From the FDA Drug Label
OVERDOSAGE Signs and Symptoms Drowsiness, lethargy, bradycardia and hypotension have been observed following overdose with guanfacine. Too much guanfacine can cause:
- Drowsiness
- Lethargy
- Bradycardia (slow heart rate)
- Hypotension (low blood pressure) 1
From the Research
Too much guanfacine can cause severe side effects, including low blood pressure, bradycardia, excessive sedation, and respiratory depression, as reported in a recent case study published in 2022 2.
Overview of Guanfacine Overdose
Guanfacine is a selective alpha-2a adrenoreceptor agonist that can cause symptoms ranging from mild sedation to coma, respiratory depression, hyporeflexia, hypotonia, bradycardia, and hypotension in cases of overdose. The effects of guanfacine overdose can vary based on multiple factors, including age, quantity ingested, organ functions, coingestions, time since ingestion, and specific dosage form.
Common Symptoms of Overdose
Some common symptoms of guanfacine overdose include:
- Low blood pressure (hypotension), which may lead to dizziness, lightheadedness, or fainting, especially when standing up
- Bradycardia (slow heart rate), potentially causing weakness or fatigue
- Excessive sedation or drowsiness, making it difficult to stay awake or function normally
- Dry mouth, irritability, lethargy, and in severe cases, respiratory depression
- Confusion, headaches, and gastrointestinal issues like nausea or vomiting
Importance of Immediate Medical Attention
If guanfacine overdose is suspected, immediate medical attention is necessary, as reported in a case study published in 2025 3. Monitoring and supportive care may be required until the medication clears from the system. Guanfacine overdose can also cause cardiogenic pulmonary edema, as reported in a case study published in 2021 4.
Recent Studies on Guanfacine
Recent studies, such as a systematic review and meta-analysis published in 2023 5, have shown that guanfacine is safe and effective for treating attention-deficit hyperactivity disorder (ADHD). However, the most recent and highest-quality study, a case report published in 2022 2, highlights the importance of recognizing the potential for severe side effects, including low blood pressure, bradycardia, and respiratory depression, in cases of guanfacine overdose.
Clinical Implications
In clinical practice, it is essential to prioritize the single most recent and highest-quality study, which in this case is the 2022 case report 2. This study highlights the potential for severe side effects and the importance of immediate medical attention in cases of guanfacine overdose. By prioritizing this study, clinicians can provide the best possible care for patients who have overdosed on guanfacine.