Cysteamine dose regimen
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KeywordsCysteamine Cystin content Cystinosis
In their article on a strict cysteamine dose regimen for children with cystinosis, Levtchenko et al. reported that the mean morning polymorphonuclear (PMN) cystine content after a 9-h-long interval following the evening cysteamine dose was significantly higher than following a 6-h interval between doses . These results are of clinical importance and are supported by J. Schneider et al. on plasma cysteamine concentration and PMN cystine content analysis .
On the basis of their data the authors concluded that patients should adhere strictly to a 6-hourly intake of cystagon. Assuming that a patient would take cystagon at 5-h intervals during the day, with a 9-h interval between the evening dose and the one the following morning, it is obvious that these patients would have a slightly higher PMN cystine content for 3 of the 24 h compared to those children taking cystagon exactly every 6 h. However, even with this higher PMN cystine content for these 3 h, the levels would remain below the critical value of 1 mmol/mg protein cystine.
The benefit of a constantly lower cystine level – achieved at the cost of sleep disruption – has to be balanced against patient non-compliance. Several groups have reported that non-compliance by patients with cystinosis may occur in almost 50% of the patients, mainly because of the side effects of cystagon. Superimposing a strict interval of a 6-hourly drug intake will interfere with sleep and may increase non-compliance even more.