From the Guidelines
Treatment for guanfacine overdose requires immediate medical attention and typically involves supportive care focused on managing symptoms, particularly hypotension and bradycardia, as evidenced by the pharmacological effects of guanfacine as an alpha-2 adrenergic agonist 1. The management of guanfacine overdose is primarily focused on supportive care due to the lack of a specific antidote. Key considerations include:
- Monitoring vital signs, especially blood pressure and heart rate, as guanfacine can cause significant hypotension and bradycardia 1.
- Administering intravenous fluids to maintain blood pressure.
- Using vasopressors such as norepinephrine or phenylephrine for severe hypotension.
- Administering atropine for clinically significant bradycardia.
- Considering naloxone in cases of CNS and respiratory depression, although its efficacy for guanfacine overdose is not well-established. Given the long half-life of guanfacine and the potential for delayed symptoms, patients should be monitored for at least 24 hours 1. It is crucial to approach guanfacine overdose with caution, prioritizing the patient's hemodynamic stability and being prepared to manage potential complications, as the primary adverse effects of guanfacine include somnolence, dry mouth, dizziness, irritability, headache, bradycardia, hypotension, and abdominal pain 1.
From the FDA Drug Label
OVERDOSAGE Signs and Symptoms Drowsiness, lethargy, bradycardia and hypotension have been observed following overdose with guanfacine. A 25-year-old female intentionally ingested 60 mg. She presented with severe drowsiness and bradycardia of 45 beats/minute. Gastric lavage was performed and an infusion of isoproterenol (0. 8 mg in 12 hours) was administered. A 28-year-old female who ingested 30 - 40 mg developed only lethargy, was treated with activated charcoal and a cathartic, was monitored for 24 hours, and was discharged in good health. A 2-year-old male weighing 12 kg who ingested up to 4 mg of guanfacine developed lethargy Gastric lavage (followed by activated charcoal and sorbitol slurry via NG tube) removed some tablet fragments within 2 hours after ingestion, and vital signs were normal. During 24-hour observation in ICU, systolic pressure was 58 and heart rate 70 at 16 hours post-ingestion. No intervention was required, and child was discharged fully recovered the next day Treatment of Overdosage Gastric lavage and supportive therapy as appropriate. Guanfacine is not dialyzable in clinically significant amounts (2.4%).
The treatment for guanfacine overdose includes:
- Gastric lavage
- Supportive therapy as appropriate
- In some cases, activated charcoal and a cathartic may be used
- Monitoring of vital signs is necessary, and in severe cases, infusion of isoproterenol may be administered 2
From the Research
Treatment for Guanfacine Overdose
- Guanfacine overdose can cause symptoms ranging from mild sedation to coma, respiratory depression, hyporeflexia, hypotonia, bradycardia, and hypotension 3.
- Treatment may involve supportive care, such as intravenous fluids and vasopressors, to manage symptoms like hypotension and bradycardia 4.
- In some cases, naloxone has been used to treat guanfacine toxicity, with improvements in level of consciousness, blood pressure, and heart rate 5.
- Antihypertensive agents, such as nicardipine, may be necessary to manage hypertension in the initial stages of overdose 6.
- Prolonged monitoring is essential due to the potential for delayed onset of symptoms, including cardiogenic pulmonary edema and orthostatic hypotension 4, 7.
Management Considerations
- Emergency providers should be familiar with the toxidrome associated with guanfacine overdose and the importance of prolonged, close observation following ingestion 4.
- Patients may require mechanical ventilation and close monitoring of their cardiovascular status due to the risk of cardiac dysfunction and reduced cardiac contractility 4.
- The use of naloxone and other treatments should be considered on a case-by-case basis, taking into account the patient's symptoms and medical history 5.