5-Hydroxyindoleacetic acid excretion following combination chemotherapy with cyclophosphamide, epirubicin and 5-fluorouracil plus ondansetron compared to ondansetron alone.

The aim of the work was to evaluate the impact of cyclophosphamide and ondansetron on serotonin metabolism measured by urinary 5-hydroxyindoleacetic acid (5-HIAA) excretion. The pattern of urinary 5-HIAA excretion was analysed within 24 h following cyclophosphamide, epirubicin and 5-fluorouracil (FEC) chemotherapy (n = 14), ondansetron as single agent (n = 31), and in a control group (n = 62). 5-HIAA was measured by a fluorescence/polarisation immunoassay. Both FEC and ondansetron alone induced a significantly higher 5-HIAA increase following the first 12 h after drug administration when compared to the control group. The comparison of quantitative variables of 5-HIAA excretion between FEC and ondansetron failed to reveal any statistical differences. Cyclophosphamide-based chemotherapy is associated with only minor increases of 5-HIAA excretion. Analysis of 5-HIAA excretion does not help in the description of the pathophysiology of cyclophosphamide-induced emesis. In contrast to experimental data, serotonin 3 receptor antagonism with ondansetron induces an increase of 5-HIAA excretion in humans.