Felbamate crystalluria].

Xavier Parent, Franz Schieffer

Service de biochimie, Hôpitaux civils de Colmar. xavier.parent@ch-colmar.rss.fr

Annales de biologie clinique 2010 Sep-Oct

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This report describes the case of an 11-year-old child, who presents crystalluria occurring after several years of treatment with antiepileptic felbamate (Taloxa®). The crystalline morphologies observed were very heterogeneous, long and thin needle shapped-crystals or even hairy crystals or large needle asymmetric crystals. Crystals showed an intense polarization and a strong tendency to aggregation. An infrared spectrum (KBr pellets) recorded in washed and dried urinary sediment demonstrated that these crystals are felbamate crystals. Crystal does not contain any Ca2+ and is not sensitive to pH changes suggesting that crystallization risk will not be affected by the potential association of felbamate with an inhibitor of carbonic anhydrase. After admission, creatinine level was in normal range but hematuria described by the child's mother could be symptomatic of even greater crystallization episodes and substantiate obstructive risk. A permanent good dilution of urine is the key measure to control risk of crystallization. Regular monitoring of urine specific gravity and urinary red cells by simple urine dipstick test can be proposed.