Adverse reactions to oral cysteamine use in nephropathic cystinosis.

Cysteamine (2-aminoethanethiol) has been given orally to 19 patients with nephropathic cystinosis for periods of 8-24 months in doses ranging from 50 to 70 mg base/kg/day. Adverse reactions were noted in 3 patients early in the study when a rapidly increasing dosage schedule was followed. The reactions included hyperthermia, lethargy and rash. These reactions were not seen when patients were started on a very low dosage which was increased gradually at 3-week intervals to a level which depleted leukocytes of about 90% of their free cystine. All three reactions resolved within 24 h or cessation of therapy and in these cases successful readministration of drug was achieved. Chronic cysteamine administration to pediatric patients with cystinosis is feasible. The efficacy of this therapy is still being evaluated.