Baclofen

# Baclofen ## Overview - **Classification**: Centrally acting skeletal muscle relaxant, antispastic agent. - **Mechanism**: GABAb receptor agonist that inhibits mono- and polysynaptic reflexes at the spinal cord level. Reduces excitatory neurotransmitter release. ## Primary Indications 1. **Spasticity** - Symptomatic relief of spasticity in multiple sclerosis, spinal cord lesions (e.g., trauma, tumor). 2. **Intrathecal Baclofen** - Severe spasticity unresponsive to oral therapy or causing intolerable side effects. 3. **Trigeminal Neuralgia** - Off-label, often as an adjunctive agent. ## Adult Dosing ### Standard Dosing **Spasticity (Oral)** - **Dose**: Start **5 mg** - **Frequency**: **3 times daily (TID)** - **Route**: Oral - **Titration**: Increase by **5 mg TID** every 3 days as needed. - **Maximum Dose**: Oral **80 mg/day** (rarely up to 100 mg/day in some cases). **Severe Spasticity (Intrathecal)** - **Test Dose**: **50 mcg** (administered by physician into subarachnoid space). - **Maintenance**: **300-800 mcg/day** via pump; highly individualized. - **Maximum Dose**: Intrathecal **1000 mcg/day** typically, though some patients require higher doses (up to 2000 mcg/day). ### Dose Adjustments - **Renal Impairment**: Reduce dose significantly. - CrCl < 30 mL/min: Reduce dose by **50% or more**. - ESRD/Dialysis: Use with extreme caution, consider avoiding oral. - **Hepatic Impairment**: No specific dose adjustments; use with caution. - **Elderly Patients**: Start with lower doses (**2.5 mg TID** initially). Slower titration due to increased sensitivity and CNS effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Use**: Generally **not recommended** due to limited data and high risk of CNS/respiratory depression. - **Special Notes**: Reserve for severe cases under specialist supervision only. ### Infants (1-12 months) - **Indication**: Severe spasticity. - **Dose**: Start **0.3 mg/kg/day** - **Frequency**: Divided into **3-4 daily doses** - **Titration**: Increase gradually by **0.2 mg/kg/day** every 3 days. - **Maximum**: **1 mg/kg/day** (rarely up to 2 mg/kg/day in complex cases). - **Special Notes**: Closely monitor for sedation, respiratory depression, and hypotonia. ### Children (1-12 years) - **Indication**: Spasticity. - **Dose**: Start **0.3 mg/kg/day** or **5 mg** - **Frequency**: Divided into **3-4 daily doses** - **Titration**: Increase gradually every 3 days as needed: - Age 2-7 years: Increase by **2.5-5 mg/day**. - Age 8-12 years: Increase by **5-10 mg/day**. - **Maximum**: - Under 8 years: Oral **40 mg/day**. - 8-12 years: Oral **60 mg/day** (some guidelines permit up to 80 mg/day for severe cases). ### Adolescents (13-18 years) - **Dose**: Follow **adult oral dosing** guidelines. - **Frequency**: Start **5 mg TID**. - **Titration**: Increase by **5 mg TID** every 3 days. - **Maximum**: Oral **80 mg/day**. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to baclofen. - **Absolute**: Intrathecal formulation for IV, SC, IM administration. - **Relative**: Epilepsy (may lower seizure threshold). ### Common Adverse Effects - **Very Common (>10%)**: Drowsiness, dizziness, weakness, nausea, headache. - **Common (1-10%)**: Confusion, insomnia, ataxia, hypotension, urinary frequency, constipation. - **Serious but Rare**: Seizures (especially with abrupt withdrawal), hallucinations, respiratory depression, rhabdomyolysis. ### Key Drug Interactions - **CNS Depressants (alcohol, opioids, benzodiazepines)**: Enhanced sedation and respiratory depression. Avoid concurrent use or dose reduction required. - **Antihypertensives**: Increased risk of hypotension. Monitor blood pressure closely. - **Tricyclic Antidepressants (TCAs)**: Potentiates muscle relaxant effects. Monitor for increased sedation. ## Monitoring & Follow-up - **Before Treatment**: Baseline renal function (BUN/Cr). - **During Treatment**: Assess spasticity improvement and adverse effects (e.g., sedation). Monitor vital signs (BP, HR). - **Clinical Signs**: Watch for signs of overdose (profound sedation, coma, respiratory depression) or withdrawal (seizures, hallucinations, rebound spasticity). ## Clinical Pearls - 💡 **Titration is key**: Start low and increase dose slowly to minimize side effects. - 💡 **Do not abruptly stop**: Taper dose over 1-2 weeks to prevent severe withdrawal symptoms. - 💡 **Food administration**: Take with food or milk to minimize GI upset. - 💡 **Impaired driving**: Advise patients against driving or operating machinery until effects are known. - 💡 **Intrathecal risks**: Intrathecal pump failure or abrupt discontinuation can be life-threatening. Seek immediate medical attention if symptoms occur. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.