COX inhibition primes human whole blood to kill bacteria. Peripheral blood of 8 healthy male volunteers between the ages of 25 and 50 was taken before and 1 hour after ingestion of 500 mg naproxen and incubated ex vivo with opsonized GBS. After 60 minutes aliquots were taken to determine (A i) numbers of viable bacteria determined by overnight incubation on agar plates or (A ii) leukocyte NADPH oxidase activity. Blood from volunteers taken naproxen was further incubated with (B i-iii) penicillin (0.075 μg/mL) to determine NSAID inhibitory/additive effects on bacterial killing with antibiotics. (C) Blood was also treated 400 μM naproxen for 30 minutes and stimulated with FAMSE labeled S pneumoniae (ST193) 5 minutes to determine bacterial phagocytosis and to show that (D) NSAIDs do not interfere with opsinization of bacteria. Data were analyzed by paired Student t test. * values represent P < .05 and ** values represent P < .01.