Guanfacine (Intuniv for ADHD, Tenex for Hypertension) Dosage & Side Effects

What is guanfacine? What is guanfacine used for?

Guanfacine is an oral, centrally-acting alpha 2A adrenergic receptor agonist. It is available in two different formulations, Tenex immediate release tablets and Intuniv extended release tablets. Tenex is used alone or in combination with other medications for the treatment of hypertension (high blood pressure). Guanfacine reduces blood pressure by reducing the resistance of blood flow in the blood vessels, and by decreasing heart rate.

Intuniv (guanfacine extended release) is used alone or in combination with other medications for the treatment of attention deficit hyperactivity disorder (ADHD). The exact mechanism of action of guanfacine in ADHD is unknown. Extended release guanfacine is effective for the treatment of ADHD in children and adolescents between the ages of 6 to 17 in clinical trials lasting 8 weeks.

Guanfacine was approved by the US Food and Drug Administration (FDA) in 1986.

What brand names are available for guanfacine-oral?

Intuniv, Tenex

Is guanfacine-oral available as a generic drug?

Yes

Do I need a prescription for guanfacine-oral?

Yes

What are the side effects of guanfacine?

WARNING

Hypotension, bradycardia, and syncope

Use Intuniv with caution in patients at risk for hypotension, bradycardia, heart block, or syncope (e.g., those taking antihypertensives). Measure heart rate and blood pressure prior to initiation of therapy, following dose increases, and periodically while on therapy. Advise patients to avoid becoming dehydrated or overheated.

Sedation and somnolence occur commonly with Intuniv

Consider the potential for additive sedative effects with CNS depressant drugs. Caution patients against operating heavy equipment or driving until they know how they respond to Intuniv.

Common side effects

The most common side effects associated with guanfacine treatment are

• tiredness,
• sleepiness,
• trouble sleeping,
• nausea,
• low blood pressure,
• stomach pain, and
• dizziness.

Other important side effects that are rare, but serious, are:

• hair loss,
• memory impairment,
• heart failure,
• depression,
• seizures,
• skin problems,
• difficulty swallowing,
• edema,
• hallucinations,
• hypersensitivity or
• allergic
• reactions,
• mania,
• heart attack,
• rebound hypertension,
• kidney failure,
• rapid heartbeat, and
• visual disturbance.

Salt and sodium are the same.
See Answer

What is the dosage for guanfacine?

Recommended dose: 1 to 4 mg once daily in the morning or evening.

• Begin at a dose of 1 mg once daily and adjust in increments of no more than 1 mg/week.
• Do not crush, chew or break tablets before swallowing.
• Do not administer with high-fat meals, because of increased exposure.
• Do not substitute for immediate-release guanfacine tablets on a mg-per-mg basis, because of differing pharmacokinetic profiles.
• If switching from immediate-release guanfacine, discontinue that treatment and titrate with Intuniv as directed.
• Consider dosing on a mg/kg basis. Improvements observed starting at doses of 0.05-0.08 mg/kg once daily. Doses up to 0.12 mg/kg once daily may provide additional benefit (2.2).
• When discontinuing, taper the dose in decrements of no more than 1 mg every 3 to 7 days.

Which drugs or supplements interact with guanfacine?

: Rifampin and St. John's wort may reduce blood levels of guanfacine by increasing its metabolism (breakdown) in the intestine; doses of guanfacine may need to be increased when combined with drugs that reduce its blood levels.

Other drugs that also may reduce blood levels of guanfacine include carbamazepine (Tegretol, Tegretol XR , Equetro, Carbatrol, Epitol, Teril), phenytoin (Dilantin, Dilantin-125), phenobarbital, oxcarbazepine (Trileptal), rifabutin, rifampin, rifapentine, bosentan (Tracleer), and tipranavir/ritonavir (Aptivus).

Ketoconazole (Nizoral, Extina, Xolegel, Kuric), itraconazole (Sporanox), and simeprevir (Olysio) may increase blood levels of guanfacine by decreasing its metabolism in the intestine; the dose of guanfacine may need to be decreased when combined with drugs that increase its blood levels.

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Is guanfacine safe to take if I’m pregnant or breastfeeding?

It is not known whether guanfacine is excreted in breast milk. Due to the lack of safety data, guanfacine should be used cautiously in nursing mothers.

What else should I know about guanfacine?

What preparations of guanfacine-oral are available?

• Intuniv: Extended-Release Tablets: 1, 2, 3, and 4 mg
• Tenex: Immediate-Release Tablets: 1 and 2 mg

How should I keep guanfacine-oral stored?

Tablets should be stored at room temperature, between 15 C to 30 C (59 F to 86 F).