Single-dose versus two-dose dexamethasone effects on lung inflammation and airway reactivity in meconium-instilled...

Two doses of the corticosteroid dexamethasone may alleviate meconium-induced acute lung injury more effectively than a single dose. Meconium-instilled rabbits intravenously received dexamethasone (0.5 mg/kg) at one dose 0.5 hours after meconium instillation or at two doses 0.5 hours and 2.5 hours after meconium instillation or were left without treatment, and were oxygen-ventilated for additional 5 hours. At the end of experiment, lungs and trachea were excised. Two doses of dexamethasone effectively diminished meconium-induced lung edema, tracheal hyperreactivity to histamine, neutrophil count in bronchoalveolar lavage fluid, and decreased oxidative modifications of proteins and lipids in lung homogenate compared with the non-treated group. Single-dose dexamethasone also reduced lung edema, lung neutrophils, and tracheal hyperreactivity to histamine, but these effects were weaker than those after two-dose dexamethasone. We conclude that two-dose dexamethasone is superior to single-dose dexamethasone in prevention lung injury in meconium-instilled rabbits.