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.

Applies to baclofen: oral powder for suspension, oral tablet

Other dosage forms:

• intrathecal solution

Along with its needed effects, baclofen 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 as soon as possible if any of the following side effects occur while taking baclofen:

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

Some side effects of baclofen 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

• 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

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:

• 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: compounding powder, intrathecal solution, oral suspension, oral tablet

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

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

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

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

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

Frequency not reported: Leukocytosis, petechial rash

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

Common (1% to 10%): Pneumonia

Uncommon (0.1% to 1%): Septicemia

Common (1% to 10%): Decreased appetite

Frequency not reported: Blood glucose increased

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

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)

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

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

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

Very rare (less than 0.01%): Kidney calculus

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