thoughtscape NP Psychiatry · Patient education
Guanfacine
Intuniv (ER) / Tenex (IR)
A nonstimulant that can help attention and impulse control. The regular tablet also treats high blood pressure.
Draft for review · Clinical content has not been revalidated for this website.
IR and ER differ • Diagram labels reflect laboratory tests, not proven individual benefits.
What it is used for
ER tablets treat ADHD in children and teens, alone, or with a stimulant. Adult ADHD use is off-label in the US. IR tablets treat high blood pressure.
It may also be prescribed off-label for tics or related symptoms. Ask what your treatment should improve; feeling sleepy is not the goal.
How it works
It affects brain signaling involved in attention and impulse control. It is not a stimulant and does not work like a quick boost of energy.
It also reduces part of the body's alerting response. Blood pressure and pulse may fall, and you may feel sleepy or dizzy.
What to expect over time
THE FIRST FEW DAYS
Drowsiness, dry mouth, or dizziness may appear. Rise slowly and avoid driving until you know the effects.
AS THE DOSE CHANGES
Your team checks BP, pulse, and side effects. ER increases are no more frequent than weekly.
THE NEXT FEW WEEKS
Review focus, behavior, or your agreed goal. Benefit builds during dose adjustment; report excessive tiredness.
Taking your medication
Take it at the same time daily. ER may be taken morning or evening; follow your plan. Do not swap IR and ER or take both yourself.
Swallow ER tablets whole with water; never split, crush, or chew. Do not take ER with a high-fat meal. Ask about grapefruit.
Refill early. If vomiting or running out could interrupt treatment, call your team. Never double a dose or stop suddenly.
When to get help
Call 911: collapse, trouble breathing, seizure, severe allergy, chest pain, or stroke symptoms. For suspected overdose, call Poison Control: 1-800-222-1222 immediately.
Get urgent advice: fainting, severe dizziness, or a very slow pulse. New unusually high energy, little need for sleep or risky behavior also needs prompt review.
After missed/stopped doses: severe headache, racing heart, or chest tightness may mean rebound high blood pressure. Seek urgent care; do not self-adjust.
Early side effects
Sleepiness, fatigue, dizziness, dry mouth, constipation, headache, or stomach upset can occur. Fluids and fiber may help when appropriate. Avoid dehydration and overheating.
Other effects to discuss
Report persistent low energy, appetite, or sexual changes, sleep trouble, irritability, or urinary accidents. Do not assume ongoing problems must be tolerated.
What to keep track of
Keep BP/pulse checks. Track mood, sleep, daily function, and children's growth.
Before you start
Tell your team about fainting, low BP, a slow pulse, heart rhythm problems, stroke, kidney/liver disease, bipolar symptoms, or medication allergies. Review all medicines and supplements. An ECG or blood tests may be needed for your situation, but are not routine for everyone.
Medicines & interactions
Medicines that change the dose needed
Some antibiotics, antifungals, HIV medicines, nefazodone, carbamazepine, phenytoin, rifampin, and St. John's wort change guanfacine levels. Check before starting or stopping them.
Alcohol and sedatives
Avoid alcohol. Opioids, benzodiazepines, sleep medicines, and sedating allergy pills can increase impairment. Ask your pharmacist before combining them.
Blood-pressure and heart medicines
These may add dizziness, low BP, or a slow pulse. A stimulant does not cancel these risks or reliably prevent sleepiness.
Food and other guanfacine products
Avoid high-fat meals with ER and discuss grapefruit. Check the formulation on refills; IR and ER are not dose-for-dose substitutes.
Everyday tips
Use a daily reminder and a refill buffer.
Keep regular sleep, meals, and fluids.
Use ADHD or tic supports alongside medicine.
Bring a medicine list to every appointment.
Your questions, answered
What if I miss a dose?
For ER, skip it and take the next scheduled dose. Never double. If you miss two or more in a row, contact your prescriber before restarting; you may need a lower restart dose. IR instructions differ: check your pharmacy label.
Can I stop when I feel better?
Arrange a gradual reduction. Stopping suddenly can dangerously raise blood pressure, even though guanfacine is not controlled. If it makes you feel too slowed or unlike yourself, ask for an adjustment.
Is it safe with bipolar disorder?
Tell your team about past mood episodes. Unusually elevated or irritable mood and less need for sleep require review. Being a nonstimulant does not mean there is no mood risk.
Pregnant or breastfeeding?
Discuss an individual plan. Pregnancy and milk-transfer information is limited. Do not stop abruptly. If nursing, report unusual infant sleepiness, low energy, or poor feeding.
Storage & safety
Keep in the original container, away from heat and moisture, locked out of reach of children and pets. An overdose can have delayed effects; get advice immediately rather than waiting for symptoms. Never share medicine.
About this information
For general information only; not a substitute for individualized medical advice. This sheet does not cover every risk or interaction. Ask your prescriber or pharmacist before changing how you take this medication.
Sources
Educational inclusion does not mean this medication or its indications are treated at this practice. Review the guide for your exact product with your prescriber or pharmacist.