Guanfacine Side Effects

Medically reviewed by Drugs.com. Last updated on Apr 24, 2024.

Applies to guanfacine: oral tablet, oral tablet extended release.

Serious side effects of guanfacine

Along with its needed effects, guanfacine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking guanfacine:

More common side effects

• blurred vision
• confusion
• dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
• sweating
• unusual tiredness or weakness

Less common side effects

• chest pain or discomfort
• cough
• difficulty with breathing
• fast, slow, pounding, or irregular heartbeat
• increased need to urinate
• lightheadedness, dizziness, or fainting
• mental depression
• noisy breathing
• passing urine more often
• tightness in the chest

Incidence not known

• agitation
• back pain
• cracks in the skin
• drowsiness
• fast, pounding, or irregular pulse
• feeling of constant movement of self or surroundings
• fever
• headache
• irritability
• loss of consciousness
• loss of heat from the body
• mood or mental changes
• numbness or tingling in the arms, legs, or face
• red, swollen skin
• scaly skin
• seeing or hearing things that are not there
• seizures
• sensation of spinning
• stiff neck
• swelling
• vomiting
• weakness

Get emergency help immediately if any of the following symptoms of overdose occur while taking guanfacine:

Symptoms of overdose

• dizziness (extreme) or faintness
• unusual tiredness or weakness (severe)

Other side effects of guanfacine

Some side effects of guanfacine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common side effects

• constipation
• dizziness
• dryness of the mouth
• nausea
• sleepiness or unusual drowsiness
• unusual dullness or feeling of sluggishness
• upper abdominal or stomach pain
• weight gain

Less common side effects

• belching
• decreased appetite
• decreased sexual ability
• dry, itching, or burning eyes
• heartburn
• indigestion
• lack or loss of strength
• paleness of the skin
• stomach discomfort, upset, or pain
• trouble with sleeping

Incidence not known

• change in taste
• decreased interest in sexual intercourse
• difficulty in moving
• general feeling of discomfort or illness
• hair loss, thinning of hair
• inability to have or keep an erection
• joint pain or swelling
• leg cramp or pain
• loss in sexual ability, desire, drive, or performance
• muscle ache, cramp, pain, or stiffness
• seeing or hearing things that are not there

After you stop using this medicine, it may still produce some side effects that need attention. During this period of time, Check with your doctor immediately if you notice the following side effects:

• anxiety or tenseness
• increased salivation
• nervousness or restlessness
• shaking or trembling of the hands and fingers
• stomach cramps
• sweating

For healthcare professionals

Applies to guanfacine: oral tablet, oral tablet extended release.

General adverse events

The most common adverse reactions were dry mouth, somnolence, headache, fatigue, dizziness, abdominal pain, constipation, appetite decreased, and sedation.^[Ref]

Gastrointestinal

• Very common (10% or more): Dry mouth (up to 54%), abdominal pain (up to 15%), constipation (up to 15%)
• Common (1% to 10%): Vomiting, diarrhea, nausea, abdominal/stomach discomfort
• Uncommon (0.1% to 1%): Dyspepsia^[Ref]

Nervous system

• Very common (10% or more): Somnolence (up to 40.6%), headache (up to 28%), dizziness (up to 16%), sedation (10.2%)
• Common (1% to 10%): Lethargy, convulsion, dizziness postural, syncope
• Rare (less than 0.1%): Hypersomnia
• Postmarketing reports: Tremor, paresthesias, vertigo, taste alteration, hypertensive encephalopathy^[Ref]

Other

• Very common (10% or more): Fatigue (up to 22%)
• Common (1% to 10%): Asthenia
• Uncommon (0.1% to 1%): Chest pain
• Rare (less than 0.1%): Malaise^[Ref]

Metabolic

• Very common (10% or more): Appetite decreased (up to 15%)
• Common (1% to 10%): Weight increased
• Frequency not reported: Body mass index increased
• Postmarketing reports: Edema

Psychiatric

• Common (1% to 10%): Insomnia, depression, anxiety, affect lability, middle insomnia, nightmare, irritability
• Uncommon (0.1% to 1%): Agitation, hallucination
• Postmarketing reports: Confusion^[Ref]

Cardiovascular

• Common (1% to 10%): Hypotension, bradycardia, orthostatic hypotension, tachycardia
• Uncommon (0.1% to 1%): Pallor, atrioventricular block first degree, sinus arrhythmia, blood pressure increased, heart rate decreased
• Rare (less than 0.1%): Hypertension
• Frequency not reported: QTc prolongation
• Postmarketing reports: Palpitations, rebound hypertension

Genitourinary

• Common (1% to 10%): Impotence, enuresis
• Uncommon (0.1% to 1%): Pollakiuria
• Frequency not reported: Urinary frequency increased
• Postmarketing reports: Erectile dysfunction^[Ref]

Dermatologic

• Common (1% to 10%): Rash, pruritus
• Postmarketing reports: Alopecia, dermatitis, exfoliative dermatitis

Respiratory

• Uncommon (0.1% to 1%): Asthma
• Postmarketing reports: Dyspnea

Hepatic

• Uncommon (0.1% to 1%): ALT increased

Immunologic

• Uncommon (0.1% to 1%): Hypersensitivity

Musculoskeletal

• Postmarketing reports: Arthralgia, leg cramps, leg pain, myalgia

Ocular

• Postmarketing reports: Blurred vision

Further information

Guanfacine side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer