guanfacine
Brand names: Intuniv, Tenex
Guanfacine extended-release tablets can help treat ADHD. It can be used alone or with stimulant medicines.
Drug Shortage Alert
guanfacine is currently listed as to be discontinued by the FDA. Affected manufacturer: Actavis Pharma, Inc..
View all drug shortages →Drug Pricing (NADAC)
Generic Price
$0.17/unit
Generic Available
Yes (19 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Guanfacine extended-release tablets are used to treat Attention Deficit Hyperactivity Disorder (ADHD).
Common side effects
Feeling sleepy or tired, Low blood pressure, Dizziness
Key warnings
Guanfacine can cause low blood pressure, slow heart rate, and fainting.
How It Works
Guanfacine is a central alpha 2A-adrenergic receptor agonist. This means it works by stimulating specific receptors in the brain. By stimulating these receptors, guanfacine helps to improve attention and reduce impulsivity and hyperactivity in people with ADHD.
How to Take It
Take guanfacine extended-release tablets once a day. You can take it in the morning or evening, but take it at the same time each day. Swallow the tablets whole; do not crush, chew, or break them. Do not take it with high-fat meals.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant or plan to become pregnant. There is a pregnancy registry for women who take ADHD medicines during pregnancy. Talk to your doctor if you are breastfeeding or plan to breastfeed. Monitor breastfed infants for sleepiness, lethargy, and poor feeding.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store guanfacine extended-release tablets at room temperature (68° - 77°F).
Side Effects (from patient reports)
Based on 3,888 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 7,386 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
7,386
Death-Related Reports
228
Hospitalization Reports
1,757
Top Indication
Attention Deficit/Hyperactivity Disorder
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DRUG INEFFECTIVE | 778 |
| 2 | OFF LABEL USE | 598 |
| 3 | SOMNOLENCE | 455 |
| 4 | AGGRESSION | 376 |
| 5 | FATIGUE | 329 |
| 6 | HYPOTENSION | 289 |
| 7 | DIZZINESS | 270 |
| 8 | HEADACHE | 268 |
| 9 | INSOMNIA | 264 |
| 10 | SUICIDAL IDEATION | 259 |
| 11 | ANXIETY | 250 |
| 12 | BRADYCARDIA | 249 |
| 13 | NAUSEA | 245 |
| 14 | ABNORMAL BEHAVIOUR | 215 |
| 15 | TOXICITY TO VARIOUS AGENTS | 213 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Guanfacine can cause low blood pressure, slow heart rate, and fainting. Tell your doctor if you have heart problems. This medicine can also cause sleepiness, so be careful driving or using heavy machinery. Stopping guanfacine suddenly can cause high blood pressure. Your doctor will slowly lower your dose when you stop taking it.
Known Drug Interactions
Table 14: Clinically Important Drug Interactions: Effect of other Drugs on Guanfacine Concomitant Drug Name or Drug Class Clinical Rationale and Magnitude of Drug Interaction Clinical Recommendation Strong and moderate CYP3A4 inhibitors, e.g., ketoconazole, fluconazole Guanfacine is primarily metabolized by CYP3A4 and its plasma concentrations can be significantly affected resulting in an increase in exposure Consider dose reduction [see Dosage and administration (2.7)] Strong and moderate CYP3A4 inducers, e.g., rifampin, efavirenz Guanfacine is primarily metabolized by CYP3A4 and its plasm...
Mechanism: Ketoconazole stops the body from breaking down guanfacine, which can cause the drug to build up to high levels.
What to do: Your doctor may need to lower your guanfacine dose while you are taking these drugs together.
Table 14: Clinically Important Drug Interactions: Effect of other Drugs on Guanfacine Concomitant Drug Name or Drug Class Clinical Rationale and Magnitude of Drug Interaction Clinical Recommendation Strong and moderate CYP3A4 inhibitors, e.g., ketoconazole, fluconazole Guanfacine is primarily metabolized by CYP3A4 and its plasma concentrations can be significantly affected resulting in an increase in exposure Consider dose reduction [see Dosage and administration (2.7)] Strong and moderate CYP3A4 inducers, e.g., rifampin, efavirenz Guanfacine is primarily metabolized by CYP3A4 and its plasm...
Mechanism: Fluconazole slows down how fast your body processes guanfacine, leading to higher amounts of the drug in your system.
What to do: Your doctor may need to reduce your dose of guanfacine to prevent it from reaching unsafe levels.
Table 14: Clinically Important Drug Interactions: Effect of other Drugs on Guanfacine Concomitant Drug Name or Drug Class Clinical Rationale and Magnitude of Drug Interaction Clinical Recommendation Strong and moderate CYP3A4 inhibitors, e.g., ketoconazole, fluconazole Guanfacine is primarily metabolized by CYP3A4 and its plasma concentrations can be significantly affected resulting in an increase in exposure Consider dose reduction [see Dosage and administration (2.7)] Strong and moderate CYP3A4 inducers, e.g., rifampin, efavirenz Guanfacine is primarily metabolized by CYP3A4 and its plasm...
Mechanism: Rifampin causes your body to break down guanfacine much faster than normal, which can make the drug less effective.
What to do: Your doctor may need to increase your guanfacine dose to ensure the medicine still works for you.
Bosentan Guanfacine Monitor for adverse reactions.
Mechanism: Itraconazole blocks the process that clears guanfacine from your system. This leads to higher levels of the drug in your body.
What to do: Watch for side effects and have your healthcare provider check your response to the medication.
7.2 Drugs Having No Clinically Important Interactions with Lisdexamfetamine Dimesylate Capsules From a pharmacokinetic perspective, no dose adjustment of lisdexamfetamine dimesylate capsules is necessary when lisdexamfetamine dimesylate capsules is co-administered with guanfacine, venlafaxine, or omeprazole. In addition, no dose adjustment of guanfacine or venlafaxine is needed when lisdexamfetamine dimesylate capsules is co-administered [see Clinical Pharmacology (12.3) ] .
Mechanism: These two drugs do not change how the body processes each other. They can be used together without affecting the amount of medicine in your blood.
What to do: No dose changes are needed when taking these two medications together. You can continue your current treatment plan as directed by your doctor.
Common Questions
Can I crush the tablet?
Can I take this with food?
What should I do if I feel dizzy?
Can I drive while taking this medicine?
What happens if I stop taking it suddenly?
How often should my blood pressure be checked?
What if I am taking other medications?
Can this medication cause heart problems?
What is the starting dose?
How will my dose be adjusted?
What are the common side effects of guanfacine?
Does guanfacine interact with other medications?
What drug class is guanfacine?
Is guanfacine safe during pregnancy?
Is guanfacine currently in shortage?
Related Medications in Central Alpha-2 Agonist
Other drugs grouped near guanfacine — same-class peers and common alternatives.
acamprosate
Campral
Acamprosate is a medicine that can help you stay away from alcohol if you are alcohol-dependent and have already stopped drinking.
Compare with guanfacine →
alprazolam
Xanax
Alprazolam (Xanax) is a medication that can help you with anxiety and panic disorders.
Compare with guanfacine →
amitriptyline
Elavil
Amitriptyline is a medicine used to treat depression.
Compare with guanfacine →
amphetamine/dextroamphetamine
Adderall, Adderall XR
Adderall XR is a stimulant medicine.
Compare with guanfacine →
aripiprazole
Abilify
Aripiprazole (Abilify) is a medicine used to treat certain mental disorders and mood problems.
Compare with guanfacine →
Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
Related Health & Safety Data
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What the FDA Data Shows for guanfacine
The FDA label for guanfacine (sold under brand names such as Intuniv, Tenex) classifies it as a prescription-only medication in the Central Alpha-2 Agonist class. Guanfacine extended-release tablets are used to treat Attention Deficit Hyperactivity Disorder (ADHD). Official labeling lists 6 commonly reported side effects, including Feeling sleepy or tired, Low blood pressure, Dizziness.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 3,888 voluntary reports. The database also lists 5 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. NADAC pricing from CMS shows a generic unit cost of $0.17.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC). Shortage status: FDA Drug Shortages Database.
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: January 23, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages