Guanfacine Hcl Er (guanfacine HCl)
Central Adrenolytics Oral Tablet, Extended Release 24 Hr
Last reviewed · Source: First Databank (FDB) drug data
Overview
Guanfacine is a phenylacetyl-guanidine derivative hypotensive agent; the drug is a selective alpha2-adrenergic agonist.
Guanfacine appears to stimulate alpha2-adrenergic receptors in the CNS, causing inhibition of sympathetic vasomotor centers; this contributes predominantly to the hypotensive effects of the drug. Central effects of the drug result in reduced peripheral sympathetic nerve impulses from the vasomotor center to the heart and blood vessels, resulting in a decrease in peripheral vascular resistance and a reduction in heart rate. Under conditions of rest or exercise, cardiac output is not altered.
Guanfacine reduces blood pressure in both supine and standing positions; hypotensive effects may be somewhat greater in the standing position. Peripheral effects (stimulation of peripheral alpha2-adrenergic receptors) also may contribute to the drug's hypotensive effects.
Guanfacine lowers elevated plasma renin activity and plasma catecholamine concentrations in patients with hypertension, although these effects do not correlate with individual hypotensive responses.
Acute administration of guanfacine stimulates release of growth hormone, but the drug does not produce sustained elevation of growth hormone during chronic administration. Guanfacine does not affect plasma aldosterone, mean body weight, or electrolytes; a slight but insignificant increase in plasma volume is observed after 1 month of therapy. The drug reduces serum prolactin concentrations in hypertensive patients with elevated serum prolactin concentrations.
Guanfacine enhances neurologic activity in the prefrontal cortex, an area of the brain involved in planning, impulse control, and organization. The drug has been shown in nonhuman primates to improve prefrontal cortical function through direct action on postsynaptic alpha2A-adrenergic receptors located in the prefrontal cortex. Sedative effects, which are less severe than those seen with clonidine, are the result of inhibitory effects on noradrenergic locus ceruleus neurons and direct effects on the thalamus.
USES: This medication is used to treat attention deficit hyperactivity disorder (ADHD), as part of a total treatment plan including psychological, educational, and social measures. Unlike other drugs used to treat ADHD, guanfacine is not a stimulant. The exact way that guanfacine works to treat ADHD is unknown.
Guanfacine is thought to affect receptors in the parts of the brain that lead to strengthening working memory, reducing distraction, and improving attention and impulse control. Guanfacine may help lessen ADHD symptoms such as being disruptive, inattentive, hyperactive, impulsive, and arguing with adults or losing one's temper.
Generic name: guanfacine HCl
Pronunciation: (GWAN-fuh-seen)
Drug class: Central Adrenolytics
Therapeutic class: Central Nervous System Agents
Reference product & biosimilars
No reference, biosimilar or interchangeable associated with this drug.
Today’s intelligence on Guanfacine Hcl Er
Indications
The following indications are listed for Guanfacine Hcl Er:
- Attention-Deficit Hyperactivity Disorder
Also known as: Add With Hyperactivity.
Dosing
Dosage of guanfacine hydrochloride is expressed in terms of guanfacine.
No dosing information is available for this tab.
No dosing information is available for this tab.
No dosing information is available for this tab.
Drug interactions
There is no enhanced messaging for this drug.
There are no contraindication interactions for this drug.
Severe Interaction: Action is required to reduce the risk of severe adverse interaction.
Alpha-2 Agonists/Tizanidine
SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.
MECHANISM OF ACTION: Tizanidine is an alpha-2 agonist. Concurrent use with other alpha-2 agonists may result in additive effects on blood pressure.(1)
CLINICAL EFFECTS: Concurrent use of alpha-2 agonists and tizanidine may result in hypotension.(1)
PREDISPOSING FACTORS: None determined.
PATIENT MANAGEMENT: The manufacturer of tizanidine states concurrent use with other alpha-2 agonists is not recommended.(1) Patients receiving concurrent therapy should be monitored for hypotension. The risk of hypotension may be decreased by careful titration of tizanidine dosages and monitoring for hypotension prior to dose advancement. Counsel patients about the risk of orthostatic hypotension.(1)
DISCUSSION: Severe hypotension has been reported following the addition of tizanidine to existing lisinopril therapy.(2-4) Alpha-2 agonists linked include: clonidine, dexmedetomidine, guanabenz, guanadrel, guanethidine, guanfacine, methyldopa, and moxonidine.
Guanfacine/Strong & Moderate Cyp3a4 Inducers
SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.
MECHANISM OF ACTION: Strong or moderate inducers of CYP3A4 may induce the metabolism of guanfacine.(1)
CLINICAL EFFECTS: The concurrent administration of a strong or moderate CYP3A4 inducer may result in decreased levels and effectiveness of guanfacine.(1)
PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.
PATIENT MANAGEMENT: Patients maintained on guanfacine may need dosage adjustments if strong or moderate inducers of CYP3A4 are initiated or discontinued. The manufacturer of extended-release guanfacine recommends a starting dose of extended-release guanfacine initiated at up to double the recommended level of the weight based dosing in patients receiving strong or moderate inducers of CYP3A4. If a patient has been maintained on extended-release guanfacine and is started on a strong or moderate CYP3A4 inducer, the dose of extended-release guanfacine should be increased up to double the recommended weight based dose over 1 to 2 weeks. If a patient has been maintained on extended-release guanfacine and a strong or moderate CYP3A4 inducer, and the strong or moderate CYP3A4 inducer is discontinued, the dose of extended-release guanfacine may need to be decreased to the recommended weight based dose over 1 to 2 weeks. Extended-release guanfacine target dose range for attention deficit hyperactivity disorder is 0.05-0.12 mg/kg/day. Doses above 4 mg/day have not been evaluated in children ages 6-12 years and doses above 7 mg/day have not been evaluated in adolescents ages 13-17 years.(1)
DISCUSSION: Rifampin (dosage not stated), a strong inducer of CYP3A4, decreased the maximum concentration (Cmax) and area-under-curve (AUC) of guanfacine (dosage not stated) by approximately 50%.(1) Strong inducers of CYP3A4 include: apalutamide, barbiturates, carbamazepine, encorafenib, enzalutamide, fosphenytoin, ivosidenib, lumacaftor, mitotane, phenobarbital, phenytoin, primidone, rifabutin, rifampin, rifapentine, and St. John's wort.(1-3) Moderate inducers of CYP3A4 include: belzutifan, bosentan, cenobamate, dabrafenib, efavirenz, elagolix, etravirine, fexinidazole, lesinurad, lorlatinib, mavacamten, mitapivat, modafinil, nafcillin, pacritinib, pexidartinib, repotrectinib, sotorasib, telotristat, thioridazine, and tovorafenib.(1-3)
Guanfacine/Strong & Moderate Cyp3a4 Inhibitors
SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.
MECHANISM OF ACTION: Strong or moderate inhibitors of CYP3A4 may inhibit the metabolism of guanfacine.(1)
CLINICAL EFFECTS: The concurrent administration of a strong or moderate CYP3A4 inhibitor may result in elevated levels of guanfacine, which may result in increased adverse effects such as hypotension, bradycardia, loss of consciousness, and drowsiness.(1)
PREDISPOSING FACTORS: None determined.
PATIENT MANAGEMENT: Patients maintained on guanfacine may need dosage adjustments if strong or moderate inhibitors of CYP3A4 are initiated or discontinued. The manufacturer of extended-release guanfacine recommends a starting dose of extended-release guanfacine initiated at half the recommended level of the weight based dosing in patients receiving strong or moderate inhibitors of CYP3A4. If a patient has been maintained on extended-release guanfacine and is started on a strong or moderate CYP3A4 inhibitor, the dose of extended-release guanfacine should be decreased to half the recommended weight based dose. If a patient has been maintained on extended-release guanfacine and a strong or moderate CYP3A4 inhibitor and the strong or moderate CYP3A4 inhibitor is discontinued, the dose of extended-release guanfacine may need to be increased to the recommended weight based dose based upon patient response. Extended-release guanfacine target dose range for attention deficit hyperactivity disorder is 0.05-0.12 mg/kg/day. Doses above 4 mg/day have not been evaluated in children ages 6-12 years and doses above 7 mg/day have not been evaluated in adolescents ages 13-17 years.(1)
DISCUSSION: Ketoconazole (dosage not stated), a strong inhibitor of CYP3A4, increased the maximum concentration (Cmax) and area-under-curve (AUC) of guanfacine (dosage not stated) by approximately 1.75-fold and 3-fold, respectively.(1) Strong inhibitors of CYP3A4 include: adagrasib, boceprevir, ceritinib, clarithromycin, cobicistat, ensitrelvir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, levoketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, posaconazole, relacorilant, ribociclib, ritonavir, saquinavir, telaprevir, telithromycin, tipranavir, troleandomycin, tucatinib, and voriconazole.(1-3) Moderate inhibitors of CYP3A4 include: amprenavir, aprepitant, atazanavir, avacopan, berotralstat, clofazimine, conivaptan, crizotinib, darunavir, diltiazem, dronedarone, duvelisib, erythromycin, fedratinib, fluconazole, fluvoxamine, fosnetupitant, imatinib, isavuconazonium, lenacapavir, letermovir, netupitant, nilotinib, rilzabrutinib, schisandra, stiripentol, tofisopam, treosulfan and verapamil.(1-3)
Moderate Interaction: Assess the risk to the patient and take action as needed.
Selected Antihypertensives And Vasodilators/Apomorphine
SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.
MECHANISM OF ACTION: Apomorphine causes dose-dependent decreases in blood pressure. Concurrent use with antihypertensive agents may result in additive effects on blood pressure.(1)
CLINICAL EFFECTS: Concurrent use of antihypertensives and apomorphine may result in orthostatic hypotension with or without dizziness, nausea, or syncope.(1)
PREDISPOSING FACTORS: The risk of orthostatic hypotension may be increased during dose escalation of apomorphine and in patients with renal or hepatic impairment.(1)
PATIENT MANAGEMENT: Patients receiving concurrent therapy should be monitored for hypotension. Counsel patients about the risk of orthostatic hypotension.(1)
DISCUSSION: Healthy volunteers who took sublingual nitroglycerin (0.4 mg) concomitantly with apomorphine experienced a mean largest decrease in supine systolic blood pressure (SBP) of 9.7 mm Hg and in supine diastolic blood pressure (DBP) of 9.3 mm Hg, and a mean largest decrease in standing SBP and DBP of 14.3 mm Hg and 13.5 mm Hg, respectively. The maximum decrease in SBP and DBP was 65 mm Hg and 43 mm Hg, respectively. When apomorphine was taken alone, the mean largest decrease in supine SBP and DBP was 6.1 mm Hg and 7.3 mm Hg, respectively, and in standing SBP and DBP was 6.7 mm Hg and 8.4 mm Hg, respectively.(1)
Contraindications
Guanfacine is contraindicated in patients with known hypersensitivity to the drug.
There are no contraindication contraindications for this drug.
- Bradycardia
- Hypotension
- Suicidal ideation
- Aggressive behavior
- Alcohol intoxication
- Disease of liver
- Drowsy
- Kidney disease with reduction in glomerular filtration rate (GFr)
- Orthostatic hypotension
Adverse reactions
Common adverse effects in patients receiving guanfacine include dry mouth, somnolence, dizziness, constipation, fatigue, asthenia, impotence, and headache.
Rare or Very Rare
- Atrioventricular block
- Bradycardia
- Chest pain
- Encephalopathy
- Exfoliative dermatitis
- Hypersensitivity drug reaction
- Seizure disorder
- Sinus node dysfunction
- Suicidal
- Suicidal ideation
- Tachycardia
More Frequent
- Acute abdominal pain
- Dizziness
- Drowsy
- Fatigue
- Hypotension
- Insomnia
- Lethargy
- Nausea
- Sedation
- Weight gain
- Xerostomia
Less Frequent
- Acute cognitive impairment
- Anorexia
- Constipation
- Dyspepsia
- Erectile dysfunction
- General weakness
- Headache disorder
- Increased urinary frequency
- Irritability
- Libido changes
- Nightmares
- Palpitations
- Pruritus of skin
- Urinary incontinence
- Vomiting
Rare or Very Rare
- Accidental fall
- Alopecia
- Arthralgia
- Blurred vision
- Conjunctivitis
- Cramps in legs
- Depression
- Dysgeusia
- Dyspnea
- Edema
- Hallucinations
- Malaise
- Myalgia
- Pallor
- Paresthesia
- Raynaud's phenomenon
- Skin inflammation
- Skin rash
- Symptoms of anxiety
- Syncope
- Tremor
- Vertigo
Precautions
No enhanced messaging available.
Safety and efficacy of guanfacine for the management of hypertension have not been established in children younger than 12 years of age; use in these pediatric patients is not recommended.
Mania and aggressive behavioral changes have been reported in pediatric patients with ADHD receiving guanfacine (as conventional tablets)+; all patients had medical or family risk factors for bipolar disorder. All patients recovered following discontinuance of the drug.
Category B. (See Users Guide.)
Guanfacine is not recommended for the treatment of acute hypertension associated with toxemia of pregnancy.
Guanfacine is distributed into milk in rats; it is not known whether the drug is distributed into human milk. Caution is advised if guanfacine is used in nursing women.
Guanfacine dosage should be selected with caution (usually starting at the low end of the dosing range) because of age-related decreases in hepatic, renal, and/or cardiac function and concomitant disease and drug therapy.
Clinical trial data for patients 65 years of age or older are insufficient to determine whether geriatric patients respond differently than younger adults. Other experience suggests that response is similar to that in younger adults.
Dosage of guanfacine should be selected with caution because of age-related decreases in hepatic, renal, and/or cardiac function and potential for concomitant disease and drug therapy.
ICD codes
| Code | Type | Description |
|---|---|---|
| Attention-deficit hyperactivity disorder | ||
| F90 | ICD10CM | Attention-deficit hyperactivity disorders |
| F90.0 | ICD10CM | Attention-deficit hyperactivity disorder, predominantly inattentive type |
| F90.1 | ICD10CM | Attention-deficit hyperactivity disorder, predominantly hyperactive type |
| F90.2 | ICD10CM | Attention-deficit hyperactivity disorder, combined type |
| F90.8 | ICD10CM | Attention-deficit hyperactivity disorder, other type |
| F90.9 | ICD10CM | Attention-deficit hyperactivity disorder, unspecified type |
ICD code information from First Databank (FDB).
Formulary status
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Last reviewed · Source: First Databank (FDB) drug data
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