Guanfacine Dosages: Your GoodRx Guide

Guanfacine is an oral tablet that’s FDA approved to treat high blood pressure (hypertension) in adults. There’s also an extended-release (ER) tablet that’s approved for ADHD (attention-deficit hyperactivity disorder) in children. They’re both available as lower-cost generics. But only the ER form has a brand-name option (Intuniv).

Whenever your healthcare provider prescribes a new medication for you, it’s important to know exactly how to take it. Here, we’ll review common guanfacine dosages. But if your provider prescribes something different than what’s discussed below, talk with them to make sure you understand your individual dose.

What’s the typical guanfacine dosage for adults?

The typical guanfacine dosage depends on why you’re taking it, what product you’re using, and other factors, such as potential drug interactions.

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Hypertension

Guanfacine IR is approved to treat hypertension in adults. But it’s not a first-choice medication because it can have many side effects, including drowsiness and dizziness. That’s why it’s recommended that you take it at bedtime.

The recommended starting dose is 1 mg once daily at bedtime. In many cases, 1 mg will be enough to lower your blood pressure. But if it’s still high 3 to 4 weeks later, your healthcare provider might increase your dose to 2 mg at bedtime.

What’s the typical guanfacine dosage for children?

Guanfacine ER is approved to treat ADHD in children ages 6 to 17. It’s also been used off-label for treating children with ADHD who also have a tic disorder, and for adults with ADHD. But here, we’ll focus on its use for childhood ADHD.

The starting dosage is 1 mg daily. Your child’s healthcare provider may increase it weekly until an effective dose is reached. The final dosage is usually based on your child’s weight and ranges between 2 mg to 7 mg once daily. Regardless of your child’s weight, the maximum dose is 4 mg for children ages 6 to 12. The maximum dose for teens between 13 to 17 years old is 7 mg.

In most cases, it doesn’t matter when your child takes guanfacine ER, as long as it's taken at the same time each day. The ER tablets should be swallowed whole with a glass of water. Guanfacine ER shouldn’t be taken with a high-fat meal. This could cause guanfacine levels to increase in the body. Even foods that are high in unsaturated (“good”) fat — like nuts and fish — should be avoided. So should foods that are high in saturated fat, such as red meat, butter, and ice cream.

Good to know: Guanfacine ER isn’t usually a first-choice medication for childhood ADHD. A group of medications called stimulants are considered more effective. But if stimulants can’t be used due to side effects, guanfacine ER may be a good option. Or if your child is taking a stimulant, but it isn’t working well enough, guanfacine ER may be prescribed in addition to the stimulant medication. 

Guanfacine IR may sometimes be used off-label for ADHD. But research shows that when comparing guanfacine IR to ER, the IR formulation requires more dose adjustments and people are more likely to stop taking guanfacine IR than ER.

Are there any dosage adjustments for medical conditions?

There are a few factors your healthcare provider will consider when choosing your guanfacine dosage.

People with liver or kidney problems

There aren’t any specific dosage adjustments for people with liver or kidney problems. But if you have existing kidney or liver disease, you may need a lower dose of guanfacine. 

The same goes if you’re 65 or older. This is partly because you’re more likely to have kidney and liver problems as you age.

Possible drug interactions 

Guanfacine has some drug interactions to consider. Examples include:

• Medications that cause drowsiness. Drowsiness is a common side effect of guanfacine. So if you take it with other medications that make you tired, excessive drowsiness may occur. This includes medications such as diphenhydramine (Benadryl), certain antidepressants, and opioids.

• Medications that affect guanfacine ER levels. Guanfacine ER is metabolized (broken down) by certain enzymes (proteins) in the liver. If you take other medications or supplements that affect this enzyme, your blood levels of guanfacine ER might change. For example, medications such as diltiazem (Cardizem), ciprofloxacin (Cipro), and ketoconazole may increase guanfacine ER levels (so you may need a lower dose). Though, phenytoin (Dilantin, Phenytek), rifampin (Rifadin), and St. John’s wort may decrease guanfacine ER levels (so you may need a higher dose).

Be sure to share a list of all the medications and supplements you take with your provider and pharmacist. And keep them in the loop if you stop or start any medications. This will keep you safe while taking guanfacine.

What happens if you forget a dose of guanfacine?

If you forget to take a dose of guanfacine, take it as soon as you remember. But if you remember much later, and it’s close to your next scheduled dose, skip the missed dose altogether. Never take two doses at one time.

Stopping guanfacine suddenly can cause your blood pressure to spike (rebound hypertension). It can also cause side effects to occur when you restart the medication. So if you’re taking guanfacine ER and you miss two or more doses in a row, you might need to restart it at a lower dose. Your provider can give you instructions on how to do this. If you miss more than one dose of guanfacine IR in a row, talk to your provider about whether your dose needs adjustments.

What should you do if you take too much

Taking too much guanfacine increases your risk of side effects. Some possible risks of taking too much guanfacine include:

• Initially high blood pressure, then progression to low blood pressure

• Excessive drowsiness

• Slowed heart rate

• Dilated pupils

• Trouble breathing

Keep in mind that if you took too many ER tablets, the effects might not show up right away. 

If you or a loved one may have taken too much guanfacine and you’re experiencing any of the symptoms above, seek emergency care and call Poison Control at 1-800-222-1222.

How to save on guanfacine

There are many ways to save on guanfacine IR and ER. Both are available as lower-cost generics. GoodRx could help you save:

• Over 50% off the average retail price of guanfacine IR. Guanfacine IR at certain pharmacies may be as low as $12.87 with a free GoodRx discount.

• Over 90% off the average retail price of guanfacine ER. Guanfacine ER at certain pharmacies may be as low as $17.83 with a free GoodRx discount.

Why trust our experts?

Written by:

Daphne Berryhill, RPh

Daphne Berryhill, RPh, has two decades of experience as a clinical pharmacist. She spent most of her career in the Chicago area practicing in-home infusion.

Edited by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

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