Baclofen Adverse Effects
Baclofen commonly causes central nervous system effects and muscle-relaxation–related symptoms. (dailymed.nlm.nih.gov) Clinically important risks include abrupt discontinuation (particularly for intrathecal therapy) and medication withdrawal-related neuropsychiatric and neurologic toxicity. (dailymed.nlm.nih.gov)
Commonly Reported Adverse Reactions (Oral Baclofen)
Transient drowsiness is reported in 63% of patients receiving baclofen versus 36% receiving placebo in one controlled study of 175 patients. (dailymed.nlm.nih.gov) Dizziness is reported in 5% to 15% of patients. (dailymed.nlm.nih.gov) Weakness is reported in 5% to 15% of patients. (dailymed.nlm.nih.gov) Fatigue is reported in 2% to 4% of patients. (dailymed.nlm.nih.gov)
Central Nervous System and Neuropsychiatric Effects
Confusion is reported in 1% to 11% of patients. (dailymed.nlm.nih.gov) Headache is reported in 4% to 8% of patients. (dailymed.nlm.nih.gov) Insomnia is reported in 2% to 7% of patients. (dailymed.nlm.nih.gov) Hallucinations, euphoria, excitation, depression, and other neurologic symptoms are reported rarely. (dailymed.nlm.nih.gov)
Gastrointestinal and Other Common Effects (Oral Baclofen)
Nausea is reported in 4% to 12% of patients. (dailymed.nlm.nih.gov) Constipation is reported in 2% to 6% of patients. (dailymed.nlm.nih.gov) Dry mouth, anorexia, taste disorder, abdominal pain, vomiting, and diarrhea are reported rarely. (dailymed.nlm.nih.gov)
Genitourinary Effects (Oral Baclofen)
Urinary findings are possible and some genitourinary symptoms may be attributable to the underlying disease rather than to baclofen therapy. (dailymed.nlm.nih.gov)
Abrupt Withdrawal and Discontinuation Risks (Oral and Intrathecal Baclofen)
Hallucinations and seizures have been reported on abrupt withdrawal of baclofen. (dailymed.nlm.nih.gov) Dose reduction should be gradual when discontinuing baclofen because of risks associated with abrupt withdrawal. (dailymed.nlm.nih.gov) Intrathecal baclofen has a boxed warning against abrupt discontinuation because reported sequelae include high fever, altered mental status, exaggerated rebound spasticity, and muscle rigidity, which can progress in rare cases to rhabdomyolysis, multiple organ-system failure, and death. (dailymed.nlm.nih.gov) Seizures have been reported with overdose and with withdrawal from baclofen injection (intrathecal) as well as in patients maintained on therapeutic doses of intrathecal baclofen. (dailymed.nlm.nih.gov)
Overdose-Related Toxicity (Oral and Intrathecal Baclofen)
Overdose may cause vomiting, muscular hypotonia, drowsiness, accommodation disorders, coma, respiratory depression, and seizures. (dailymed.nlm.nih.gov)
Adverse Events During Intrathecal Pump Therapy (Intrathecal Baclofen)
Intrathecal baclofen therapy can present with decreased therapeutic response that can reflect withdrawal or pump/catheter-related issues. (dailymed.nlm.nih.gov) During pump-related problems, early manifestations can include worsening spasticity, return of spasticity, withdrawal symptoms, poor response to escalating doses, or frequent or large dosage increases. (dailymed.nlm.nih.gov)