Phagocytosis and bactericidal activity of human leucocytes under influence of antimalarial drugs

The phagocytic and bactericidal activity of human peripheral blood leucocytes under the influence of commonly used antimalarial drugs was studied. The following drugs were used: chloroquine diphosphate, quinine HCl, mefloquine HCl, proguanil HCl, cycloguanil, pyrimethamine and tetracycline HCl. It was found that leucocytes treated with mefloquine, proguanil and cycloguanil at concentrations higher than 0.5 mg/litre showed reduced phagocytic activity against Staphylococcus aureus. None of the other drugs tested had any inhibitory effect on phagocytosis. The bactericidal ability of the leucocytes was not affected by any of the drugs. It is concluded that none of the commonly used antimalarial drugs, at concentrations obtainable in malaria prophylaxis and therapy, have any undesirable effect on the bactericidal activity of human leucocytes.