Nurses Compass
Drug Guide
Guanfacine Hydrochloride
Classification
Therapeutic: Antihypertensive; Attention Deficit Hyperactivity Disorder (ADHD) agent
Pharmacological: Alpha-2 adrenergic agonist
FDA Approved Indications
- Treatment of hypertension (Tenex)
- Management of ADHD (Intuniv)
Mechanism of Action
Guanfacine selectively stimulates alpha-2 adrenergic receptors in the central nervous system, reducing sympathetic nerve impulses, which results in decreased blood pressure and modulation of attention and behavior in ADHD.
Dosage and Administration
Adult: For hypertension: Starting dose 0.5 mg once daily, may be titrated up to 2 mg/day. For ADHD: Starting with 1 mg daily, titrate as needed up to 4 mg/day.
Pediatric: ADHD: 1 mg daily, adjustable based on response. Hypertension use is off-label.
Geriatric: Start at lower doses due to increased sensitivity and risk of side effects.
Renal Impairment: Adjust dosage based on severity; consult specific guidelines.
Hepatic Impairment: Use caution; no specific dose adjustment recommended, but monitor closely.
Pharmacokinetics
Absorption: Well absorbed orally.
Distribution: Extensively bound to plasma proteins.
Metabolism: Hepatic metabolism via conjugation and oxidation.
Excretion: Primarily in urine, with some fecal excretion.
Half Life: Approximately 17 hours, allowing for once-daily dosing.
Contraindications
- Known hypersensitivity to guanfacine or components.
Precautions
- Use with caution in patients with liver or kidney impairment.
- Monitor blood pressure closely, especially when initiating or adjusting doses.
- Avoid abrupt discontinuation to prevent rebound hypertension.
- Use cautiously in patients with cardiac conduction abnormalities.
Adverse Reactions - Common
- Sedation (Common)
- Dry mouth (Common)
- Fatigue (Common)
- Dizziness (Common)
Adverse Reactions - Serious
- Bradycardia (Less common)
- Hypotension (Less common)
- Rebound hypertension upon abrupt discontinuation (Rare)
Drug-Drug Interactions
- CNS depressants (additive sedation)
- Other antihypertensives (potentiation)
- MAO inhibitors (risk of hypertensive crisis)
Drug-Food Interactions
- No significant interactions reported
Drug-Herb Interactions
- Caution with sedative herbs (e.g., valerian, kava)
Nursing Implications
Assessment: Monitor blood pressure and heart rate regularly. Assess for side effects such as sedation or hypotension.
Diagnoses:
- Risk for falls related to orthostatic hypotension or sedation.
- Impaired skin integrity related to dry mouth and sedation.
Implementation: Administer doses as prescribed, preferably at bedtime to minimize sedation effects. Educate patients about rising slowly from sitting or lying positions.
Evaluation: Assess blood pressure and heart rate for effectiveness and adverse effects. Evaluate patient adherence and response.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Do not discontinue abruptly to avoid rebound hypertension.
- Notify healthcare provider if experiencing dizziness, fainting, or severe side effects.
- Limit activities requiring alertness until response is known.
Special Considerations
Black Box Warnings:
- Rebound hypertension can occur if medication is stopped abruptly.
Genetic Factors: No specific genetic considerations noted.
Lab Test Interference: May affect blood pressure readings; no interference with lab tests reported.
Overdose Management
Signs/Symptoms: Severe hypotension, bradycardia, drowsiness, lethargy.
Treatment: Supportive care, monitor vital signs, activated charcoal if ingestion recent, and vasopressors for significant hypotension. Gastric lavage may be considered in severe cases.
Storage and Handling
Storage: Store at room temperature, 20°C to 25°C (68°F to 77°F). keep away from moisture and light.
Stability: Stable under recommended storage conditions for at least 2 years.