Antitumor effects of dopaminergic blockers in mice bearing Ehrlich tumors.

We determined the effect of 13 days of treatment with 2.0 mg/kg haloperidol, 30.0 mg/kg metoclopramide or 4.0 mg/kg domperidone on the number of tumor cells of mice bearing Ehrlich ascites carcinoma. The three dopaminergic blockers significantly reduced the number of tumor cells of experimental mice. The mean +/- SEM number of tumor cells x 10(6)/ml saline lavage was 25.5 +/- 5.9 for the haloperidol group, 36.8 +/- 4.7 for the metoclopramide group, 25.3 +/- 3.5 for the domperidone group and 54.0 +/- 9.0 for the control mice (treated with 0.9% NaCl). In a second experiment, treatment with 0.5 and 2.0 mg/kg haloperidol showed that the antitumor effect of this drug was dose dependent. The possible mechanisms underlying these results (such as an increase in prolactin levels or a direct action of these drugs on lymphocytes) are discussed in light of the specific pharmacological properties of each dopaminergic blocker.