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Muscle Relaxant — GABA-B Agonist Pregnancy: Use with caution — neonatal withdrawal possible; avoid abrupt discontinuation

Baclofen

Brand names: Lioresal

Adult dose

Dose: 5 mg three times daily initially; increase by 5 mg every 3 days; usual maintenance 30–75 mg/day
Route: Oral / Intrathecal (pump)
Frequency: Three times daily
Max: 100 mg/day (oral); intrathecal dose titrated individually
First-line oral antispastic agent for spasticity in MS, spinal cord injury, and stroke. GABA-B agonist — inhibits monosynaptic and polysynaptic spinal reflex arcs. Intrathecal baclofen pump for refractory severe spasticity. Abrupt withdrawal causes life-threatening baclofen withdrawal syndrome.

Paediatric dose

Dose: 0.3 mg/day/kg
Route: Oral
Frequency: Three times daily
Max: 2 mg/kg/day (max 60 mg/day)
Children ≥12 months: 0.3 mg/kg/day in 3 divided doses; increase slowly. Max 2 mg/kg/day.

Dose adjustments

Renal

Significant dose reduction in renal impairment — renally excreted. Start at 5 mg once daily and titrate slowly; accumulation causes toxicity.

Hepatic

No specific adjustment.

Paediatric weight-based calculator

Children ≥12 months: 0.3 mg/kg/day in 3 divided doses; increase slowly. Max 2 mg/kg/day.

Clinical pearls

  • Baclofen withdrawal syndrome: LIFE-THREATENING — seizures, hyperthermia, rhabdomyolysis, multiorgan failure. Never stop abruptly — taper over minimum 1–2 weeks. If missed doses due to pump failure: emergency dose escalation.
  • Intrathecal baclofen pump: surgical implant for refractory spasticity — delivers drug directly to CSF; 100–1000× more potent than oral. Pump failure = medical emergency.
  • Renal dosing is critical — accumulation in kidney disease causes severe toxicity (confusion, coma, respiratory depression)

Contraindications

  • Peptic ulcer (active — use with caution)
  • Epilepsy (lowers seizure threshold — use with caution)

Side effects

  • Sedation and drowsiness
  • Muscle weakness
  • Hypotension
  • Nausea
  • Urinary frequency
  • Confusion (especially elderly)

Interactions

  • CNS depressants (additive sedation)
  • Antihypertensives (additive hypotension)
  • Tricyclic antidepressants (additive muscle hypotonia)
  • Lithium (additive CNS effects)

Monitoring

  • Spasticity scales (Modified Ashworth Scale)
  • Renal function (dose titration)
  • Sedation
  • Blood pressure

Reference: BNFc; BNF 90; NICE NG109 (Spasticity in adults); BNFc; UK Baclofen Pump Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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