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Guanfacine

Medical Editor:

Brand Name: Intuniv, Tenex

Generic Name: Guanfacine

Drug Class: Alpha2 Adrenergic Agonists; ADHD Agents

What Is Guanfacine Used For?

Guanfacine is used to treat attention deficit hyperactivity disorder (ADHD), as part of a total treatment plan including psychological, educational, and social measures. Unlike other drugs used to treat ADHD, guanfacine is not a stimulant. The exact way that guanfacine works to treat ADHD is unknown. Guanfacine is thought to affect receptors in the parts of the brain that lead to strengthening working memory, reducing distraction, and improving attention and impulse control. Guanfacine may help lessen ADHD symptoms such as being disruptive, inattentive, hyperactive, impulsive, and arguing with adults or losing one's temper.

Guanfacine is also used to treat high blood pressure (hypertension) and is often given together with other blood pressure medications.

Guanfacine is available under the following different brand names: Intuniv, and Tenex.

Dosages of Guanfacine

Dosage Forms and Strengths

Tablet (Tenex)

  • 1mg
  • 2mg

Tablet, extended-release (Intuniv)

  • 1mg
  • 2mg
  • 3mg
  • 4mg

Dosage Considerations – Should be Given as Follows:

Hypertension

Adult

Tenex: 1 mg orally at bedtime; may increase to 2 mg after 3-4 weeks

Usual range 0.5-2 mg/day

Do not exceed 3 mg once/day due to increased risk of adverse effects

Pediatric

Children under 12 years

Safety and efficacy not established

Children 12 years and older

Tenex: 1 mg orally at bedtime; may increase to 2-3 mg after 3-4 weeks Usual range: 0.5-2 mg/day

Attention Deficit Hyperactivity Disorder, Pediatric

Intuniv: Monotherapy for ADHD or adjunct to stimulants

Children under 6 years: Safety and efficacy not established

Children 6-18 years

Intuniv: 1 mg/day orally initially; may adjust dose using increasing increments (not exceeding 1 mg/week) Take once daily, either in the morning or evening, at approximately the same time each day To balance the exposure-related potential benefits and risks, the recommended target dose range depending on clinical response and tolerability is 0.05-0.12 mg/kg/day orally initially  Aged 6-12 years: Doses greater than 4 mg/day not evaluated Aged 13-17 years: Doses greater than 7 mg/day not evaluated Adjunctive trials with psychostimulants: Doses greater than 4 mg/day not evaluated

Target dose range by weight

  • 25-33.9 kg: 2-3 mg/day
  • 34-41.4 kg: 2-4 mg/day
  • 41.5-49.4 kg: 3-5 mg/day
  • 49.5-58.4 kg: 3-6 mg/day
  • 58.5-91 kg: 4-7 mg/day
  • Greater than 91 kg: 5-7 mg/day

Heroin Withdrawal (Off-label)

0.03-1.75 mg/day orally for 5-15 days

Migraine Prophylaxis (Off-label)

Initial: 1 mg/day; do not exceed 3 mg/day

Dosage Modifications

Strong or moderate CYP3A4 inhibitors

Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations FDA-labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose; specific recommendations for immediate-release (IR) guanfacine are not available Starting therapy while currently taking CYP3A4 inhibitor: Decrease dose to half the recommended level Continuing therapy while adding CYP3A4 inhibitor: Decrease dose to half the recommended level Continuing therapy while stopping CYP3A4 inhibitor: Increase dose to recommended level

Strong or moderate CYP3A4 inducers

CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered Starting therapy while currently taking CYP3A4 inducer: Increase dose up to double the recommended level Continuing therapy while adding CYP3A4 inducer: Increase dose up to double the recommended level over 1-2 weeks Continuing therapy while stopping CYP3A4 inducer: Increase dose to recommended level

Dosing Considerations

Immediate-release and extended-release formulations are not interchangeable due to differences in bioavailability

What Are Side Effects Associated with Using Guanfacine?

Common side effects of guanfacine include:

Serious side effects of guanfacine include:

  • Severe dizziness
  • Slow heartbeat
  • Fainting
  • Mental/mood changes (such as depression, hallucinations, or thoughts of suicide)

Other side effects of guanfacine include:

Postmarketing side effects of guanfacine reported include:

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Guanfacine?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

Guanfacine has no known severe interactions with other drugs.

Serious Interactions of guanfacine include:

Guanfacine has moderate interactions with at least 127 different drugs.

Guanfacine has mild interactions with at least 46 different drugs.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Guanfacine?

Warnings

This medication contains guanfacine. Do not take Intuniv or Tenex if you are allergic to guanfacine or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.

Contraindications

Effects of Drug Abuse

  • Hypersensitivity

Short-Term Effects

  • See "What Are Side Effects Associated with Using Guanfacine?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Guanfacine?"

Cautions

Avoid abrupt withdrawal (can result in anxiety, nervousness, and rebound hypertension).

May cause low blood pressure (hypotension), orthostasis, slow heart rate (bradycardia), and fainting (syncope), use with caution in history of cerebrovascular disease, recent heart attack (myocardial infarction [MI]), severe coronary insufficiency, or syncope.

Chronic renal/hepatic failure.

May cause sedation, especially at start; avoid operating heavy machinery.

Skin rash with exfoliation reported.

Avoid concomitant use with other CNS depressants (e.g., alcohol) as they may potentiate central nervous system (CNS) effects.

Risk of cardiovascular effects may increase when administered concurrently with antihypertensive medications or drugs that affect heart rate.

ADHD

Low blood pressure (hypotension) is dose-limiting Do not substitute extended-release tablet for immediate-release guanfacine on a mg/mg basis, because of differing pharmacokinetic profiles May cause dose-dependent hypotension, bradycardia, and syncope Hallucinations reported in children with ADHD treated with guanfacine

Geriatric patients

May cause adverse CNS effects May cause bradycardia and orthostatic hypotension Not recommended as routine treatment for hypertension (Beers criteria)

Pregnancy and Lactation

Guanfacine may be acceptable for use during pregnancy. Either animal studies show no risk but human studies are not available or animal studies showed minor risks and human studies were done and showed no risk.

It is unknown if guanfacine is excreted into breast milk; use caution if breastfeeding.

Reviewed on 1/10/2018

SOURCE:
https://reference.medscape.com/drug/intuniv-tenex-guanfacine-342384
https://www.rxlist.com/intuniv-side-effects-drug-center.htm

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