LIORESAL
Clinical safety rating
cautionComprehensive clinical and safety monograph for LIORESAL (LIORESAL).
GABA-B receptor agonist; inhibits monosynaptic and polysynaptic reflexes at the spinal cord level by reducing excitatory neurotransmitter release.
| Metabolism | Hepatic metabolism via deamination (minor pathway); primarily excreted unchanged in urine (70-80% as parent drug, 15% as metabolites). |
| Excretion | Renal: approximately 70-80% of the dose as unchanged drug and metabolites (primarily glucuronide conjugate); minor biliary/fecal elimination (<5%). |
| Half-life | Terminal elimination half-life: 2.5-4 hours. Clinically, accumulation occurs in renal impairment, requiring dose adjustment. |
| Protein binding | ~30%; primarily bound to albumin. |
| Volume of Distribution | 0.5-1.0 L/kg; indicates moderate tissue distribution, with higher CNS penetration when administered intrathecally. |
| Bioavailability | Oral: 70-80% (first-pass effect minimal); intrathecal: nearly 100% due to direct CSF administration. |
| Onset of Action | Oral: 30-60 minutes to peak effect; intrathecal: 0.5-1 hour for spasticity reduction. |
| Duration of Action | Oral: 4-8 hours; intrathecal: 8-12 hours with continuous infusion or bolus. Note: duration may be shorter in patients with high spasticity tolerance. |
| Molecular Weight | 213.66 |
| Action Class | Skeletal muscle relaxant- Centrally acting |
Oral: Initial 5 mg 3 times daily, increase by 5 mg per dose every 3 days to a maximum of 80 mg/day (20 mg 4 times daily). Intrathecal: Test dose 50-100 mcg; maintenance infusion 300-800 mcg/day.
| Dosage form | INJECTABLE |
| Renal impairment | GFR >60 mL/min: no adjustment; GFR 30-60: reduce dose by 25-50%; GFR <30: avoid or reduce by 75%; hemodialysis: supplement dose after dialysis. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | Oral: 2.5 mg 4 times daily initially, increase by 2.5-5 mg every 3 days to max 40 mg/day (2-7 years) or 60 mg/day (8-15 years). Intrathecal: test dose 25-50 mcg; maintenance 100-1000 mcg/day. |
| Geriatric use | Start at 5 mg twice daily; increase slowly due to increased CNS sensitivity; monitor for sedation and confusion. |
| 1st trimester | Limited human data; animal studies show adverse effects. Use only if potential benefit outweighs risk. |
| 2nd trimester | May cause fetal abnormalities; avoid unless essential. |
| 3rd trimester | Risk of neonatal withdrawal (irritability, seizures) if used near term; consider tapering. |
Clinical note
Comprehensive clinical and safety monograph for LIORESAL (LIORESAL).
| Placental transfer | Crosses placenta detectable in amniotic fluid and fetal plasma; animal studies show skeletal anomalies. |
| Breastfeeding | Enters breast milk in low concentrations; monitor infant for drowsiness, hypotonia. Caution with preterm neonates or impaired renal function. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Increased risk of orofacial clefts (cleft palate) based on animal studies and limited human data. Second and third trimesters: Risk of fetal bradycardia, hypotonia, and withdrawal symptoms (irritability, tremors) in neonates. Use only if benefit outweighs risk. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of central nervous system depression. Fetal monitoring should include heart rate and growth parameters. Neonatal monitoring for withdrawal symptoms (hypertonia, seizures) for 48-72 hours postpartum. |
| Fertility Effects | No significant adverse effects on fertility reported in human studies. Animal studies showed no impairment of fertility. Baclofen may cause reversible ejaculatory dysfunction in males. |
■ FDA Black Box Warning
Abrupt discontinuation of intrathecal baclofen may result in life-threatening withdrawal reactions (high fever, altered mental status, severe spasticity, rhabdomyolysis, autonomic dysfunction).
| Serious Effects |
Hypersensitivity to baclofenSevere psychiatric disorders (relative)
| Precautions | Abrupt discontinuation: may cause withdrawal symptoms (hallucinations, seizures, hyperthermia, rebound spasticity). Sedation: may impair ability to drive or operate machinery. Renal impairment: dose adjustment required. Avoid concomitant use with CNS depressants (alcohol, benzodiazepines). Caution in stroke patients, respiratory depression, psychiatric disorders, epilepsy, and pregnancy. |
| Food/Dietary | No specific food interactions, but take with or without food consistently to avoid variable absorption. |
| Clinical Pearls | Titrate slowly to avoid sedation and muscle weakness; monitor for withdrawal signs after abrupt discontinuation (e.g., spasticity rebound, hyperpyrexia, seizures). Intrathecal pump requires specialist management. |
| Patient Advice | Take exactly as prescribed; do not suddenly stop taking this medication. · Avoid alcohol and other CNS depressants. · May cause drowsiness or dizziness; avoid driving until you know how it affects you. · Report any unusual muscle weakness, confusion, or difficulty breathing. · Keep medication in original container away from moisture and heat. |
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