Study objective: To determine whether the administration of antiinflammatory drugs interferes with experimental pleurodesis induced by silver nitrate or talc.
Study design: Two groups of 30 white New Zealand rabbits were scheduled to receive an intrapleural injection of 0.5% silver nitrate or 400 mg/kg of talc. Each group was further classified into three subgroups (10 animals each), which received the following: (subgroup 1) the sclerosing agent only, (subgroup 2) the sclerosing agent plus 1 mg/kg of methylprednisolone, and (subgroup 3) the sclerosing agent plus 1.1 mg/kg of diclofenac sodium. The antiinflammatory agents were administered IM 24 h before the sclerosing agent and daily during the first week, followed by once-weekly injections until death at 28 days. At this time, the pleural cavity was macroscopically evaluated, and samples of pleura and lungs were collected for further microscopic examination.
Measurements and results: The degree of pleural adhesions was higher after silver nitrate administration (p = 0.019). No reduction in the adhesions was observed after administering antiinflammatory drugs to this group (p > 0.05). Conversely, the adhesion score was significantly reduced after administration of both prednisolone (p = 0.028) and diclofenac (p = 0.032) to the animals that received talc. Administration of the antiinflammatory agents did not influence microscopic pleural or lung changes induced by silver nitrate or talc.
Conclusion: These results show that the sustained systemic administration of antiinflammatory agents (steroidal or nonsteroidal) reduces the degree of pleural adhesions in animals with talc-induced pleurodesis but does not affect silver nitrate-induced pleurodesis. Extrapolation of these results to humans suggests that the use of antiinflammatory drugs should be avoided in patients with talc-induced pleurodesis and that appropriate clinical studies with silver nitrate should be conducted in patients chronically treated with these antiinflammatory agents.