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GABA-B Agonist Muscle Relaxant Pregnancy: Use only if benefit outweighs risk — animal data shows teratogenicity at high doses; consult specialist

Baclofen

Brand names: Lioresal

Adult dose

Dose: 5 mg three times daily increasing by 5 mg every 3 days; usual effective dose 30–75 mg/day
Route: Oral
Frequency: Three times daily
Max: 100 mg/day under hospital supervision; typically 75 mg/day in practice
Titrate slowly to minimise sedation; never stop abruptly — serious withdrawal risk; taper over 1–4 weeks

Paediatric dose

Dose: 0.3–0.5 initially increasing to maintenance 0.75–2 mg/day/kg
Route: Oral
Frequency: Three to four times daily
Max: 40 mg/day (2–10 years); 60 mg/day (>10 years)
Intrathecal baclofen pump for severe cerebral palsy spasticity — specialist use only

Dose adjustments

Renal

Significant dose reduction required in renal impairment — baclofen is renally eliminated; toxicity risk in CKD

Hepatic

No significant adjustment required

Paediatric weight-based calculator

Intrathecal baclofen pump for severe cerebral palsy spasticity — specialist use only

Clinical pearls

  • Mechanism: GABA-B receptor agonist at spinal cord level — inhibits mono- and polysynaptic reflexes; particularly effective for spinal spasticity (spinal cord injury, MS) but less effective for cerebral spasticity (stroke, TBI)
  • Orthopaedic spasm: useful for acute lumbar disc herniation with significant muscle spasm, cervical myelopathy spasticity, and post-spinal surgery pain — short courses of 7–14 days adjunct to analgesia and physiotherapy
  • Critical withdrawal warning: abrupt cessation causes hallucinations, seizures, rebound spasticity, hyperthermia, and rhabdomyolysis — one of the most dangerous withdrawal syndromes among muscle relaxants; always taper over 1–4 weeks
  • Intrathecal baclofen (ITB pump): pump failure or catheter disconnection causes acute life-threatening withdrawal — orthopaedic and anaesthetic teams must identify ITB patients from history before any surgical procedure; emergency ITB withdrawal protocol required
  • STOPP criteria in elderly: significant risk of confusion, falls, and paradoxical hallucinations — start at 5 mg once or twice daily; prefer physiotherapy and shorter courses in older patients

Contraindications

  • Peptic ulcer disease (relative)
  • Psychotic disorders (relative)
  • Epilepsy (may lower seizure threshold — use with caution)

Side effects

  • Sedation
  • Weakness
  • Hypotonia
  • Nausea
  • Dizziness
  • Confusion in elderly
  • Hallucinations
  • Seizures on abrupt withdrawal

Interactions

  • Antihypertensives — additive hypotension
  • Tricyclics — increased sedation and hypotonia
  • Alcohol — enhanced CNS depression
  • Lithium — hyperkinesia and worsening spasticity reported
  • MAOIs — avoid combination

Monitoring

  • Spasticity scale (Modified Ashworth Scale)
  • Functional mobility
  • Sedation level
  • Renal function in CKD
  • Signs of withdrawal on dose reduction

Reference: BNFc; BNF 90; NICE NG159 (Spasticity in Adults); SPC Lioresal; Cochrane Review (Baclofen for Spasticity); SIGN 113. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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