1. Clinical Overview
Riluzole is a benzothiazole derivative and the first disease-modifying agent approved for the treatment of Amyotrophic Lateral Sclerosis (ALS). It is a neuroprotective agent that modulates glutamatergic neurotransmission. In the Indian context, it is a critical but high-cost therapy for a debilitating neurological condition, often requiring patient assistance programs for access.
| Onset | Duration | Bioavailability |
|---|---|---|
| Pharmacological effects begin within hours, but clinical benefit in slowing ALS progression may take weeks to months to become evident. | Approximately 12 hours, supporting a twice-daily dosing regimen. | Approximately 60% (oral). Absorption is reduced by a high-fat meal. |
2. Mechanism of Action
Riluzole's primary mechanism is the inhibition of glutamate release from pre-synaptic terminals. It also inactivates voltage-dependent sodium channels on neurons, preventing sustained neuronal firing. Furthermore, it non-competitively blocks NMDA and kainate subtypes of glutamate receptors. This multi-pronged approach reduces excitotoxic neuronal damage, a key pathological process in ALS.
3. Indications & Uses
- Amyotrophic Lateral Sclerosis (ALS) - to prolong survival and delay the need for tracheostomy
4. Dosage & Administration
Adult Dosage: 50 mg every 12 hours (on an empty stomach, at least 1 hour before or 2 hours after meals).
Administration: Take tablet whole with a glass of water. Must be taken at least 1 hour before or 2 hours after meals to ensure consistent absorption. Maintain a consistent dosing schedule.
5. Side Effects
Common side effects may include:
- Asthenia (weakness, fatigue)
- Nausea
- Dizziness
- Diarrhea
- Abdominal pain
- Elevated liver enzymes (ALT/AST)
- Headache
- Decreased lung function
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Ciprofloxacin | Potent CYP1A2 inhibitor; increases riluzole plasma levels by up to 120%. Risk of toxicity. | Major |
| Aminophylline/Theophylline | CYP1A2 substrate; riluzole may increase theophylline levels. Monitor for toxicity. | Moderate |
| Omeprazole | CYP1A2 inducer; may decrease riluzole plasma levels, reducing efficacy. | Moderate |
| Rifampicin | Potent enzyme inducer; significantly decreases riluzole exposure. Avoid combination. | Major |
| Charcoal | Reduces absorption of riluzole if taken concomitantly. | Moderate |
| High-dose Paracetamol (Acetaminophen) | Potential additive risk of hepatotoxicity. Monitor LFTs closely. | Moderate |
| Other Hepatotoxic drugs (e.g., Statins, NSAIDs) | Increased risk of liver injury. Requires enhanced monitoring. | Moderate |
7. Patient Counselling
- DO take the tablet exactly as prescribed, twice daily.
- DO take it on an empty stomach (1 hr before or 2 hrs after food).
- DO keep all scheduled appointments for blood tests (liver function).
- DO inform all your doctors you are taking riluzole.
- DONT stop taking the medicine without consulting your neurologist.
- DONT take extra doses if you miss one. Take the next dose at the regular time.
- DONT consume alcohol.
- DONT start any new medicine (including OTC, herbal) without doctor's approval.
8. Toxicology & Storage
Overdose: Acute overdose may include: nausea, vomiting, ataxia, drowsiness, methemoglobinemia (bluish skin), hyperexcitability, coma, and potential acute hepatic necrosis.
Storage: Store below 30°C. Protect from light and moisture. Keep in the original blister pack until use. Keep out of reach of children.