Effects of cilostazol, a cyclic nucleotide phosphodiesterase III inhibitor, on substance P-induced airflow obstruction and airway microvascular leakage in guinea pigs.

We studied the effect of cilostazol, a cyclic nucleotide phosphodiesterase (PDE) III inhibitor, on a substance P (SP)-induced increase in lung resistance and in airway microvascular leakage in guinea pigs in vivo. Four minutes after intravenous (i.v.) administration of cilostazol (1.5 and 5 mg/kg) or vehicle, Evans blue dye (20 mg/kg) was given i.v. One minute later, 30 nmol/kg SP was administered i.v. The SP-induced increase in lung resistance was measured for 6 min. Following the measurement of lung resistance, microvascular leakage at the trachea, main bronchi and intrapulmonary airways was also examined. Cilostazol attenuated the SP-induced increase in lung resistance, with a significant inhibition at the concentration of 5 mg/kg. Five milligrams per kilogram cilostazol also significantly inhibited SP-induced Evans blue dye extravasation at the trachea and main bronchi. These results suggest that cilostazol might reduce airflow obstruction which is seen in diseases such as asthma through attenuation of bronchoconstriction and, possibly, airway edema resulting from airway microvascular leakage in man.