- Neutrophil functions were studied in patients receiving calcium channel blockers : nifedipine, diltiazem or verapamil. Neutrophils from patients treated with nifedipine showed a significantly lower superoxide generation stimulated by phorbol myristate acetate (PMA) (50 ng mL -1 ), opsonized zymosan (1 mg mL -1 ) or formyl-methionyl-leucylphenylalanine (FMLP) (10 -7 M), whereas superoxide generation by neutrophils of patients receiving diltiazem or verapamil showed only a slight and insignificant reduction compared with controls. Similarly, chemotaxis towards 10 -7 M FMLP and phagocytosis were significantly lower in patients receiving nifedipine compared with controls and were only slightly reduced in patients receiving diltiazem or verapamil. Nifedipine was the most efficient drug in inhibiting the rise in intracellular calcium ion concentration ([Ca 2+ ] i ) when added in vitro and in neutrophils of patients receiving this drug, whereas verapamil had no significant effect. The correlation between the inhibitory effect of nifedipine on neutrophil function and the elevation of [Ca 2+ ] i suggests that nifedipine inhibits neutrophil functions through its effect on [Ca 2+ ] i . However, it is not the sole mechanism as superoxide generation induced by PMA, an agent that does not induce a rise in [Ca 2+ ] i , is also inhibited. The unique effect of nifedipine in reducing neutrophil functions in vivo suggests its clinical implications concerning response to acute ischaemic myocardial events.