Clinical application of an enzyme immunoassay for cholecystokinin-like immunoreactive substance for determination of the human plasma levels: the effect of metoclopramide on gastrointestinal peptides and stress-related hormones.

Metoclopramide, a prokinetic drug, is widely used to treat vomiting and nausea. Delayed gastric emptying and continual stress are considered important factors, among others, that induce nausea and vomiting. One gastrointestinal motility regulatory factor has been assumed to be the induction of changes in the levels of peptides such as gastrin, somatostatin, motilin, and cholecystokinin (CCK) in plasma. In contrast, adrenocorticotropic hormone (ACTH) and cortisol are used as indicators of stress. Here, we studied the effects of metoclopramide on human plasma gastrin-, somatostatin-, motilin-, and CCK-like immunoreactive substances (ISs) and ACTH-IS and cortisol under stress conditions using repetitive blood sampling in healthy subjects. Metoclopramide hydrochloride at a dose of 30 mg or placebo was orally administered to five healthy male volunteers. Blood samples were taken before and 20, 40, 60, 90, 120, 180, and 240 min after administration, subject to extracting procedures, and submitted to a highly sensitive enzyme immunoassay system. A single administration of metoclopramide caused significant increases in plasma somatostatin-IS levels compared with the placebo. Metoclopramide significantly decreased plasma gastrin- and suppressed ACTH-IS and cortisol levels compared with the placebo. We hypothesize that metoclopramide might have an accelerating gastric-emptying effect and a modulatory effect on the hypothalamo-pituitary-adrenal (HPA) axis and the autonomic nervous function. These effects might be beneficial in stress-related diseases, which suggest that this medicine has clinicopharmacological activities.