Concordance between substance P levels and antiemetic guidelines.

Practice guidelines now include an antagonist of the substance P/NK1 (neurokinin 1) receptor pathway as part of the standard antiemetic regimen for patients receiving highly, as well as certain moderately, emetogenic chemotherapy regimens. Accumulated laboratory data were used to determine the degree of concordance between substance P levels and the current antiemetic guidelines. Five blood samples were collected over 72 hours from 22 adult patients treated with cisplatin-containing chemotherapy regimens. Overall, the mean baseline substance P level was 318 pg/mL. Although increases in substance P were observed during both phases of the emetic response, analysis by least squares means grouped by cisplatin dosage and vomiting phase was significantly different (P< 0.0001). Preliminary analysis of substance P levels appears to provide additional justification for including the NK1 receptor antagonist in the current antiemetic practice guidelines. In addition, these data provide biochemical justification for the cisplatin dosage criterion used in clinical trials.