Reversible granulocytopenia in association with riluzole therapy

OBJECTIVE: To report a case of severe neutropenia developing in association with riluzole 200 mg/d. CASE SUMMARY: A 63-year-old woman with amyotrophic lateral sclerosis (ALS) prese nted with nausea, anorexia, and fever two weeks following inadvertent dose escalation of riluzole from 100 to 200 mg/d. Granulocytopenia was diagnosed and evaluation for a possible causative infectious process was negative; r iluzole was considered a possible offender. Blood counts returned to normal with discontinuation of riluzole and administration of filgramstim. DISCUSSION: Riluzole is a glutamate release inhibitor used in the treatment of ALS, a devastating, progressive neurodegenerative disorder affecting mo tor neurons. A variety of adverse effects have been described with riluzole therapy, most commonly dizziness and gastrointestinal disorders. In this p atient, multiple investigations failed to reveal an infectious cause or oth er drug-induced cause for the granulocytopenia. CONCLUSIONS: Granulocytopenia has been reported as an adverse effect of ril uzole but is not a complication well known to clinicians, and there are no detailed reports published in the literature. In this patient, several line s of evidence raise the possibility of a causal relationship between riluzo le and granulocytopenia.