Guanfacine
~18 h adolescents/adults
XR: 1, 2, 3, 4 mg
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Attention-deficit/hyperactivity disorder (ADHD) — extended-release (Intuniv) | Children and adolescents 6–17 years | Monotherapy or adjunctive to stimulants | FDA Approved |
| Hypertension — immediate-release (Tenex) | Adults | Monotherapy or with a thiazide diuretic | FDA Approved |
| ADHD in adults | Adults ≥18 years | Monotherapy or adjunctive (typically with stimulant) | Off-Label |
| Tourette syndrome & chronic tic disorders | Children and adolescents | Monotherapy | Off-Label |
The extended-release formulation (Intuniv) was FDA-approved in 2009 for pediatric ADHD and is one of two non-stimulant medications, alongside atomoxetine, with a specific FDA indication in this population (clonidine extended-release is also approved). Its non-stimulant profile, lack of abuse potential, and complementary mechanism to stimulants make it useful in patients with comorbid tic disorders, anxiety, or sleep disturbance, and in families concerned about controlled-substance prescribing. The immediate-release formulation (Tenex) retains an antihypertensive indication but is not recommended as first-line therapy for hypertension in current guidelines.
Tourette syndrome & chronic tic disorders — supported by the AAN 2019 practice guideline as a treatment option for tics; randomized data show modest reduction. Evidence quality: moderate.
Anxiety, hyperarousal and irritability in autism spectrum disorder — small randomized and open-label studies suggest symptomatic benefit. Evidence quality: low.
PTSD-related nightmares and hyperarousal — small studies and case series; benefit less consistent than for prazosin. Evidence quality: low.
Adult ADHD adjunctive therapy — commonly prescribed as add-on to stimulants for residual symptoms; meta-analyses suggest moderate effect. Evidence quality: moderate.
Opioid withdrawal symptom control — clonidine has the larger evidence base in this setting; comparative data for guanfacine are limited. Evidence quality: very low.
Dosing
The two formulations are not interchangeable on a milligram-for-milligram basis. The extended-release tablet (Intuniv) is dosed once daily for ADHD, in the morning or evening, and titrated weekly. The immediate-release tablet (Tenex) is typically dosed at bedtime for hypertension to minimize daytime sedation. The recommended target weight-based range for Intuniv is 0.05–0.12 mg/kg/day.
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| ADHD — children 6–12 yr (XR / Intuniv) — monotherapy | 1 mg PO once daily | 1–4 mg/day | 4 mg/day | Titrate by no more than 1 mg/week; weight-based target 0.05–0.12 mg/kg/day Doses above 4 mg/day have not been evaluated in this age group |
| ADHD — adolescents 13–17 yr (XR / Intuniv) — monotherapy | 1 mg PO once daily | 1–7 mg/day | 7 mg/day | Titrate by no more than 1 mg/week; many adolescents respond at 4–7 mg/day Doses above 7 mg/day have not been evaluated |
| ADHD — adjunctive to a stimulant (XR / Intuniv) | 1 mg PO once daily | 1–4 mg/day | 4 mg/day | Same titration cadence as monotherapy; monitor for additive bradycardia/hypotension Doses above 4 mg/day have not been studied in adjunctive trials |
| Hypertension — adults (IR / Tenex) | 1 mg PO at bedtime | 1–3 mg HS | 3 mg/day | If inadequate after 3–4 weeks, increase to 2 mg, then 3 mg Doses >3 mg/day add little benefit and worsen adverse effects |
| Tourette syndrome / chronic tic disorder (off-label, pediatric) | 0.5–1 mg/day | 1–4 mg/day divided | ~4 mg/day | IR formulation often used in 2–3 divided doses; titrate slowly over 4–6 weeks Tic response is gradual; reassess at 8–12 weeks |
| Switching between IR and XR | Discontinue current formulation and titrate the new one starting at 1 mg/day | Do not substitute mg-for-mg — XR has lower Cmax and AUC than the same IR dose Follow standard XR titration schedule when switching | ||
Dose Adjustments in Special Populations
| Population | Recommendation | Rationale |
|---|---|---|
| Hepatic impairment (clinically significant) | Consider dose reduction | Approximately 50% of clearance is hepatic via CYP3A4/5 |
| Renal impairment (clinically significant) | Consider dose reduction | Approximately 50% of guanfacine is excreted unchanged in urine |
| Strong or moderate CYP3A4 inhibitor co-administration | Reduce Intuniv dose to 50% of target | Inhibitors substantially raise guanfacine plasma exposure |
| Strong or moderate CYP3A4 inducer co-administration | Consider titrating up to 2× the target dose over 1–2 weeks | Inducers can substantially lower guanfacine exposure and reduce efficacy |
| Elderly (HTN indication) | Start 1 mg HS; titrate cautiously | Higher risk of orthostasis, falls, and bradycardia |
Discontinuation
Guanfacine should not be stopped abruptly. The Intuniv label specifies that the total daily dose should be tapered in decrements of no more than 1 mg every 3–7 days to minimize the risk of rebound hypertension. The risk is greater at higher doses, with concomitant stimulant use, and after prolonged therapy.
Intuniv tablets must be swallowed whole — never crushed, chewed, or split — because disrupting the matrix accelerates release and produces immediate-release pharmacokinetics with risk of hypotension and sedation. Co-administration with a high-fat meal increases Cmax by approximately 75% and AUC by approximately 40%, so high-fat meals should be avoided. After two or more consecutive missed doses, consider re-titrating based on tolerability.
Pharmacology
Mechanism of Action
Guanfacine is a selective post-synaptic α2A-adrenergic receptor agonist with substantially greater affinity (reported as 15–20 fold) for the α2A subtype than for α2B or α2C subtypes — the feature that distinguishes it pharmacologically from clonidine and explains its more favourable sedation and cardiovascular profile. In the prefrontal cortex, α2A activation on pyramidal neurons is hypothesized to strengthen functional network connectivity and improve working memory and behavioural inhibition; this central action is believed to underlie its therapeutic effect in ADHD. Peripherally, agonism at brainstem α2 receptors reduces sympathetic outflow, producing a fall in peripheral vascular resistance, heart rate, and blood pressure that accounts for both its antihypertensive effect and its principal cardiovascular adverse effects. Unlike stimulants, guanfacine is not a CNS stimulant, has no abuse potential, and does not increase synaptic dopamine or noradrenaline in the striatum.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Readily absorbed; Tmax ~5 h (XR, paediatric); 4–8 h (XR, adults); 1–4 h (IR). High-fat meal raises Cmax ~75% and AUC ~40% (XR) | Take XR consistently; avoid high-fat meals to prevent peak-related toxicity |
| Distribution | Vd 6.3 L/kg (after IV dosing); apparent oral Vd higher in paediatric patients (~24 L/kg in children, ~20 L/kg in adolescents); protein binding 64–72% (chiefly albumin) | Wide tissue distribution; protein binding low enough that displacement interactions are clinically minor |
| Metabolism | Hepatic via CYP3A4 (and CYP3A5); main metabolite 3-hydroxy-guanfacine (and its glucuronide and sulfate conjugates) | Susceptible to CYP3A4 inhibitors and inducers; dose adjustment required (see Interactions) |
| Elimination | ~50% excreted unchanged in urine; remainder as metabolites; t½ ~14 h in children, ~18 h in adolescents and adults (range reported 10–30 h) | Once-daily XR dosing supported by long half-life; clearance reduced in significant renal or hepatic impairment |
Side Effects
The adverse-effect profile is dominated by sedation, fatigue, and cardiovascular effects (hypotension, bradycardia). Most adverse effects are dose-related, attenuate over the first weeks of therapy, and respond to slower titration. Frequencies below are taken from the Intuniv FDA prescribing information (fixed-dose paediatric monotherapy Studies 1 and 2; n=513 on Intuniv vs n=149 placebo) and the Tenex FDA prescribing information for adult hypertension. In the Intuniv tables the term “somnolence” encompasses somnolence, sedation, and hypersomnia, and the term “hypotension” encompasses hypotension and orthostatic and diastolic/systolic blood-pressure decreases.
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Somnolence (umbrella: somnolence/sedation/hypersomnia) — Intuniv paediatric | 38% | Versus 11% placebo in fixed-dose trials; rises with dose (28% at 1 mg, 51% at 4 mg). Peaks early in therapy and usually attenuates |
| Headache — Intuniv paediatric | 23% | Versus 19% placebo; usually mild and transient |
| Fatigue — Intuniv paediatric | 14% | Versus 3% placebo; distinct from sedation; can persist beyond initial weeks |
| Abdominal pain (umbrella term) — Intuniv paediatric | 11% | Versus 9% placebo; rises with dose. Take with light food if tolerated |
| Dry mouth — Tenex IR adult HTN | up to 47% | Dose-dependent; far more frequent with IR formulation in adults than with XR in paediatric trials |
| Constipation — Tenex IR adult HTN | up to 16% | Dose-related; address with hydration, fibre, and osmotic laxatives if needed |
| Somnolence — Tenex IR adult HTN | up to 10–21% | Bedtime dosing minimizes daytime impact |
| Fatigue — Tenex IR adult HTN | ~12% | Similar pattern to paediatric population; usually improves with continued therapy |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Hypotension (umbrella term) — Intuniv paediatric | 7% | Versus 3% placebo; orthostatic hypotension reported in ~1%. Check seated and standing BP at each dose increase |
| Lethargy — Intuniv paediatric | 6% | Versus 3% placebo; overlaps with somnolence; consider dose reduction if functioning declines |
| Dizziness — Intuniv paediatric | 6% | Often orthostatic; counsel on slow positional changes |
| Nausea — Intuniv paediatric | 6% | Generally improves with continued therapy |
| Decreased appetite — Intuniv paediatric | 6% | Less appetite suppression than stimulants; track weight in children |
| Irritability — Intuniv paediatric | 6% | Distinguish from underlying ADHD/mood symptoms; reassess if worsening |
| Dry mouth — Intuniv paediatric | 4% | Less prominent than with the IR formulation in adults |
| Constipation — Intuniv paediatric | 3% | Hydration and fibre usually sufficient |
| Insomnia (umbrella term) — Intuniv paediatric | ~2–13% | Range across trials; paradoxical despite sedation; review dose timing |
| Bradycardia — Intuniv paediatric | 2–5% | Document baseline HR; symptomatic bradycardia warrants dose review |
| Nightmare/abnormal dreams — Intuniv paediatric | 2% | Rises with dose; usually self-limiting |
| Enuresis (umbrella term) — Intuniv paediatric | 2% | Includes nocturia and urinary incontinence; rare in adults |
| First-degree AV block — Intuniv paediatric | <2% | Listed as <2% adverse reaction in fixed-dose trials |
| Asthenia — Tenex IR adult HTN | ~6% | Generalized weakness; distinguish from sedation |
| Impotence — Tenex IR adult HTN | listed as ≤3% | Reported as a reason for dropout in adult trials; usually reversible on discontinuation |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Syncope | ~1% (paediatric, mostly long-term open-label) | During titration or with dehydration/heat | Withhold dose; assess vitals; reduce dose or alternative; counsel on hydration |
| Symptomatic hypotension / orthostasis | Uncommon | Days to weeks; greater on dose increases | Reduce or hold dose; review concomitant antihypertensives |
| Symptomatic bradycardia | Rare | Variable; risk increases with sympatholytic co-medication | ECG; cardiology referral; discontinue if persistent symptoms |
| Atrioventricular block (worsening of pre-existing or new) | Rare | Any time; greater risk with concomitant sympatholytic drugs | ECG; cardiology evaluation; usually requires discontinuation |
| Rebound hypertension on abrupt discontinuation (with reports of hypertensive encephalopathy) | Class effect; rare with proper taper (postmarketing) | Within days of stopping; greater risk at higher doses and with stimulant co-use | Reinitiate guanfacine and taper slowly; daily BP monitoring; emergency care if encephalopathic features |
| Hypersensitivity reactions (rash, exfoliative dermatitis, pruritus) | Rare | Any time | Discontinue; supportive care; future use contraindicated |
| Hallucinations | Postmarketing reports; very rare | Variable | Discontinue; psychiatric evaluation |
| Reason for Discontinuation | Incidence (Paediatric XR, Fixed-Dose Monotherapy) | Context |
|---|---|---|
| Somnolence / sedation / hypersomnia | 6% (vs 1% placebo) | Most common cause overall; rises with dose (3% at 1 mg, 11% at 4 mg) |
| Fatigue | 2% (vs 0% placebo) | Persistent fatigue beyond 4 weeks should prompt dose review |
| Hypotension | ~1% | Met the ≥2% threshold in some dose groups but not across all doses combined |
| Headache | ~1% | Less commonly the lone reason for stopping |
| Dizziness | ~1% | Usually orthostatic in nature |
Sedation peaks early in titration and is the leading cause of discontinuation. Strategies that improve tolerability without giving up therapeutic benefit: (1) advance dose by 1 mg only every 1–2 weeks rather than weekly in sensitive patients; (2) shift the dose to bedtime if morning sedation predominates; (3) reassess concurrent CNS depressants such as antihistamines, anticonvulsants, or sleep aids. Most cases improve substantially over weeks of continued therapy.
Drug Interactions
Guanfacine is a CYP3A4 substrate, so the most clinically meaningful interactions involve strong and moderate CYP3A4 inhibitors and inducers. Pharmacodynamic interactions — additive sedation with CNS depressants and additive hypotension and bradycardia with cardiovascular drugs — are also frequent in real-world practice. Guanfacine does not significantly affect the pharmacokinetics of methylphenidate or lisdexamfetamine.
Monitoring
The Intuniv prescribing information specifies measuring heart rate and blood pressure prior to initiation, following dose increases, and periodically while on therapy. Paediatric patients on chronic therapy additionally need growth and behavioural surveillance.
-
Blood pressure
Baseline; after each dose change; periodically thereafter
Routine Document seated and standing values during titration. Symptomatic orthostasis or significant decline below age-appropriate norms warrants pause and reassessment. -
Heart rate
Baseline; after each dose change; periodically thereafter
Routine A resting HR below age-appropriate norms or symptomatic bradycardia should prompt dose review. -
Cardiac history & ECG
Baseline cardiac history at initiation; ECG if risk factors
Trigger-based Indicated when there is a personal or family history of structural heart disease, sudden cardiac death, arrhythmia, or use of other sympatholytic or AV-nodal-blocking agents. -
Sedation & alertness
Each visit during titration and first weeks
Routine Use parent or teacher report or self-rating in adolescents. Persistent functional sedation beyond several weeks warrants dose reduction. -
ADHD response
Baseline; reassess at 4–6 weeks; then every 3–6 mo
Routine Validated rating scales (Vanderbilt, SNAP-IV, ADHD-RS) at home and school improve sensitivity to change. -
Growth (paediatric)
Periodically (e.g., every 6 mo)
Routine Plot weight and height percentiles. Long-term Intuniv data show normal growth trajectories, but ongoing surveillance is reasonable. -
Mood & behaviour
Each visit, especially during titration
Routine Ask about mood change, irritability, and unusual experiences. Hallucinations have been reported postmarketing. -
Renal function
If CKD risk; if signs of accumulation
Trigger-based About half of guanfacine is excreted unchanged in urine. Routine monitoring in healthy patients is not required. -
Hepatic function
If clinical suspicion or hepatotoxic co-medication
Trigger-based No routine LFT screening required for guanfacine alone. -
Adherence & taper plan
Each visit; explicitly before any planned discontinuation
Routine Confirm taper plan in writing. Children with vomiting illnesses are at particular risk for unintentional rebound hypertension.
Contraindications & Cautions
Absolute Contraindications
- History of hypersensitivity to guanfacine, its inactive ingredients, or other products containing guanfacine. Rash and pruritus have been reported and exfoliative dermatitis has been described with the immediate-release product.
Relative Contraindications — Specialist Input Recommended
- Pre-existing heart block, sinus node dysfunction, or significant baseline bradycardia — cardiology input before initiation, given potential to worsen these.
- History of syncope or conditions predisposing to syncope (orthostatic hypotension, dehydration).
- Recent myocardial infarction or unstable cardiovascular disease.
- Cerebrovascular disease — risk of cerebral hypoperfusion with abrupt BP lowering.
- Severe hepatic impairment — reduced clearance; consider dose reduction with specialist input.
- Severe renal impairment — consider dose reduction with specialist input.
- Concurrent strong or moderate CYP3A4 inhibitors that cannot be substituted — reduce Intuniv to 50% of target dose and monitor closely.
Use with Caution
- Elderly patients — higher orthostatic hypotension and fall risk.
- Patients on multiple antihypertensives or other sympatholytic drugs — additive effects on BP, HR, and AV conduction likely.
- Pregnancy — no adequate, well-controlled human studies; use only if benefit justifies fetal risk.
- Lactation — observe nursing infants for sedation and somnolence.
- Operating heavy machinery or driving — particularly during titration.
- Children with intercurrent vomiting illness — missed doses can lead to rebound hypertension.
- Concurrent alcohol or other CNS depressants — advise patients to avoid.
The Intuniv prescribing information warns that abrupt discontinuation can lead to clinically significant and persistent rebound hypertension above baseline levels and increases in heart rate. Hypertensive encephalopathy has been reported in association with rebound hypertension with both Intuniv and immediate-release guanfacine, particularly with high-dose therapy and concomitant stimulant use. Children commonly have gastrointestinal illnesses that lead to vomiting and inability to take medications, placing them at particular risk.
To minimize this risk, the total daily dose should be tapered in decrements of no more than 1 mg every 3–7 days. Blood pressure and heart rate should be monitored when reducing the dose or discontinuing therapy. This is a class effect shared with other centrally acting α2-agonists such as clonidine.
Patient Counselling
Purpose of Therapy
For ADHD, guanfacine works differently from stimulants. It activates a specific receptor in the front of the brain that supports focus, attention, and impulse control, often with additional benefit for irritability or sleep. It is not a stimulant, has no abuse potential, and benefit usually emerges over 2–4 weeks once the effective dose is reached, rather than within hours like stimulants. For hypertension, guanfacine reduces blood pressure by lowering the signal from the brain that tells blood vessels to constrict.
How to Take
The extended-release tablet is taken once daily at the same time each day, in the morning or evening. It must be swallowed whole and never crushed, chewed, or split. Avoid taking it with a high-fat meal because this can cause too much medicine to be released at once. The immediate-release tablet for blood pressure is usually taken at bedtime to reduce daytime drowsiness. If two or more doses are missed in a row, the prescriber may need to re-titrate the dose. Never double up on a missed dose.
Sources
- Intuniv (guanfacine) extended-release tablets — full prescribing information. U.S. Food and Drug Administration. Available at accessdata.fda.gov Primary source for ADHD dosing tables, pediatric trial adverse-event tables, CYP3A4 dose-adjustment guidance, and the rebound hypertension warning.
- Tenex (guanfacine hydrochloride) immediate-release tablets — full prescribing information. U.S. Food and Drug Administration. Available at accessdata.fda.gov Primary source for adult hypertension dosing, the IR-formulation adverse-event profile (dry mouth, constipation, asthenia, impotence), and discontinuation/rebound warnings.
- Intuniv Summary of Product Characteristics. European Medicines Agency. Available at ema.europa.eu European regulatory perspective; aligns with the FDA label on dosing and adverse events.
- Biederman J, Melmed RD, Patel A, et al. A randomized, double-blind, placebo-controlled study of guanfacine extended release in children and adolescents with attention-deficit/hyperactivity disorder. Pediatrics. 2008;121(1):e73–e84. doi:10.1542/peds.2006-3695 Pivotal pediatric monotherapy trial that established Intuniv efficacy and dose-response in ADHD.
- Sallee FR, McGough J, Wigal T, et al. Guanfacine extended release in children and adolescents with attention-deficit/hyperactivity disorder: a placebo-controlled trial. J Am Acad Child Adolesc Psychiatry. 2009;48(2):155–165. doi:10.1097/CHI.0b013e318191769e Second pivotal trial confirming efficacy in 6–17-year-olds with detailed adverse-event characterization.
- Wilens TE, Bukstein O, Brams M, et al. A controlled trial of extended-release guanfacine and psychostimulants for attention-deficit/hyperactivity disorder. J Am Acad Child Adolesc Psychiatry. 2012;51(1):74–85.e2. doi:10.1016/j.jaac.2011.10.012 Adjunctive-to-stimulant trial supporting combination-therapy approval.
- Newcorn JH, Stein MA, Childress AC, et al. Randomized, double-blind trial of guanfacine extended release in children with attention-deficit/hyperactivity disorder: morning or evening administration. J Am Acad Child Adolesc Psychiatry. 2013;52(9):921–930. doi:10.1016/j.jaac.2013.06.006 Comparative timing study informing flexible morning vs evening administration schedules.
- Wolraich ML, Hagan JF, Allan C, et al. Clinical practice guideline for the diagnosis, evaluation, and treatment of attention-deficit/hyperactivity disorder in children and adolescents. American Academy of Pediatrics. Pediatrics. 2019;144(4):e20192528. doi:10.1542/peds.2019-2528 Current AAP guideline addressing the place of guanfacine among non-stimulant options.
- Pliszka S, AACAP Work Group on Quality Issues. Practice parameter for the assessment and treatment of children and adolescents with attention-deficit/hyperactivity disorder. J Am Acad Child Adolesc Psychiatry. 2007;46(7):894–921. doi:10.1097/chi.0b013e318054e724 AACAP framework for sequencing stimulants and α2-agonists in pediatric ADHD.
- Pringsheim T, Okun MS, Mller-Vahl K, et al. Practice guideline recommendations summary: treatment of tics in people with Tourette syndrome and chronic tic disorders. American Academy of Neurology. Neurology. 2019;92(19):896–906. doi:10.1212/WNL.0000000000007466 AAN guideline supporting α2-agonists, including guanfacine, as treatment options for tics.
- National Institute for Health and Care Excellence. Attention deficit hyperactivity disorder: diagnosis and management (NG87). London: NICE; updated 2019. Available at nice.org.uk UK guideline; positions guanfacine as a non-stimulant option after stimulants and atomoxetine.
- Arnsten AFT. The use of α2A-adrenergic agonists for the treatment of attention-deficit/hyperactivity disorder. Expert Rev Neurother. 2010;10(10):1595–1605. doi:10.1586/ern.10.133 Authoritative mechanistic review on α2A agonism in prefrontal cortex and ADHD.
- Sorkin EM, Heel RC. Guanfacine: a review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in the treatment of hypertension. Drugs. 1986;31(4):301–336. doi:10.2165/00003495-198631040-00003 Foundational pharmacology review covering the immediate-release formulation in hypertension.
- Boellner SW, Pennick M, Fiske K, Lyne A, Shojaei A. Pharmacokinetics of a guanfacine extended-release formulation in children and adolescents with attention-deficit/hyperactivity disorder. Pharmacotherapy. 2007;27(9):1253–1262. doi:10.1592/phco.27.9.1253 Pediatric PK study supporting once-daily dosing and weight-based titration; source of paediatric vs adolescent half-life and apparent volume-of-distribution data cited above.
- Swearingen D, Pennick M, Shojaei A, Lyne A, Fiske K. A phase I, randomized, open-label, crossover study of the single-dose pharmacokinetic properties of guanfacine extended-release 1-, 2-, and 4-mg tablets in healthy adults. Clin Ther. 2007;29(4):617–625. doi:10.1016/j.clinthera.2007.04.001 Adult PK comparison across XR strengths informing food-effect and bioavailability discussions.