COMPARISON OF SILVER-NITRATE AND TETRACYCLINE AS PLEURAL SCLEROSING AGENTS IN RABBITS

The ideal agent to produce pleurodesis has not been identified. Tetrac ycline, the drug used most commonly in the 1980s, is no longer availab le. Talc either aerosolized or in a slurry is the agent used most comm only at the present time, but there are concerns about its safety, Ano ther possibility is silver nitrate, which was widely used in the past, but was abandoned on account of side effects, We hypothesized that lo wer concentrations of silver nitrate than had been used in the past wo uld be effective in creating a pleurodesis in rabbits. The following m edications in a total volume of 2 mL, were instilled intrapleurally in three groups of ten anesthetized rabbits: 0.25% or 0.50% silver nitra te and 35 mg/kg tetracycline. Twenty-eight days after the injection, t he animals were sacrificed and the pleural spaces were assessed grossl y for evidence of pleurodesis and microscopically for evidence of fibr osis and inflammation. The intrapleural injection of 0.50% silver nitr ate produced an effective pleurodesis. The mean degree of gross pleuro desis in the rabbits that received 0.50% silver nitrate (3.4+/-1.2) di d not differ significantly from that of the rabbits that received tetr acycline (3.5+/-0.7) (scale 0 to 4). The mean degree of microscopic pl eural fibrosis in the rabbits that received 0.50% silver nitrate (3.4/-0.7) did not differ significantly from that of the rabbits that rece ived tetracycline (3.9+/-0.3). However, 0.25% silver nitrate was ineff ective in creating pleural fibrosis,either grossly or microscopically. No rabbits died after the intrapleural injection of the drugs, There were no observed side effects after the injection of silver nitrate. T he present sturdy demonstrates that 0.50% silver nitrate instilled int o the pleural space is an effective agent for producing pleurodesis in the rabbit; its effect is comparable to tetracycline 35 mg/kg. This a gent should be compared with tetracycline derivatives and talc in stud ies in humans.