Guanfacine (Intuniv)
What is guanfacine?
Guanfacine is known as Intuniv in the United States and Japan alike (インチュニブ on Japanese packaging). It's a non-stimulant medicine for ADHD. It acts on alpha-2A adrenergic receptors and is thought to adjust signalling in the prefrontal cortex, the part of the brain involved in attention and impulse control; the exact way it helps ADHD isn't fully understood.
How is it different from stimulant ADHD medicines?
- Not a controlled medicine in Japan: no registration system, normal import rules when travelling, and any doctor can prescribe it
- A different route: it works on a different signalling system from stimulants, so it's an option when a stimulant isn't suitable, isn't enough, or isn't wanted
- No known abuse or dependence potential: its main side effect is sleepiness rather than wakefulness
- Approved for both children and adults in Japan: the dose is set by age and body weight
What is it used for in Japan?
ADHD (attention-deficit / hyperactivity disorder), in children from age 6 and in adults.
How does it help?
It is thought to steady attention and settle impulsivity and restlessness by adjusting noradrenaline signalling in the prefrontal cortex. Like atomoxetine, it builds up gradually: the benefit builds over the first weeks, as the dose is raised step by step, so keep taking it as prescribed even if you don't notice a change at first.
Guanfacine, atomoxetine, or Concerta: which is right for me?
There's no universal winner; the three trade different strengths, and the choice is individual.
| Concerta (stimulant) | Atomoxetine (non-stimulant) | Guanfacine (non-stimulant) | |
|---|---|---|---|
| Speed | Works from day one | Builds over a few weeks | Builds over one to a few weeks |
| Effect | Often somewhat stronger on average, most clearly in children | Solid and steady, focus-led | Solid, especially on impulsivity and restlessness |
| Coverage | About 12 hours; can fade in the evening | Around the clock | Around the clock |
| Rules | Controlled medicine: registered doctors, pharmacies, and patients only | Ordinary medicine: any doctor, normal import rules | Ordinary medicine: any doctor, normal import rules |
| Habit-forming potential | Can be misused, so it is tightly controlled | None | None |
| Getting it right now | Shipments restricted since September 2025 and still restricted in October 2026; ask your clinic | Strattera brand no longer made; atomoxetine from other makers is available | Normally available |
Plenty of people do well on any of the three, switching is routine, and it's a decision you make with your doctor.
What should I tell my doctor before starting?
A few situations rule it out entirely; your doctor will choose something else if any of these apply:
- A past allergic reaction to guanfacine
- Pregnancy, or the possibility of being pregnant (see the section below; guanfacine is one of the few psychiatric medicines that is formally ruled out in pregnancy)
- A significant heart block (second- or third-degree AV block, a specific heart-rhythm condition)
And tell your doctor first if any of these apply; these usually just need adjustments or a closer eye:
- Low blood pressure, blood pressure that drops when you stand up, a slow heartbeat, a heart rhythm problem (including long QT syndrome), angina, a past heart attack, or a past stroke
- High blood pressure now or in the past (the rebound on stopping is a particular concern)
- Depression (the sedation can make low mood worse)
- Serious liver or kidney problems (a lower starting dose is used)
- Other blood-pressure medicines, medicines that slow the heart or affect heart rhythm, or sedating medicines
- Certain antifungals and antibiotics (such as itraconazole or clarithromycin), which raise the level of guanfacine, or carbamazepine, which lowers it
- Valproate, since guanfacine can raise its level
- Planning a pregnancy, or breastfeeding (see the section below)
Your blood pressure and pulse are checked before starting, after each dose change, and regularly after that, since guanfacine lowers blood pressure and can slow the heart; an ECG is checked before starting, and your weight from time to time.
How do I take it, and what if I miss a dose?
Guanfacine is taken once a day, and the tablet is swallowed whole (don't crush or chew it; it's a slow-release design).
- If you miss a dose: take it when you remember, unless the next dose is close; in that case just skip. Never take a double dose to catch up. If you've missed two or more days in a row, check with your doctor before going back to your usual dose
- Sleepiness: strongest when starting and after each dose increase; if it gets in the way, tell your doctor, as the dose and timing can be adjusted
- Alcohol: be careful with it; the Japanese label warns that the two can strengthen each other's sedating effects
What side effects should I expect?
Most are mild and often settle, and many can be eased by adjusting the dose or timing. Not everyone gets them; the rough figures below just give a sense of how common each one is.
- Drowsiness or sleepiness (very common: around 50%): strongest when starting and after dose increases; tell your doctor if it gets in the way, and the dose or timing can be adjusted
- Low blood pressure (around 20%) or a slow pulse (around 15%): most noticeable when starting and when the dose changes, and more often in adults than in children; the blood pressure checks pick it up and the dose is adjusted. Stand up slowly, and drink enough fluids
- Headache
- Dizziness, especially on standing up
- Tiredness
- Dry mouth
- Constipation
If anything is bothering you, tell your doctor; there's often a way to adjust.
Finally, two things that are rare (most people never experience them) but good to know:
- Feeling faint, or actually fainting: sit or lie down if you feel it coming, and tell your doctor if it happens; the dose and your blood pressure will be reviewed
- A change in mood, new thoughts of self-harm, or a rise in aggression: the Japanese label asks doctors to watch for these; tell your doctor promptly if you or your family notice them
Will I become dependent? How do I stop safely?
No; guanfacine isn't habit-forming, but it should never be stopped abruptly. Stopping suddenly can cause a rebound rise in blood pressure and a fast heartbeat, so your doctor lowers it gradually, one step at a time with a few days between steps, checking your blood pressure and pulse along the way. Time any change together rather than deciding alone.
Can I drive while taking it?
The Japanese label advises against driving while taking it. Guanfacine's drowsiness is significant, especially early on, and the prescribing information here instructs that patients on it shouldn't drive or operate dangerous machinery. Discuss your own situation with your doctor.
What about pregnancy and breastfeeding?
Guanfacine is not used in pregnancy; this is a formal rule, not a judgement call. The Japanese label lists pregnancy, and the possibility of pregnancy, as a reason not to prescribe it. If you're taking it and planning a pregnancy, or discover you're pregnant, contact your doctor promptly rather than stopping on your own (sudden stops rebound on blood pressure); the switch is planned with your doctor. With breastfeeding, the label leaves the decision to be weighed individually, so it's decided case by case. Our guides to medication in pregnancy and medication while breastfeeding cover the details.