From the Guidelines
Guanfacine can cause hypotension as a side effect, and management involves careful monitoring and dose adjustments. According to the most recent evidence from 1, it is essential to test for orthostatic hypotension before starting or intensifying blood pressure-lowering medication. Guanfacine, a centrally-acting alpha-2 adrenergic agonist, reduces sympathetic outflow from the brain, decreasing peripheral vascular resistance and heart rate, which can lead to hypotension 1.
Some key points to consider when managing hypotension caused by guanfacine include:
- Assessing the severity of symptoms
- Continuing monitoring without immediate intervention for mild asymptomatic hypotension
- Reducing the guanfacine dose by 0.5-1 mg or extending the dosing interval for moderate hypotension with mild symptoms
- Temporarily discontinuing guanfacine and seeking medical attention for severe hypotension with significant symptoms like dizziness or syncope
- Tapering the medication over 3-7 days when discontinuation is necessary to avoid rebound hypertension
Risk factors for hypotension caused by guanfacine include concurrent use of other antihypertensives, dehydration, and underlying cardiovascular conditions 1. Preventive measures include starting with low doses (0.5-1 mg daily), gradual titration, taking the medication at bedtime to minimize daytime hypotension, maintaining adequate hydration, and regular blood pressure monitoring, especially during dose adjustments 1.
It is crucial to prioritize the patient's safety and adjust the treatment plan accordingly, considering the potential risks and benefits of guanfacine therapy, as recommended by the most recent guidelines 1.
From the FDA Drug Label
Drowsiness, lethargy, bradycardia and hypotension have been observed following overdose with guanfacine. The relationship between hypotension and guanfacine (Tenex) is that hypotension is a potential effect of the drug, particularly in cases of overdose. Guanfacine can cause a decrease in blood pressure, and severe hypotension has been observed in some cases of overdose 2.
- Key points:
- Guanfacine can cause hypotension as a side effect
- Overdose can lead to severe hypotension
- Guanfacine is not dialyzable in clinically significant amounts
- Treatment of overdose includes gastric lavage and supportive therapy as appropriate 2
From the Research
Relationship Between Hypotension and Guanfacine (Tenex)
- Guanfacine is an alpha-two agonist that can cause hypotension, particularly when taken in incorrect formulations or doses 3.
- The drug is commonly used to treat attention-deficit hyperactivity disorder (ADHD) in the pediatric population and hypertension in the adult population 3.
- In cases of overdose, guanfacine can cause a mixed clinical syndrome, with initial effects including drowsiness, lethargy, dry mouth, and diaphoresis, and cardiovascular effects that may present as hypotension or hypertension 4.
- The management of guanfacine overdose is largely supportive, with a focus on support of blood pressure 4.
- Guanfacine has been shown to be effective in reducing blood pressure in patients with essential hypertension, with a mechanism of action similar to that of clonidine 5, 6.
- Withdrawal of guanfacine after long-term treatment can lead to a gradual recovery of blood pressure over 2-4 days, without significant symptoms or biochemical evidence of catecholamine excess 7.
Clinical Presentation and Management
- The clinical presentation of guanfacine overdose may include hypotension, bradycardia, and lethargy, and may require admission to the pediatric intensive care unit (PICU) due to hemodynamic instability 3.
- The management of guanfacine overdose is largely supportive, with a focus on sedation, control of dyskinesias, and support of blood pressure 4.
- Guanfacine can cause dry mouth and sedation, particularly at higher doses, but these side effects are generally less frequent than with other centrally acting antihypertensives 5, 6.
Pharmacology and Pharmacokinetics
- Guanfacine is a centrally acting alpha-adrenoceptor agonist with a relatively long elimination half-life, allowing for once-daily dosing 5.
- The drug reduces blood pressure by decreasing sympathetic outflow from the central nervous system, and has been shown to be effective in reducing plasma noradrenaline and urinary catecholamine excretion 5, 7.