This article is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Never start, stop, or change medication without consulting your prescribing physician. No pharmaceutical sponsorship. No affiliate links.
Guanfacine extended-release (brand name Intuniv, also sold as generic guanfacine ER) is a non-stimulant ADHD medication that acts on alpha-2A adrenergic receptors. It is FDA-approved for ADHD in children and teens 6 to 17, on its own or added to a stimulant; use in adults is off-label in the US. The most common side effects are sleepiness, tiredness, and lower blood pressure, and it must be tapered rather than stopped suddenly because abrupt discontinuation can cause rebound high blood pressure.
What is guanfacine and how does it treat ADHD?
Guanfacine is a central alpha-2A adrenergic receptor agonist. It was first used as a blood pressure medication, and the immediate-release tablet is still labeled only for hypertension. The extended-release version, Intuniv, is labeled for ADHD.
The Intuniv label states plainly that "the mechanism of action of guanfacine in ADHD is not known." The leading explanation is that stimulating alpha-2A receptors in the prefrontal cortex strengthens the signaling that supports working memory and impulse control, but that is a hypothesis rather than an established fact. What is established is that guanfacine is not a stimulant and, per the label, "is not a controlled substance and has no known potential for abuse or dependence."
That last point is practical: guanfacine ER prescriptions can include refills and are not subject to the special federal rules that apply to Schedule II stimulants.
Who is Intuniv approved for?
The Intuniv label indicates it for ADHD as monotherapy and as add-on therapy to stimulant medications. Its efficacy was established in children and adolescents aged 6 to 17, and the label says safety and efficacy in children under 6 have not been established.
Adults: guanfacine ER is not FDA-approved for adult ADHD, so adult use in the US is off-label. Prescribers do sometimes use it off-label, and there is trial evidence: a randomized, placebo-controlled phase 3 study in 201 Japanese adults with ADHD found guanfacine ER (4–6 mg/day) improved symptom scores more than placebo, with an effect size of 0.52 (Iwanami et al., 2020). In that trial, 19.8% of adults on guanfacine stopped because of side effects, compared with 3.0% on placebo, so tolerability is a real consideration.
Extended-release vs. immediate-release guanfacine: what is the difference?
| Guanfacine ER (Intuniv and generics) | Guanfacine IR (generic tablets) | |
|---|---|---|
| FDA-labeled use | ADHD, ages 6–17 (alone or with a stimulant) | High blood pressure |
| Blood levels at the same dose | About 60% lower peak and 43% lower total exposure than IR, with a peak about 3 hours later | Higher, faster peak |
| Interchangeable mg for mg? | No | No |
The label is explicit: do not substitute the two on a milligram-for-milligram basis. If you are switching from immediate-release guanfacine, the IR product is stopped and Intuniv is titrated using its own schedule. If your pharmacy fills a different product than you expected, ask before taking it.
How is Intuniv dosed?
From the FDA label:
- Start: 1 mg once daily, morning or evening, at about the same time each day.
- Increase: by no more than 1 mg per week.
- Target range: 0.05 to 0.12 mg/kg/day (1 to 7 mg/day total), adjusted by response and tolerability.
- Limits studied: doses above 4 mg/day were not evaluated in children 6 to 12; doses above 7 mg/day were not evaluated in adolescents 13 to 17; doses above 4 mg/day were not studied when added to a stimulant.
- How to take it: swallow whole. Do not crush, chew, or break the tablet.
- Avoid high-fat meals at dosing time. A high-fat breakfast raised peak blood levels by about 75% and overall exposure by about 40% compared with taking it fasting. That spike can mean more drowsiness and lower blood pressure. See our guide to ADHD medication and food for meal-timing strategies.
Unlike stimulants, guanfacine is not felt within hours. Because dosing starts low and rises by at most 1 mg a week, it often takes several weeks to reach a target dose and judge whether it is working. Your prescriber should set expectations about when to reassess.
What are the side effects of guanfacine?
The label lists the most common adverse reactions (at least 5% and at least twice the placebo rate) in short-term pediatric trials:
| Side effect | Intuniv alone vs. placebo | Intuniv + stimulant vs. placebo + stimulant |
|---|---|---|
| Somnolence (sleepiness) | 38% vs. 11% | 18% vs. 7% |
| Fatigue | 14% vs. 3% | 10% vs. 3% |
| Hypotension (low blood pressure) | 7% vs. 3% | — |
| Dizziness | 6% vs. 4% | 8% vs. 4% |
| Nausea | 6% vs. 2% | 5% vs. 3% |
| Lethargy | 6% vs. 3% | — |
| Insomnia | — | 12% vs. 6% |
| Abdominal pain | — | 10% vs. 3% |
| Decreased appetite | — | 7% vs. 4% |
A dash means the reaction did not meet the label's threshold for that group, not that it never happened. Sleepiness is by far the most common complaint and is the main reason some people take guanfacine in the evening.
Blood pressure and heart rate go down. Across the two main fixed-dose monotherapy studies, the largest average changes were about −5.4 mmHg systolic, −3.4 mmHg diastolic, and −5.5 beats per minute; at 4 mg they were larger (−8.2 mmHg, −5.4 mmHg, and −8.6 bpm). Fainting (syncope) occurred in 1% of pediatric patients in the clinical program. The label advises slow titration, monitoring of heart rate and blood pressure, and avoiding dehydration and overheating.
Call your prescriber about lightheadedness, unusual tiredness, or a slow pulse. Call 911 for fainting with injury, chest pain, severe shortness of breath, or a very slow heartbeat with confusion.
Why you should never stop guanfacine suddenly
This is the single most important safety point about guanfacine. The label warns that abrupt discontinuation can cause clinically significant and persistent rebound hypertension, and hypertensive encephalopathy (a dangerous blood pressure emergency affecting the brain) has been reported. Concurrent stimulant use may increase that risk.
When stopping, the label calls for tapering the total daily dose by no more than 1 mg every 3 to 7 days, with blood pressure and pulse monitoring. That means:
- Do not stop on your own because a refill is late, you are traveling, or you feel it is not working. Talk to your prescriber about a taper plan.
- Missed doses matter too. Do not double up. The patient information says that if you miss 2 or more doses, talk to your doctor, because you may need to restart at a lower dose.
- Severe headache, confusion, vision changes, or chest pain after stopping guanfacine need emergency care: call 911.
What drugs and substances interact with guanfacine?
- CYP3A4 inhibitors (for example ketoconazole or fluconazole) raise guanfacine levels. The label says to reduce the Intuniv dose to half when a strong or moderate inhibitor is used.
- CYP3A4 inducers (for example carbamazepine or rifampin) lower guanfacine levels. The label allows up to double the usual dose, adjusted over 1 to 2 weeks.
- Alcohol, sedatives, and other CNS depressants can add to sleepiness. The label advises avoiding alcohol and not driving or operating heavy equipment until you know how guanfacine affects you.
- Other blood-pressure-lowering or heart-rate-lowering drugs can add to hypotension, bradycardia, and fainting risk.
Give your prescriber and pharmacist a complete list of medicines and supplements, and ask before starting anything new.
Guanfacine on its own vs. added to a stimulant
Intuniv is one of the few non-stimulants specifically labeled for use alongside a stimulant. In practice, prescribers often consider it when a stimulant helps attention but evening symptoms, irritability, or sleep remain a problem, or when a stimulant cannot be raised further because of side effects. As a standalone option, it is often considered when stimulants are not tolerated or a non-controlled medication is preferred. For a side-by-side view of the other non-stimulants, see our non-stimulant guide and stimulant vs. non-stimulant comparison.
Frequently asked questions
Is guanfacine a stimulant?
No. Guanfacine is a central alpha-2A adrenergic agonist. The Intuniv label states it is not a controlled substance and has no known potential for abuse or dependence.
Is Intuniv approved for adults?
No. Intuniv is FDA-approved for ADHD in children and adolescents 6 to 17. Prescribing it to adults in the US is off-label, although placebo-controlled trials in adults have been published.
How long does guanfacine take to work for ADHD?
Dosing starts at 1 mg and rises by no more than 1 mg per week, so it usually takes several weeks to reach a target dose and judge the effect. Ask your prescriber when you should reassess.
Can I stop taking guanfacine suddenly?
No. Stopping abruptly can cause rebound high blood pressure. The label calls for tapering by no more than 1 mg every 3 to 7 days under your prescriber’s guidance.
Should I take Intuniv with food?
You can take it with or without food, but not with a high-fat meal. A high-fat meal raised peak levels by about 75% and total exposure by about 40%.
Are guanfacine ER and guanfacine IR the same?
No. The immediate-release tablet is labeled for high blood pressure, while the extended-release form is labeled for ADHD. They are not interchangeable milligram for milligram.
References
- Takeda / DailyMed. INTUNIV (guanfacine) extended-release tablets, Prescribing Information (revised 6/2025).
- DailyMed. Guanfacine tablets USP (immediate-release), Prescribing Information.
- Iwanami A et al. (2020). Efficacy and safety of guanfacine extended-release in adults with ADHD: a phase 3 randomized, double-blind, placebo-controlled study. J Clin Psychiatry.
- Naya N et al. (2021). Guanfacine extended-release in Japanese adults with ADHD: post hoc subgroup analyses. Neuropsychopharmacol Rep, 41(1):26-39.