Cocaine, used intravenously, increases the risk of infections, but its effe
cts on neutrophil phagocytosis have not been examined in vitro. Human neutr
ophils were suspended in cocaine hydrochloride 0, 1, 10, 50, 100 or 200 mu
g/ml in Hank's balanced salt solution to which was added a phagocytic meal
of killed Saccharomyces cerevisiae stained with the pH indicator dye bromcr
esol purple. Yeast per phagocytosing neutrophil and the percent neutrophils
phagocytosing yeast were reduced in neutrophils treated with cocaine 100 a
nd 200 mu g/ml (P < 0.05). When examined for percent of yeast phagocytosed
after 10 minutes, neutrophils treated with cocaine 1-200 mu g/ml demonstrat
ed a decrease (P < 0.05). However, at 60 minutes only neutrophils treated w
ith cocaine 50 and 100 mu g/ml still showed a decrease in percent of yeast
phagocytosed. Phagolysosomal acidification was impaired in neutrophils trea
ted with 50, 100 and 200 mu g/ml cocaine. Thus, cocaine inhibits neutrophil
phagocytosis and phagolysosomal acidification in vitro, offering a reason
for cocaine users/ abusers to have impaired host defense and to be potentia
lly at higher risk for infections.