Guanfacine

Drug Overview

Guanfacine is a selective α_2A-adrenergic receptor agonist primarily used to treat Attention Deficit Hyperactivity Disorder (ADHD) and hypertension. Its mechanism of action involves activating α_2A receptors in specific brain neurons, regulating sympathetic nervous activity, thereby stabilizing blood pressure and improving concentration issues.

This medication has central antihypertensive effects, reducing blood pressure fluctuations and exerting a weaker vasoconstrictive effect on peripheral blood vessels, thus posing a lower risk of hypotension. In ADHD treatment, guanfacine can enhance focus and reduce impulsivity, making it an important non-stimulant alternative to stimulant medications.

Brand Names and Generic Name

The generic name is Guanfacine, with main brand names including:

• Tenex: used for hypertension
• Intuniv: specifically for children and adolescents with ADHD

Drug Classification

Guanfacine is classified as an α-2 adrenergic receptor agonist, belonging to the class of sympathetic nervous system suppressants. Its pharmacological action differs from traditional β-blockers, primarily acting on the central nervous system with a weaker effect on peripheral vascular smooth muscle, resulting in a more stable antihypertensive effect.

In terms of therapeutic classification, it is categorized as a non-stimulant for ADHD, with a different mechanism of action from stimulant drugs like methylphenidate, suitable for patients intolerant to stimulants.

Indications

Main indications include:

• Hypertension: used alone or in combination with other antihypertensive agents to control blood pressure
• Attention Deficit Hyperactivity Disorder (ADHD): suitable for managing symptoms in children over 6 years old and adolescents

Clinically, Intuniv is specifically designed for ADHD, with dosage adjustments based on age and weight. For hypertension, it is usually administered once daily with regular blood pressure monitoring.

Common Side Effects

Common mild side effects include:

• Dizziness or headache
• Dry mouth

Serious side effects may include:

• Hypotension (low blood pressure, which may cause dizziness or fainting)
• Bradycardia
• Mood or behavioral changes (especially in ADHD treatment)

Warnings and Precautions

Contraindications: Patients allergic to guanfacine or its components should not use. Those with severe bradycardia, sick sinus syndrome, or second-degree or higher atrioventricular block should avoid use.

Pregnancy and Lactation: Pregnancy category C indicates potential risks to the fetus; benefits and risks should be evaluated in pregnant or planning pregnancy. It may be excreted into breast milk, so caution is advised during breastfeeding.

Drug Interactions

Concurrent use with the following medications may enhance antihypertensive effects:

• Other antihypertensive drugs (e.g., ACE inhibitors, diuretics)
• β-blockers (e.g., metoprolol)

Avoid combining with peripheral α-adrenergic antagonists (e.g., doxazosin), as this may cause severe hypotension. When using SSRIs, blood pressure should be monitored.

Dosage and Administration

Hypertension treatment:

• Initial dose typically 1 mg daily, titrated up to 2-4 mg weekly
• Should be combined with a low-sodium diet and lifestyle modifications

ADHD treatment:

• Children start at 0.1 mg daily, titrated weekly to 0.2-0.4 mg
• Recommended to take in the morning to avoid sleep disturbances

Missed Dose Management

If a dose is missed, it should be taken as soon as remembered, but if the next dose is due within 6 hours, skip the missed dose and resume normal schedule the next day. Do not double the dose to reduce the risk of hypotension.

Overdose Management

Overdose may cause severe hypotension and bradycardia; immediate medical attention is required. Symptoms include confusion, fainting, and difficulty breathing. Patients should be taken to the emergency room for blood pressure support and monitoring of symptoms.

 

Frequently Asked Questions

Is it necessary to take Guanfacine with specific meal timings?

It is recommended to take it at the same time each day, either before or after meals. If gastrointestinal discomfort occurs, taking it with food may help alleviate symptoms. Avoid concurrent intake with high-fat meals, as this may prolong the onset of action.

How should I respond to side effects like dizziness or headache?

Initial mild dizziness or headache is common and usually diminishes as the body adjusts. Try to change positions slowly (e.g., sit for 1 minute before standing) and maintain regular routines. If symptoms persist beyond two weeks or worsen, consult a physician for dose adjustment.

What precautions should be taken when combining with other antihypertensive drugs?

Combining with other antihypertensives (e.g., β-blockers, diuretics) may enhance blood pressure reduction; blood pressure should be monitored regularly. The physician will adjust doses based on blood pressure readings. Patients should not alter doses independently to avoid hypotensive crises.

Does long-term use of Guanfacine affect liver or kidney function?

Current clinical studies suggest that at prescribed doses, long-term effects on liver and kidney function are minimal. Patients with chronic kidney or liver disease should have regular tests. If unexplained fatigue, jaundice, or edema occurs, discontinue medication and seek medical attention.

Can Guanfacine be used during pregnancy or breastfeeding?

Use during pregnancy should be cautious; there is limited clinical data on safety. During breastfeeding, it should be avoided as the drug may pass into breast milk. If planning pregnancy or currently breastfeeding, inform your doctor in advance to evaluate alternative treatments.