Insufficient effectiveness of 5-hydroxytryptamine-3 receptor antagonists due to oral morphine administration in patients with cisplatin-induced emesis

To compare the effect of 5-hydroxytryptamine-3 (5HT(3)) receptor antagonists in cancer patients receiving chemotherapy including cisplatin (CDDP), with or without sustained-release oral morphine (MS Contin; Shionogi Co, Osaka, Japan).

We retrospectively studied 58 lung cancer patients given chemotherapy including at least 50 mg/m(2) CDDP with 5-HT(3) receptor antagonists between January 1996 and December 1997. Number of vomiting episodes, average proportions of hospital-supplied meals consumed (0 to 100%, as an index of appetite), and nausea severity scores (0 to 2 points, subjective patient judgment) were compared between oral morphine-administered (+) and morphine-free (-) groups.

Sixteen morphine(+) and 42 morphine(-) cases were used. In cases of acute emesis (within 24 hours after CDDP injection), morphine(+) and morphine(-) groups were significantly different in number of vomiting episodes (1.25 and 0.14, respectively; P <.0001), appetite (58.13% and 90.24%; P <.0001), and nausea severity scores (1.63 and 0.62; P <.0001). In delayed-emesis cases (24 to 120 hours after CDDP), these groups differed significantly in number of vomiting episodes (1.94 and 0.43, respectively; P =.0001), appetite (23.13% and 52.08%; P <.0001), and nausea severity (1.38 and 0.91; P =.009). There were no significant differences in sex, age, anticancer drugs concurrent with CDDP, CDDP dose, corticosteroid administration, clinical stage, or type of 5-HT(3) antagonist.

These data suggest that morphine can markedly reduce the effectiveness of 5-HT(3) receptor antagonists in patients receiving chemotherapy that includes CDDP. These results require confirmation by reinvestigation of clinical data on the efficacy of 5-HT(3) receptor antagonists and by extensive prospective analyses.