What is the recommended dosage of riluzole (Rilutek) for motor neuron disease, specifically amyotrophic lateral sclerosis (ALS)?

Recommended Dosage of Riluzole for Motor Neuron Disease (ALS)

The recommended dosage of riluzole for amyotrophic lateral sclerosis (ALS) is 50 mg taken orally twice daily, at least 1 hour before or 2 hours after a meal. 1

Dosing Regimen Details

• Riluzole is administered as a 50 mg oral tablet twice daily (total daily dose of 100 mg) 1
• Timing of administration is important: take at least 1 hour before or 2 hours after meals to ensure optimal absorption 1
• The 100 mg daily dose has been established as the optimal therapeutic dose based on clinical trials showing efficacy in prolonging survival 2, 3
• Dosage should not be increased beyond 100 mg daily, as higher doses (200 mg) did not show significantly better outcomes but increased adverse effects 2

Monitoring Requirements

• Serum aminotransferases (liver enzymes) should be measured before starting treatment and regularly during therapy 1
• Monthly monitoring of liver function is recommended for the first 3 months of treatment, then periodically thereafter 1
• Complete blood count should be monitored, particularly in the first few months, due to risk of neutropenia 1
• Discontinue riluzole if:
  • Hepatic transaminases exceed 5 times the upper limit of normal 1
  • Evidence of liver dysfunction develops (e.g., elevated bilirubin) 1
  • Interstitial lung disease develops 1

Clinical Efficacy

• Riluzole extends tracheostomy-free survival by approximately 2-3 months (median survival increased from 11.8 to 14.8 months) 3
• The drug provides a 9% increase in probability of surviving one year (from 49% with placebo to 58% with riluzole) 3
• Riluzole has shown a small beneficial effect on both bulbar and limb function, though not on muscle strength 3

Common Adverse Effects

• Most frequent adverse events include:
  • Asthenia (weakness)
  • Nausea
  • Dizziness
  • Decreased lung function
  • Abdominal pain
  • Elevated liver enzymes 1
• Threefold increase in serum alanine transferase is more frequent in riluzole-treated patients than controls 3

Special Considerations

• CYP1A2 activity significantly correlates with riluzole clearance, accounting for approximately 37% of the observed variability in drug metabolism 4
• Avoid concomitant use with strong to moderate CYP1A2 inhibitors as this may increase riluzole-associated adverse reactions 1
• Avoid concomitant use with strong to moderate CYP1A2 inducers as this may decrease efficacy 1
• Use caution when combining riluzole with other hepatotoxic drugs, as this may increase risk of hepatotoxicity 1
• Nutritional status is an important prognostic factor in ALS patients, and weight loss during riluzole treatment should be monitored 5

Clinical Pearls

• Early initiation of riluzole therapy may provide greater benefit 6
• Patient education about realistic expectations is important, as the modest efficacy may lead to disenchantment and discontinuation 6
• Despite its modest efficacy, riluzole remains the only FDA-approved medication shown to prolong survival in ALS patients 1, 3