riluzole: clinical use

Prescribing considerations

• Specialist initiation is required; establish whether diagnosis and disease stage match the licensed ALS population.
• Review hepatic and renal status, pregnancy and breastfeeding before treatment.
• Assess swallowing ability and excessive salivation before selecting the orodispersible film; swallowing safety has not been evaluated in severe dysphagia or sialorrhoea.
• Consider formulation excipients, including fructose and sunset yellow in the orodispersible film and sorbitol in the suspension.

Contraindications and cautions

• Hypersensitivity to riluzole or formulation excipients
• Hepatic disease or baseline transaminases above three times the upper limit of normal
• Pregnancy
• Breastfeeding

Monitoring

• Measure serum transaminases, including ALT, before treatment and regularly afterwards.
• Monitor more frequently if ALT rises; discontinue if ALT reaches five times the upper limit of normal. Rechallenge is not recommended in this situation.
• Check a white-cell count promptly if fever develops and discontinue if neutropenia is confirmed.
• Investigate new dry cough or dyspnoea with chest imaging; discontinue immediately if findings suggest interstitial lung disease.

Clinical pharmacology

Riluzole is rapidly absorbed, extensively distributed, highly protein-bound and crosses the blood–brain barrier. CYP1A2-mediated oxidation followed by glucuronidation is the main metabolic pathway, and elimination is predominantly urinary as metabolites. Hepatic impairment substantially increases exposure.

Formulation and product differences

• Tablets are film-coated; high-fat food reduces their rate and extent of absorption.
• The orodispersible film dissolves on the tongue without liquid and can cause transient oral hypoesthesia. It should not be folded, chewed or spat out.
• The oral suspension must be shaken, measured with its oral syringe and can be given through specified silicone or polyurethane enteral tubes. It does not require dilution.
• The suspension and tablets have comparable overall exposure, although the suspension produces a higher peak concentration; a slightly greater risk of exposure-related adverse effects cannot be excluded.

Oral suspension

Route: Oral

Strengths: 5 mg/mL

Tablet

Route: Oral

Strengths: 50 mg