The action of the NK1 tachykinin receptor antagonist, CP 99,994, in antagonizing the acute and delayed emesis induced by cisplatin in the ferret.

1. The anti-emetic effects of the NK1 tachykinin receptor antagonist, CP 99,994 (10 mg kg-1) were investigated in the ferret using a cisplatin-induced acute (day 1) and delayed (day 2 and 3) retching and vomiting model. 2. With a single cisplatin (10 mg kg-1) emetogenic challenge, the i.p. administration of CP 99,994 given as a single injection immediately following the first emetic episode, promptly abolished the retching and vomiting for a 4 h period. CP 99,994 was as efficacious as ondansetron (1.0 mg kg-1). The general toxicity of cisplatin 10 mg kg-1 precluded its use in studies of delayed emesis. 3. With a single cisplatin (5 mg kg-1) emetogenic challenge, the single administration of either CP 99,994 (10 mg kg-1) or ondansetron (1.0 mg kg-1) immediately following the first emetic episode markedly reduced or abolished the retching and vomiting for 4 h. Such single treatments failed to modify significantly the intensity of delayed emesis appearing on the second and third day. 4. With a cisplatin (5 mg kg-1) emetogenic challenge, administration of CP 99,994 (10 mg kg-1) at 8 hourly intervals, the first injection being administered 30 s post cisplatin, was associated with 4 or more abolitions of emesis during both the acute and delayed phase. A 4 hourly administration of CP 99,994 for 20 h during delayed emesis completely abolished the retching and vomiting. 5. It is concluded that cisplatin 5 mg kg-1 provides an emetogenic challenge causing an acute and delayed phase of retching and vomiting and that CP 99,994 can abolish both phases. The results may be relevant to the understanding and treatment of chemotherapy-induced emesis in man.