Baclofen Side Effects
Baclofen commonly causes transient drowsiness (10-63%), dizziness (5-15%), weakness (5-15%), and fatigue (2-4%) as its primary side effects. 1 These side effects are typically dose-related, transient, and reversible, but can significantly impact patient functioning.
Common Side Effects
Neuropsychiatric Effects
- Drowsiness/sedation (10-63%)
- Dizziness (5-15%)
- Weakness (5-15%)
- Fatigue (2-4%)
- Confusion (1-11%)
- Headache (4-8%)
- Insomnia (2-7%)
Gastrointestinal Effects
- Nausea (4-12%)
- Constipation (2-6%)
- Rarely: dry mouth, anorexia, taste disorders, abdominal pain, vomiting, diarrhea
Cardiovascular Effects
- Hypotension (0-9%)
- Rarely: dyspnea, palpitations, chest pain, syncope
Genitourinary Effects
- Urinary frequency (2-6%)
- Rarely: urinary retention, dysuria, sexual dysfunction
Severe Adverse Effects and Special Considerations
Withdrawal Syndrome
Abrupt discontinuation of baclofen can lead to potentially life-threatening withdrawal symptoms, especially after long-term use:
- Visual and auditory hallucinations
- Anxiety and agitation
- Delirium and confusion
- Fever and hyperthermia
- Tremors and seizures
- Tachycardia
- Rebound spasticity and muscle rigidity
Withdrawal from intrathecal baclofen is particularly dangerous and can lead to rhabdomyolysis, multiorgan failure, and death 2. Baclofen should always be tapered slowly when discontinuing.
Special Populations
- Elderly patients: More susceptible to adverse effects including sedation, confusion, and falls. A recent systematic review found concerning adverse effects in adults over 50 years, with 27.8% incidence of falls reported 3.
- Renal impairment: Higher risk of toxicity due to reduced clearance, potentially leading to encephalopathy 3.
- Combination with CNS depressants: Increased risk of sedation and respiratory depression when combined with other CNS depressants.
Clinical Pearls
Start low, go slow: Begin with low doses and titrate gradually, especially in elderly patients or those with renal impairment.
Monitor for side effects: Regular assessment for drowsiness, confusion, weakness, and hypotension is essential.
Avoid abrupt discontinuation: Always taper baclofen slowly to prevent potentially life-threatening withdrawal syndrome.
Use caution with concomitant medications: Be particularly careful when combining with other CNS depressants or medications that can cause hypotension.
Patient education: Inform patients about potential side effects, especially drowsiness that may affect driving and operating machinery.
Baclofen remains an important medication for spasticity management and other indications, but careful monitoring and patient education are essential to minimize adverse effects and ensure safe use.