(GWAHN fa seen)
Attention-deficit/hyperactivity disorder (extended release only): Treatment of attention-deficit/hyperactivity disorder (ADHD) as monotherapy and as adjunctive therapy to stimulant medications.
Hypertension (immediate release only): Management of hypertension.
Hypersensitivity to guanfacine or any component of the formulation
Hypertension: Immediate release: Oral: 1 mg once daily at bedtime, may increase if needed after 3 to 4 weeks of therapy to 2 mg daily at bedtime. Note: Adverse reactions increase significantly with doses above 3 mg/day.
Immediate release: Refer to adult dosing. In the management of hypertension, consider lower initial doses and titrate to response (Aronow 2011).
ADHD: Extended release: Children ≥6 years and Adolescents ≤17 years: Oral: Initial: 1 mg once daily; may adjust by increments of no more than 1 mg/week. Recommended target dose is 0.05 to 0.12 mg/kg/dose (1 to 7 mg) once daily, depending on clinical response and tolerability.
Maximum daily doses: Doses above the following have not been evaluated.
Monotherapy: Children 6 to 12 years: 4 mg/day; Adolescents: 13 to 17 years: 7 mg/day
Adjunct therapy (with psychostimulants): 4 mg/day
Suggested fixed target dose range for patients weighing ≥25 kg: All doses administered once daily at the same time (either in the morning or evening) not to exceed age-based maximum daily doses.
25 to 33.9 kg: 2 to 3 mg/day
34 to 41.4 kg: 2 to 4 mg/day
41.5 to 49.4 kg: 3 to 5 mg/day
49.5 to 58.4 kg: 3 to 6 mg/day
58.5 to 91 kg: 4 to 7 mg/day
>91 kg: 5 to 7 mg/day
Dosage adjustment for concomitant CYP3A4 inhibitors/inducers:
Strong CYP3A4 inhibitors: If initiating guanfacine while taking a strong CYP3A4 inhibitor or if continuing guanfacine and adding a strong CYP3A4 inhibitor, decrease guanfacine dose by 50%. If continuing guanfacine and discontinuing the strong CYP3A4 inhibitor, increase guanfacine to the recommended dose.
Strong CYP3A4 inducers: If initiating guanfacine while taking a strong CYP3A4 inducer, consider increasing guanfacine to double the recommended dose. If continuing guanfacine and adding a strong CYP3A4 inducer, consider increasing guanfacine gradually over 1 to 2 weeks to double the recommended dose. If continuing guanfacine and discontinuing the strong CYP3A4 inducer, gradually decrease guanfacine dose to the recommended dose over 1 to 2 weeks.
Conversion from immediate release to extended release: Discontinue the immediate release formulation, and titrate according to extended release recommendations.
Missed doses of extended release: If ≥2 consecutive doses are missed, consider repeating dosage titration based on patient tolerability.
Discontinuation of extended release: Gradually discontinue by tapering dose in decrements of ≤1 mg every 3 to 7 days to avoid rebound hypertension.
Hypertension: Children ≥12 years and Adolescents: Immediate release: Oral: Refer to adult dosing.
Tourette syndrome (off-label use): Children ≥6 years and Adolescents ≤16 years: Immediate release: Oral: Initial: 0.5 mg once daily at bedtime for 3 days, then 0.5 mg twice daily for 4 days, then 0.5 mg 3 times daily; may further increase dose after 7 days based on clinical response to maximum daily dose of 4 mg/day in 3 divided doses (Scahill 2001); twice daily dosing may be effective for some patients (Chappell, 1995; Cummings 2002). Note: Limited data available; greater efficacy shown in patients with ADHD comorbidity (AACAP [Murphy 2013]; ESSTS [Roessner 2011]; Pringsheim 2012; Weisman 2013).
Immediate release: Children ≥12 years, Adolescents, and Adults: There are no specific dosage adjustments provided in the manufacturer 's labeling; however, the lower end of the dosing range is recommended in patients with renal impairment.
Extended release: Children ≥6 years and Adolescents ≤17 years: There are no dosage adjustments provided in the manufacturer 's labeling (has not been studied); however, dosage adjustments may be necessary in patients with significant renal impairment.
Hemodialysis: Immediate release or extended release: Dialysis clearance is low (~15% of total clearance).
Immediate release: Children ≥12 years, Adolescents, and Adults: There are no dosage adjustments provided in the manufacturer 's labeling; however, use with caution in chronic hepatic impairment.
Extended release: Children ≥6 years and Adolescents ≤17 years: There are no dosage adjustments provided in the manufacturer 's labeling (has not been studied); however, dosage adjustments may be necessary in patients with significant hepatic impairment.
Immediate-release tablets are usually given at bedtime to minimize somnolence. Extended-release tablets should be taken at the same time each day (either morning or evening), and should not be crushed, broken, or chewed. Do not administer ER tablets with a high-fat meal because of increased exposure. Formulations (immediate release versus extended release) are not interchangeable.
Extended-release tablets: Do not administer with a high-fat meal due to increased exposure.
Immediate release: Store at 20 ‚ °C to 25 ‚ °C (68 ‚ °F to 77 ‚ °F).
Extended release: Store at 20 ‚ °C to 25 ‚ °C (68 ‚ °F to 77 ‚ °F); excursions permitted between 15 ‚ °C and 30 ‚ °C (59 ‚ °F and 86 ‚ °F).
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Tenex: 1 mg [contains fd&c red #40 aluminum lake]
Tenex: 2 mg [contains fd&c yellow #10 aluminum lake]
Generic: 1 mg, 2 mg
Tablet Extended Release 24 Hour, Oral:
Intuniv: 1 mg, 2 mg, 3 mg, 4 mg
Generic: 1 mg, 2 mg, 3 mg, 4 mg
Alcohol (Ethyl): May enhance the CNS depressant effect of GuanFACINE. Avoid combination
Alfuzosin: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, blood pressure lowering medications should be withheld for 24 hours prior to amifostine administration. If blood pressure lowering therapy cannot be withheld, amifostine should not be administered. Consider therapy modification
Amphetamines: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]). Monitor therapy
Azelastine (Nasal): CNS Depressants may enhance the CNS depressant effect of Azelastine (Nasal). Avoid combination
Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Beta-Blockers: Alpha2-Agonists may enhance the AV-blocking effect of Beta-Blockers. Sinus node dysfunction may also be enhanced. Beta-Blockers may enhance the rebound hypertensive effect of Alpha2-Agonists. This effect can occur when the Alpha2-Agonist is abruptly withdrawn. Management: Closely monitor heart rate during treatment with a beta blocker and clonidine. Withdraw beta blockers several days before clonidine withdrawal when possible, and monitor blood pressure closely. Recommendations for other alpha2-agonists are unavailable. Exceptions: Levobunolol; Metipranolol. Consider therapy modification
Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Consider therapy modification
Bradycardia-Causing Agents: May enhance the bradycardic effect of other Bradycardia-Causing Agents. Monitor therapy
Bretylium: May enhance the bradycardic effect of Bradycardia-Causing Agents. Bretylium may also enhance atrioventricular (AV) blockade in patients receiving AV blocking agents. Monitor therapy
Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine patches (Butrans brand) at 5 mcg/hr in adults when used with other CNS depressants. Consider therapy modification
Cannabis: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Ceritinib: Bradycardia-Causing Agents may enhance the bradycardic effect of Ceritinib. Management: If this combination cannot be avoided, monitor patients for evidence of symptomatic bradycardia, and closely monitor blood pressure and heart rate during therapy. Avoid combination
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Monitor therapy
Conivaptan: May increase the serum concentration of CYP3A4 Substrates. Avoid combination
CYP3A4 Inducers (Moderate): May decrease the serum concentration of GuanFACINE. Management: Increase the guanfacine dose by up to double when initiating concomitant therapy with moderate CYP3A4 inducers. Increase guanfacine dose gradually over 1-2 weeks if moderate CYP3A4 inducer therapy is just beginning. Consider therapy modification
CYP3A4 Inducers (Strong): May decrease the serum concentration of GuanFACINE. Management: Increase the guanfacine dose by up to double when initiating concomitant therapy with strong CYP3A4 inducers. Increase guanfacine dose gradually over 1-2 weeks if strong CYP3A4 inducer therapy is just beginning. Consider therapy modification
CYP3A4 Inhibitors (Moderate): May increase the serum concentration of GuanFACINE. Management: Reduce the guanfacine dose by 50% when initiating this combination. Consider therapy modification
CYP3A4 Inhibitors (Strong): May increase the serum concentration of GuanFACINE. Management: Reduce the guanfacine dose by 50% when initiating this combination. Consider therapy modification
Dabrafenib: May decrease the serum concentration of CYP3A4 Substrates. Management: Seek alternatives to the CYP3A4 substrate when possible. If concomitant therapy cannot be avoided, monitor clinical effects of the substrate closely (particularly therapeutic effects). Consider therapy modification
Dasatinib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy
Deferasirox: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy
Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Dimethindene: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended. Monitor therapy
Dronabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (e.g., opioids, barbiturates) with concomitant use. Consider therapy modification
DULoxetine: Blood Pressure Lowering Agents may enhance the hypotensive effect of DULoxetine. Monitor therapy
Enzalutamide: May decrease the serum concentration of CYP3A4 Substrates. Management: Concurrent use of enzalutamide with CYP3A4 substrates that have a narrow therapeutic index should be avoided. Use of enzalutamide and any other CYP3A4 substrate should be performed with caution and close monitoring. Consider therapy modification
Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Consider therapy modification
Fosaprepitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy
Fusidic Acid (Systemic): May increase the serum concentration of CYP3A4 Substrates. Avoid combination
Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
Herbs (Hypotensive Properties): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
HYDROcodone: CNS Depressants may enhance the CNS depressant effect of HYDROcodone. Management: Consider starting with a 20% to 30% lower hydrocodone dose when using together with any other CNS depressant. Dose reductions in the other CNS depressant may also be warranted. Consider therapy modification
HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Monitor therapy
Idelalisib: May increase the serum concentration of CYP3A4 Substrates. Avoid combination
Iobenguane I 123: Alpha2-Agonists may diminish the therapeutic effect of Iobenguane I 123. Avoid combination
Ivabradine: Bradycardia-Causing Agents may enhance the bradycardic effect of Ivabradine. Monitor therapy
Ivacaftor: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy
Kava Kava: May enhance the adverse/toxic effect of CNS Depressants. Monitor therapy
Lacosamide: Bradycardia-Causing Agents may enhance the AV-blocking effect of Lacosamide. Monitor therapy
Levodopa: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa. Monitor therapy
Luliconazole: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy
Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce adult dose of CNS depressant agents by 50% with initiation of concomitant methotrimeprazine therapy. Further CNS depressant dosage adjustments should be initiated only after clinically effective methotrimeprazine dose is established. Consider therapy modification
Methylphenidate: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
MetyroSINE: CNS Depressants may enhance the sedative effect of MetyroSINE. Monitor therapy
MiFEPRIStone: May increase the serum concentration of CYP3A4 Substrates. Management: Minimize doses of CYP3A4 substrates, and monitor for increased concentrations/toxicity, during and 2 weeks following treatment with mifepristone. Avoid cyclosporine, dihydroergotamine, ergotamine, fentanyl, pimozide, quinidine, sirolimus, and tacrolimus. Consider therapy modification
Minocycline: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Mirtazapine: May diminish the antihypertensive effect of Alpha2-Agonists. Management: Consider avoiding concurrent use. If the combination cannot be avoided, monitor for decreased effects of alpha2-agonists if mirtazapine is initiated/dose increased, or increased effects if mirtazapine is discontinued/dose decreased. Consider therapy modification
Mitotane: May decrease the serum concentration of CYP3A4 Substrates. Management: Doses of CYP3A4 substrates may need to be adjusted substantially when used in patients being treated with mitotane. Consider therapy modification
Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Nabilone: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Naftopidil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Nicergoline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Nitroprusside: Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside. Monitor therapy
Obinutuzumab: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Consider therapy modification
Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Avoid combination
Osimertinib: May increase the serum concentration of CYP3A4 Substrates. Osimertinib may decrease the serum concentration of CYP3A4 Substrates. Monitor therapy
OxyCODONE: CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: When oxycodone is combined with another CNS depressant, a dose reduction of one or both agents should be considered. The extended release oxycodone starting dose should be reduced 50% to 67% when initiated in patients already receiving CNS depressants. Consider therapy modification
Palbociclib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy
Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Avoid combination
Pentoxifylline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Perampanel: May enhance the CNS depressant effect of CNS Depressants. Management: Patients taking perampanel with any other drug that has CNS depressant activities should avoid complex and high-risk activities, particularly those such as driving that require alertness and coordination, until they have experience using the combination. Consider therapy modification
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Piribedil [INT]: CNS Depressants may enhance the CNS depressant effect of Piribedil [INT]. Monitor therapy
Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Monitor therapy
Prostacyclin Analogues: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Quinagolide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Monitor therapy
Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Monitor therapy
Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Monitor therapy
Ruxolitinib: May enhance the bradycardic effect of Bradycardia-Causing Agents. Management: Ruxolitinib Canadian product labeling recommends avoiding use with bradycardia-causing agents to the extent possible. Monitor therapy
Selective Serotonin Reuptake Inhibitors: CNS Depressants may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors. Specifically, the risk of psychomotor impairment may be enhanced. Monitor therapy
Serotonin/Norepinephrine Reuptake Inhibitors: May diminish the antihypertensive effect of Alpha2-Agonists. Monitor therapy
Siltuximab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy
Simeprevir: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy
Sodium Oxybate: May enhance the CNS depressant effect of CNS Depressants. Management: Consider alternatives to combined use. When combined use is needed, consider minimizing doses of one or more drugs. Use of sodium oxybate with alcohol or sedative hypnotics is contraindicated. Consider therapy modification
St Johns Wort: May decrease the serum concentration of GuanFACINE. Management: Consider increasing the guanfacine dose by 2-fold when adding St Johns Wort. Titrate the guanfacine dose up to a max of 8 mg/day when starting guanfacine in a patient who is taking St Johns Wort. Consider therapy modification
Stiripentol: May increase the serum concentration of CYP3A4 Substrates. Management: Use of stiripentol with CYP3A4 substrates that are considered to have a narrow therapeutic index should be avoided due to the increased risk for adverse effects and toxicity. Any CYP3A4 substrate used with stiripentol requires closer monitoring. Consider therapy modification
Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Consider therapy modification
Tapentadol: May enhance the CNS depressant effect of CNS Depressants. Management: Start tapentadol at a dose of one-third to one-half of the normal dose if being initiated in a patient who is taking another drug with CNS depressant effects. Monitor closely for evidence of excessive CNS depression. Consider therapy modification
Tetrahydrocannabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Avoid combination
Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy
Tofacitinib: May enhance the bradycardic effect of Bradycardia-Causing Agents. Monitor therapy
Tricyclic Antidepressants: May diminish the antihypertensive effect of Alpha2-Agonists. Consider therapy modification
Trimeprazine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy
Valproate Products: GuanFACINE may increase the serum concentration of Valproate Products. Monitor therapy
Yohimbine: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Consider therapy modification
Heart rate, blood pressure
When used for the treatment of ADHD, thoroughly evaluate for cardiovascular risk. Monitor heart rate, blood pressure (prior to initiation, following dosage adjustments, and periodically thereafter), and consider obtaining ECG prior to initiation (Vetter 2008).
>10%:
Central nervous system: Drowsiness (10% to 57%; dose-related), headache (4% to 28%), fatigue (5% to 22%), dizziness (4% to 16%; dose-related), insomnia (2% to 13%),
Gastrointestinal: Xerostomia (3% to 54%; dose-related), abdominal pain ( ≤8% to 19%; dose-related), decreased appetite (5% to 15%), constipation (2% to 15%; dose-related)
1% to 10%:
Cardiovascular: Hypotension ( ≤1% to 9%; dose-related; includes orthostatic), bradycardia (2% to 5%), atrioventricular block ( ≥2%), sinus arrhythmia ( ≥2%), syncope (1% to ≥2%)
Central nervous system: Irritability (5% to 8%), lethargy (3% to 8%), anxiety (2% to 5%), nightmares (3% to 4%), emotional lability (children and adolescents 6 to 17 years: 2% to 3%), agitation ( ≥2%), depression ( ≥2%)
Dermatologic: Skin rash (2% to 3%), pruritus (2%)
Endocrine & metabolic: Weight gain ( ≤2% to 3%)
Gastrointestinal: Nausea ( ≤5% to 7%), vomiting (2% to 7%), diarrhea (2% to 6%), dyspepsia ( ≥2%), stomach pain ( ≥2%)
Genitourinary: Impotence ( ≤3% to 7%), urinary incontinence (2% to 5%)
Neuromuscular & skeletal: Weakness ( ≤2% to 7%)
Respiratory: Asthma ( ≥2%)
Miscellaneous: Fever (8%; Biederman 2008)
Frequency not defined:
Cardiovascular: Chest pain, hypertension
Central nervous system: Convulsions
Dermatologic: Pallor
Genitourinary: Urinary frequency
Hepatic: Increased serum ALT
Hypersensitivity: Hypersensitivity reaction
<1% (Limited to important or life-threatening): Alopecia, amnesia, cardiac fibrillation, cerebrovascular accident, dermatitis, dysphagia, exacerbation of cardiac disease (sinus node dysfunction, atrioventricular block), exfoliative dermatitis, hallucination, hypertensive encephalopathy (with abrupt discontinuation), hypokinesia, iritis, mania (immediate release; children), myocardial infarction, nocturia, palpitations, paresis, Raynaud phenomenon, rebound hypertension, renal failure, tachycardia, visual disturbance
In patients with renal impairment, clearance is reduced; plasma levels are only slightly increased. In patients on hemodialysis, dialysis clearance was ~15% of total clearance.
Exposure to guanfacine was higher in children (6 to 12 years of age) compared with adolescents (13 to 17 years of age).
Concerns related to adverse effects:
- Cardiovascular effects: May cause atrioventricular (AV) block, bradycardia, hypotension, orthostasis, sinus node dysfunction, and syncope; these effects are dose-dependent, more pronounced during the first month of therapy, or may worsen especially when used with other sympatholytic drugs. Monitor vital signs frequently in patients with cardiac conduction abnormalities or those concomitantly treated with other sympatholytic drugs.
- CNS effects: May cause sedation and drowsiness which may impair physical or mental abilities; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery, driving).
- Dermatological effects: Skin rash with exfoliation and pruritus have been reported; discontinue guanfacine and monitor patients who develop a rash.
Disease-related concerns:
- Cardiovascular disease: Use with caution in patients with severe coronary insufficiency, recent MI, or a history of bradycardia, cardiovascular disease, heart block, hypotension, or syncope. Cautious use is also recommended in patients with conditions that predispose them to syncope (eg, orthostasis, dehydration).
- Cerebrovascular disease: Use with caution in patients with cerebrovascular disease.
- Hepatic impairment: Use with caution in patients with chronic hepatic impairment. Dosage adjustment may be necessary in severe impairment.
- Renal impairment: Use with caution in patients with chronic renal impairment. Dosage adjustment may be necessary in severe impairment.
Concurrent drug therapy issues:
- Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.
Dosage form specific issues:
- Product interchangeability: Formulations of guanfacine (immediate release versus extended release) are not interchangeable on a mg to mg basis because bioavailability, Cmax, and Tmax vary.
Other warnings/precautions:
- Discontinuation of therapy: Blood pressure and pulse may increase following discontinuation of therapy. Abrupt discontinuation can result in nervousness and anxiety; rarely, rebound hypertension (occurs 2 to 4 days after withdrawal) and hypertensive encephalopathy have also been reported. To minimize these effects, taper the dose in decrements of ≤1 mg every 3 to 7 days and monitor blood pressure and pulse following dosage reduction/discontinuation.
- ADHD treatment: Appropriate use: Recommended to be used as part of a comprehensive treatment program for attention-deficit disorders; safety and efficacy of long-term use for the treatment of ADHD (>2 years) have not been established (Sallee 2009).
B
Adverse events have not been observed in animal reproduction studies except in doses that also caused maternal toxicity. Information related to guanfacine use during pregnancy is limited (Philipp 1980). Untreated chronic maternal hypertension is associated with adverse events in the fetus, infant, and mother. If treatment for hypertension during pregnancy is needed, other agents are preferred (ACOG 2012).
Guanfacine is a selective alpha2A-adrenoreceptor agonist that reduces sympathetic nerve impulses, resulting in reduced sympathetic outflow and a subsequent decrease in vasomotor tone and heart rate. In addition, guanfacine preferentially binds postsynaptic alpha2A-adrenoreceptors in the prefrontal cortex and has been theorized to improve delay-related firing of prefrontal cortex neurons. As a result, underlying working memory and behavioral inhibition are affected; thereby improving symptoms associated with ADHD. Guanfacine is not a CNS stimulant.
Readily absorbed.
Vd: Immediate release: 6.3 L/kg; Extended release: Vd (apparent): Children ≥6 years: 23.7 L/kg; Adolescent: 19.9 L/kg (Boellner 2007)
Hepatic via CYP3A4. Approximately 50% of clearance is hepatic.
Urine (~50% [40% to 75% of dose] as unchanged drug)
Serum:
Immediate release: 2.6 hours (range: 1 to 4 hours)
Extended release: Children ≥6 years and Adolescents: 5 hours (Boellner 2007); Adults: 4 to 8 hours
Antihypertensive effect: 24 hours following single dose
Immediate release: ~17 hours (range: 10 to 30 hours)
Extended release: Children ≥6 years: 14.4 hours; Adolescents: 18 hours (Boellner 2007); Adults: 16 hours
~70%
- Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
- Patient may experience constipation, dry mouth, loss of strength and energy, irritability, nausea, vomiting, insomnia, abdominal pain, lack of appetite, or headache. Have patient report immediately to prescriber severe dizziness, passing out, bradycardia, arrhythmia, severe fatigue, or sexual dysfunction (HCAHPS).
- Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.
Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.