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CARDIOVASCULAR SYSTEM › ANTIHYPERTENSIVES › ANTIADRENERGIC AGENTS, CENTRALLY ACTING › Imidazoline receptor agonists
guanfacine
C02AC02
Forms & Strengths
- Extended-release tablets: 1 mg, 2 mg, 3 mg, 4 mg
- Immediate-release tablets: 1 mg, 2 mg
Adult Dosing
- Hypertension (Immediate-release): 1 mg orally daily at bedtime; may increase gradually up to 3 mg daily in divided doses
- ADHD (Extended-release): Initial 1 mg orally once daily, adjusted in increments of no more than 1 mg/week to target range of 1 mg to 4 mg daily
Pediatric Dosing
- ADHD (Children 6-17 years, Extended-release): Initial 1 mg orally once daily, adjusted by max 1 mg/week to target range of 0.05 to 0.12 mg/kg/day (typically 1 mg to 4 mg daily based on weight)
Indications
- Attention deficit hyperactivity disorder (ADHD) as monotherapy or adjunctive therapy to stimulants (Extended-release)
- Hypertension (Immediate-release, off-label or older guidelines)
Mechanism of Action
- Central alpha-2A adrenergic receptor agonist
- Stimulates alpha-2A receptors in the prefrontal cortex, strengthening working memory, impulse control, and attention
- Reduces sympathetic outflow from the vasomotor center, decreasing heart rate and peripheral vascular resistance
Contraindications
- Hypersensitivity to guanfacine or any component of the formulation
Adverse Reactions
- Somnolence, sedation, and fatigue
- Hypotension and orthostatic hypotension
- Bradycardia
- Dry mouth
- Dizziness and headache
- Abdominal pain
Drug Interactions
- Strong CYP3A4 inhibitors (e.g., ketoconazole): May increase guanfacine plasma concentrations; reduce guanfacine dose by 50%
- Strong CYP3A4 inducers (e.g., rifampin): May decrease guanfacine plasma concentrations; consider increasing guanfacine dose up to double
- CNS depressants (e.g., alcohol, benzodiazepines, opioids): May enhance sedative effects
- Antihypertensive agents: May potentiate hypotensive effects leading to excessive blood pressure lowering
Curated Content: Needs Vetting Before Put to Clinical Use