Muscle Relaxant — GABA-B Agonist
Pregnancy: Avoid in first trimester; use only if clearly needed
Baclofen
Brand names: Lioresal
Adult dose
Dose: 5 mg three times daily initially, increasing to 30-75 mg/day
Route: Oral
Frequency: Three times daily
Max: 100 mg/day (under specialist supervision)
Intrathecal baclofen pump used for severe spasticity refractory to oral treatment
Paediatric dose
Dose: 0.3 mg/kg/day initially, increasing to 0.75-2 mg/kg/day mg/day/kg
Route: Oral
Frequency: Three to four times daily
Max: 40 mg/day (under 8 years); 60 mg/day (8-18 years)
Child 1 month to 1 year: 0.5-1 mg/kg/day in divided doses. Child 1-10 years: 0.75-2 mg/kg/day (max 40 mg/day). Child 10 years and over: up to 2.5 mg/kg/day (max 60 mg/day). Increase dose gradually over weeks — abrupt withdrawal causes seizures and hallucinations
Dose adjustments
Renal
Significant reduction required — renally excreted; start at very low doses
Hepatic
Use with caution
Paediatric weight-based calculator
Child 1 month to 1 year: 0.5-1 mg/kg/day in divided doses. Child 1-10 years: 0.75-2 mg/kg/day (max 40 mg/day). Child 10 years and over: up to 2.5 mg/kg/day (max 60 mg/day). Increase dose gradually over weeks — abrupt withdrawal causes seizures and hallucinations
Clinical pearls
- Abrupt withdrawal is dangerous — can cause hyperthermia, hallucinations, seizures, and autonomic instability (especially with intrathecal pump); always taper slowly
- Primary indication in paediatrics: spasticity in cerebral palsy, spinal cord injury, and multiple sclerosis in adolescents
- Intrathecal baclofen pump delivers drug directly to CSF — allows much lower doses with fewer systemic side effects; used for severe spasticity refractory to oral therapy
- Overdose features: CNS depression, coma, respiratory depression, hypotonia, seizures; treat supportively
- GABA-B receptor agonist — reduces excitatory neurotransmitter release at spinal level
Contraindications
- Peptic ulcer disease
- Epilepsy (lowers seizure threshold at high doses)
Side effects
- Sedation
- Muscle weakness
- Hypotonia
- Dizziness
- Nausea
- Urinary retention
- Constipation
- Seizures (overdose or abrupt withdrawal)
Interactions
- CNS depressants (additive sedation)
- Antihypertensives (enhanced hypotensive effect)
- Tricyclic antidepressants (additive muscle relaxation)
Monitoring
- Muscle tone and spasticity scores
- Motor function
- Sedation level
- Signs of withdrawal if dose missed
Reference: BNF for Children; NICE NG62 (Spasticity in under 19s); Royal College of Physicians Spasticity Guideline. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.