Baclofen Side Effects

In Summary

Commonly reported side effects of baclofen include: drowsiness. Other side effects include: asthenia, dizziness, headache, and nausea. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to baclofen: oral powder for suspension, oral tablet

In addition to its needed effects, some unwanted effects may be caused by baclofen. In the event that any of these side effects do occur, they may require medical attention.

Severity: Moderate

If any of the following side effects occur while taking baclofen, check with your doctor or nurse as soon as possible:

Less common or rare:

• Bloody or dark urine
• chest pain
• fainting
• hallucinations (seeing or hearing things that are not there)
• mental depression or other mood changes
• ringing or buzzing in the ears
• skin rash or itching

Symptoms of overdose:

• Blurred or double vision
• convulsions (seizures)
• muscle weakness (severe)
• shortness of breath or unusually slow or troubled breathing
• vomiting

Minor Side Effects

Some of the side effects that can occur with baclofen may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:

• Confusion
• dizziness or lightheadedness
• drowsiness
• nausea
• unusual weakness, especially muscle weakness

Less common or rare:

• Abdominal or stomach pain or discomfort
• clumsiness, unsteadiness, trembling, or other problems with muscle control
• constipation
• diarrhea
• difficult or painful urination or decrease in amount of urine
• false sense of well-being
• frequent urge to urinate or uncontrolled urination
• headache
• loss of appetite
• low blood pressure
• muscle or joint pain
• numbness or tingling in hands or feet
• pounding heartbeat
• sexual problems in males
• slurred speech or other speech problems
• stuffy nose
• swelling of ankles
• trouble in sleeping
• unexplained muscle stiffness
• unusual excitement
• unusual tiredness
• weight gain

Side Effects: Post Treatment

After you stop taking this drug, it is possible that you may still experience side effects that need medical attention. If you notice any of the following side effects check with your doctor immediately:

• Convulsions (seizures)
• hallucinations (seeing or hearing things that are not there)
• increase in muscle spasm, cramping, or tightness
• mood or mental changes
• unusual nervousness or restlessness

Applies to baclofen: intrathecal kit, intrathecal solution

In addition to its needed effects, some unwanted effects may be caused by baclofen. In the event that any of these side effects do occur, they may require medical attention.

Severity: Moderate

If any of the following side effects occur while taking baclofen, check with your doctor or nurse as soon as possible:

More common:

• Convulsions (seizures)

Less common or rare:

• Blurred vision or double vision
• fainting
• mental depression
• muscle weakness
• ringing or buzzing in ears
• seeing, hearing, or feeling things that are not there
• shortness of breath or troubled breathing

Symptoms of overdose:

• Convulsions (seizures)
• dizziness, drowsiness, or lightheadedness
• increased watering of the mouth
• mental confusion
• muscle weakness
• nausea and/or vomiting
• shortness of breath or troubled breathing

Minor Side Effects

Some of the side effects that can occur with baclofen may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:

• Constipation
• difficult urination
• dizziness
• headache
• nausea and/or vomiting
• numbness or tingling in hands or feet
• sleepiness

Less common:

• Clumsiness, unsteadiness, trembling, or other problems with muscle control
• diarrhea
• difficulty sleeping
• dizziness or lightheadedness, especially when getting up from a lying or sitting position
• dry mouth
• frequent urge to urinate
• irritation of the skin at the site where the pump is located
• itching of the skin
• sexual problems
• slurred speech or other speech problems
• swelling of ankles, feet, or lower legs
• trembling or shaking

Side Effects: Post Treatment

After you stop taking this drug, it is possible that you may still experience side effects that need medical attention. If you notice any of the following side effects check with your doctor immediately:

• Convulsions (seizures)
• facial flushing, headache, increased sweating, or slow heartbeat
• increased muscle spasms
• seeing, hearing, or feeling things that are not there

For Healthcare Professionals

Applies to baclofen: compounding powder, intrathecal solution, oral suspension, oral tablet

Cardiovascular

Common (1% to 10%): Cardiac output decreased, hypotension, hypertension, diminished cardiovascular functions, peripheral edema
Rare (less than 0.1%): Arrhythmias, palpitations, chest pain
Frequency not reported: Bradycardia, orthostatic hypotension^[Ref]

Dermatologic

Common (1% to 10%): Rash, hyperhidrosis, urticaria/pruritus, facial edema
Uncommon (0.1% to 1%): Alopecia, diaphoresis
Frequency not reported: Rash, sweating, contact dermatitis, skin ulcer^[Ref]

Endocrine

Common (1% to 10%): Ovarian cysts are palpable in 4% of women treated with for up to one year^[Ref]

Gastrointestinal

Very common (10% or more): Nausea (especially at start of therapy) (up to 11%)
Common (1% to 10%): Dry mouth, GI disorder/disturbance, constipation, diarrhea, retching, vomiting, increased salivation
Uncommon (0.1% to 1%): Dysphagia, dehydration, ileus, decreased taste sensation
Rare (less than 0.1%): Colicky abdominal pain, anorexia
Frequency not reported: GI hemorrhage^[Ref]

Genitourinary

Very common (10% or more): Urinary retention (up to 12%)
Common (1% to 10%): Urinary incontinence, urination impaired, sexual dysfunction, urinary frequency, enuresis, dysuria
Rare (less than 0.1%): Erectile dysfunction
Frequency not reported: Dysuria, abnormal ejaculation, oliguria, vaginitis^[Ref]

Hematologic

Frequency not reported: Leukocytosis, petechial rash^[Ref]

Hepatic

Rare (less than 0.1%): Disorders of hepatic function (e.g., increased AST)^[Ref]

Immunologic

Common (1% to 10%): Pneumonia
Uncommon (0.1% to 1%): Septicemia^[Ref]

Metabolic

Common (1% to 10%): Decreased appetite
Frequency not reported: Blood glucose increased^[Ref]

Musculoskeletal

Very common (10% or more): Hypotonia (up to 52%), lower extremity weakness (up to 15%), disturbances of gait and balance
Common (1% to 10%): Muscular weakness, myalgia, upper extremity weakness, back pain, muscular hypertonia^[Ref]

Nervous system

Very common (10% or more): Somnolence (up to 28%), drowsiness (up to 18%), headache (up to 16%), seizures (especially on discontinuation of therapy) (up to 15%), sedation, dizziness (up to 12%)
Common (1% to 10%): Fatigue, ataxia, tremor, lightheadedness, lassitude, exhaustion, numbness/itching/tingling, slurred speech, lethargy, hypertonia, paresthesia
Rare (less than 0.1%): Dysarthria, dysgeusia, syncope, dyskinesia, coma, potentially life-threatening withdrawal symptoms (as a result of sudden interruption of drug delivery)^[Ref]

Other

Common (1% to 10%): Tinnitus, pain, asthenia
Uncommon (0.1% to 1%): Accidental injury, weight loss
Very rare (less than 0.01%): Hypothermia
Frequency not reported: Drug withdrawal syndrome
Uncommon (0.1% to 1%): Subdural hemorrhage, accidental injury, weight loss^[Ref]

Ocular

Common (1% to 10%): Nystagmus, visual impairment, accommodation disorder, blurred vision, double vision, amblyopia^[Ref]

Psychiatric

Common (1% to 10%): Confusional state, hallucination, depression, insomnia, euphoric mood, nightmare, personality changes
Uncommon (0.1% to 1%): Memory loss/impairment, suicidal ideation, attempted suicide
Rare (less than 0.1%): Excitement^[Ref]

Renal

Very rare (less than 0.01%): Kidney calculus^[Ref]

Respiratory

Common (1% to 10%): Respiratory depression, hypoventilation, dyspnea, bradypnea, feeling of pressure in the chest^[Ref]

Not all side effects for baclofen may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.