Inhibition of neutrophil function by solvent of injectable sedatives- Effects of propylene glycol, ethanol and benzyl alcohol

Propylene glycol, ethanol and benzyl alcohol are usually included in the injection solutions of diazepam, flunitrazepam and others as solvents and/or pain relief agents. It was reported that diazepam and flunitrazepam inhibited oxidative burst of human neutrophils to produce O₂^-, H₂O₂ and other active oxygen species. However, the present study revealed that the solvents had far more potent inhibitory effects in this regard than diazepam and flunitrazepam themselves. The solvents reversibly inhibited phagocytosis and O₂^- production by neutrophils, and they were stimulated by both soluble stimulants, phorbol myristate acetate or laurate, and a particulate stimulant, serum opsonized zymosan, in a dose-dependent manner. Benzyl alcohol, which had the most potent effect among the solvents, appeared to inhibit the O₂^- generating enzyme NADPH oxidase directly, rather than by affecting intracellular calcium mobilization. Thus one should keep in mind such unexpected effects of the solvents included in solutions for injection.