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# Lennox-Gastaut Syndrome (LGS)
## Overview
Lennox-Gastaut Syndrome is a severe form of childhood-onset epilepsy characterized by multiple seizure types (tonic, atonic, absence), slow spike-wave patterns on EEG, and intellectual impairment. Management is palliative and typically requires polytherapy.
## Primary Indications
Adjunctive therapy for seizures associated with Lennox-Gastaut Syndrome. Approved agents include Clobazam, Rufinamide, Topiramate, Felbamate, Cannabidiol, and Fenfluramine.
## Adult Dosing
* **Clobazam:** Start 5–10 mg/day, titrated to 20 mg/day.
* **Rufinamide:** Start 400–800 mg/day; titrate upward to 3,200 mg/day in divided doses.
* **Cannabidiol:** 10–20 mg/kg/day in two divided doses.
* **Topiramate:** Titrate to 200–400 mg/day in two divided doses.
* **Felbamate:** 1,200–3,600 mg/day in three to four divided doses.
## Pediatric Dosing
* **Clobazam (≥2 years):** Weight-based: <30 kg, start 5 mg/day, target 20 mg/day; ≥30 kg, start 10 mg/day, target 40 mg/day.
* **Rufinamide (≥1 year):** Start ~10 mg/kg/day; titrate to 45 mg/kg/day (max 3,200 mg/day).
* **Cannabidiol (≥1 year):** 10–20 mg/kg/day (divided BID).
* **Fenfluramine (≥2 years):** Start 0.2 mg/kg BID; titrate to 0.35 mg/kg BID (max 26 mg/day).
* **Topiramate (≥2 years):** Titrate to 5–9 mg/kg/day (daily max typically 400 mg).
## Dose Adjustments
* **Hepatic Impairment:** Significant dose reductions required for Clobazam; Felbamate should generally be avoided.
* **Renal Impairment:** Reduce starting dose and titration rate for Rufinamide (CrCl <30 mL/min); Topiramate requires 50% dose reduction in severe renal impairment.
## Contraindications
* **Felbamate:** History of hepatic failure or blood dyscrasias.
* **Rufinamide:** Familial Short QT syndrome.
* **Clobazam:** History of hypersensitivity to benzodiazepines.
## Adverse Effects
* **Common:** Somnolence, fatigue, dizziness, gastrointestinal distress, ataxia.
* **Serious:**
* *Felbamate:* Aplastic anemia, acute liver failure.
* *Topiramate:* Metabolic acidosis (hyperchloremic), nephrolithiasis, cognitive slowing.
* *Cannabidiol:* Elevated transaminases.
* *Fenfluramine:* Valvulopathy and pulmonary hypertension (requires periodic echocardiogram).
## Key Drug Interactions
* **Clobazam:** Potent CYP2C19 inhibitor; increases levels of active metabolite of phenytoin; benzodiazepine synergism with CNS depressants.
* **Topiramate:** May decrease efficacy of oral contraceptives.
* **Cannabidiol:** Increases serum levels of clobazam's active metabolite (N-desmethylclobazam); monitor for increased sedation.
* **Valproate:** Increases levels of rufinamide and topiramate; requires dose titration monitoring.
## Monitoring
* **Baseline/Routine:** Liver function tests (LFTs) for Cannabidiol and Felbamate.
* **Cardiac:** EKG for Rufinamide; echocardiograms for Fenfluramine.
* **Hematology:** CBC monitoring for Felbamate.
* **Chemistry:** Serum bicarbonate for Topiramate.
## Clinical Pearls
* LGS is notoriously refractory to monotherapy; polypharmacy is standard practice.
* *Felbamate* is highly effective but reserved for refractory cases due to black box warnings for aplastic anemia and hepatotoxicity.
* *Clobazam* tolerance may develop over time, requiring dose adjustments.
* When initiating *Cannabidiol* in patients on *Clobazam*, anticipate the need to reduce the clobazam dose due to increased exposure to the active metabolite.
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**Educational Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Dosing protocols may vary by institution and patient-specific factors. Always consult the latest package inserts and institutional clinical guidelines before prescribing or dispensing medications.
