Treatment of cystinosis with delayed-release cysteamine: 6-year follow-up.

Patients with nephropathic cystinosis are required to take 6-hourly immediate-release cysteamine (Cystagon®) to reduce disease progression. This arduous regimen affects quality of life, disrupts sleep, and may result in non-compliance with therapy. Enteric-coated cysteamine bitartrate (EC-cysteamine) was developed as a "proof-of-concept" formulation for twice-daily ingestion. Previous reports have shown this therapy to be effective up to a mean of 14 months. Two subjects (aged 13 and 15 years) received EC-cysteamine for 5-6 years at 60-65 % of their previous total daily dose of immediate-release cysteamine given at 6-h intervals. White blood cell (WBC) cystine levels were monitored every 1-3 months. The administration of EC-cysteamine did not result in any change in mean trough WBC cystine levels or any deterioration in the estimated glomerular filtration rate, thyroid, or liver function, suggesting that delayed-release, twice-daily EC-cysteamine is an effective long-term treatment alternative to immediate-release cysteamine given at 6-h intervals.