Does Guanfacine Cause Increased Heart Rate?
No, guanfacine does not cause increased heart rate—it causes bradycardia (decreased heart rate), not tachycardia. 1, 2, 3
Cardiovascular Effects of Guanfacine
Guanfacine is an alpha-2A adrenergic receptor agonist that produces predictable cardiovascular depression, including:
- Bradycardia (slow heart rate) is a well-documented adverse effect, with heart rate reductions averaging 5 beats per minute in hemodynamic studies 3
- Hypotension (low blood pressure) occurs through decreased peripheral resistance 3
- Warnings specifically exist for hypotension/bradycardia and cardiac conduction abnormalities 1, 2
Clinical Evidence from FDA Labeling
The FDA drug label clearly lists bradycardia as an adverse cardiovascular effect, not tachycardia 3. In controlled trials:
- Bradycardia was reported as an adverse reaction in ≤3% of patients 3
- Palpitations occurred in ≤3% of patients 3
- Tachycardia is only mentioned in postmarketing surveillance as a rare, spontaneous report without definitive causation 3
The mechanism of action explains why tachycardia would be unexpected: guanfacine stimulates central alpha-2A receptors, which reduces sympathetic outflow, thereby lowering both blood pressure and heart rate 1, 3.
Important Clinical Caveats
When Tachycardia Might Occur
Rebound tachycardia can occur during withdrawal if guanfacine is abruptly discontinued rather than tapered 1, 4. This withdrawal syndrome:
- Occurs in approximately 3% of patients after prolonged treatment 4
- Is more likely in patients with very high baseline blood pressure, tendency to tachycardia, and doses exceeding 4 mg daily 4
- Requires tapering by 1 mg every 3-7 days to prevent rebound hypertension and tachycardia 1, 2
Monitoring Requirements
The American Academy of Pediatrics and American Heart Association recommend 1:
- Baseline blood pressure and heart rate measurement before initiation
- Monitoring during dose adjustments for bradycardia and hypotension
- Immediate contact with healthcare provider if experiencing very slow heart rate or irregular heartbeat 1
Rare Case Reports
One 2024 case report documented QT-interval prolongation with supratherapeutic guanfacine concentrations, but this involved bradycardia, not tachycardia 5. The patient had bradycardia and hypotension with a serum guanfacine level of 13.0 ng/mL (well above therapeutic range) 5.
Bottom Line
Guanfacine causes bradycardia and hypotension, not tachycardia, through its alpha-2A agonist mechanism that reduces sympathetic nervous system activity 1, 3, 6. The only scenario where increased heart rate occurs is during abrupt withdrawal, which is why proper tapering is mandatory 1, 4.