We have read the letter of Dr. Ehrich with great interest [1].

We agree that the problem of non-compliance is of great importance in patients with cystinosis. It was also demonstrated in our study: only 5/22 patients took Cystagon® every 6 hours as it was prescribed. Therefore we examined morning PMN cystine content following a 6 and 9 hours night pause. Mean cystine content after 9 hours night break was above and not within the recommended value of 0.5 nmol cystine (or 1.0 half-cystine) per mg protein [2].

We recognize that the administration of Cystagon every 6 hours is a heavy burden for cystinotic patients and their parents. It should be indeed balanced against the benefit of better metabolic control of cystinosis. Some patients, however, prefer taking the drug during the night because of less disturbing side effects such as gastric discomfort and bad breath smell.

The development of new long-acting cysteamine preparations would be a considerable improvement for the treatment of patients with cystinosis.