required ventilation among 260,435 pediatric melatonin ingestions, and guanfacine alone rarely causes respiratory failure. 4

Melatonin Co-Ingestion Considerations

The 1 mg melatonin co-ingestion is unlikely to cause significant toxicity but may potentiate sedation from guanfacine. 4

• Pediatric melatonin ingestions are generally benign; among 260,435 cases reported over 10 years, serious outcomes were rare, with only 2 deaths (neither from isolated melatonin). 4
• The primary concern is additive sedation when combined with guanfacine's central alpha-2 agonist effects. 3, 4
• Melatonin does not cause cardiovascular depression, so bradycardia and hypotension are attributable solely to guanfacine. 4

Observation Period and Disposition

Admit for continuous cardiorespiratory monitoring for a minimum of 24 hours, as peak effects may be delayed up to 16 hours post-ingestion. 1

• The documented 2-year-old case showed nadir blood pressure at 16 hours, not immediately after ingestion. 1
• Discharge criteria include: normal vital signs for at least 6 hours, full alertness, ability to tolerate oral intake, and no cardiovascular instability. 1
• Guanfacine's mechanism as an alpha-2A adrenergic receptor agonist means effects are prolonged due to receptor binding kinetics. 3

Critical Pitfalls to Avoid

• Do not assume early normal vital signs indicate safety—cardiovascular depression can be delayed up to 16 hours. 1
• Do not administer naloxone—guanfacine toxicity is not opioid-mediated and naloxone will be ineffective. 3
• Do not attempt hemodialysis—guanfacine is only 2.4% dialyzable and will not expedite clearance. 1
• Do not discharge before 24 hours of observation unless the child remains completely asymptomatic with normal vital signs throughout. 1

Poison Control Consultation

Contact your regional poison control center (1-800-222-1222) for real-time guidance and to report the case to the National Poison Data System for surveillance purposes. 4