The effect of corticosteroids on pleurodesis induced by doxycycline in rabbits

To determine if the administration of systemic corticosteroids diminishes the effectiveness of the pleurodesis induced by the intrapleural injection of doxycycline.

Thirty New Zealand white male rabbits were classified into three groups (n = 10 rabbits), all of which received doxycycline, 10 mg/kg intrapleurally, in a volume of 2 mL. Rabbits in the control group received only the intrapleural injection of doxycycline; the steroid-once group received triamcinolone, 0.8 mg/kg IM, 24 h before the intrapleural injection; and the steroid-weekly group received triamcinolone, 0.8 mg/kg IM, 24 h before the intrapleural injection and weekly over the next 3 weeks. All rabbits had a chest tube placed before the intrapleural administration of doxycycline and underwent pleural fluid aspiration twice daily. The rabbits were killed after 28 days, and the pleura and lungs were examined macroscopically and microscopically.

The administration of corticosteroids resulted in both a significant decrease in the macroscopic adhesion score (p < 0.001) and a tendency toward a decreased microscopic fibrosis score (p = 0.056) after 28 days. Animals receiving weekly corticosteroid injections had lower scores than animals receiving only one injection.

This study demonstrates that the administration of corticosteroids (triamcinolone, 0.8 mg/kg) 24 h before the intrapleural injection of doxycycline, 10 mg/kg, decreases the effectiveness of pleurodesis in rabbits. Weekly injections decreased the effectiveness even more. If these results can be extrapolated to humans, efforts should be made to minimize the administration of exogenous corticosteroids when pleurodesis is attempted.