laboratory an animal investigations Talc Slurry Is an Effective Pleural Sclerosant in Rabbits* Richard W. Light, MD, FCCP; Nai-San Wang, MD; Catherine S. H. Sassoon, MD, FCCP; Steve E. Gruer, BS; and Francisco S. Vargas, MD, FCCP Insufflated talc is probably the most effective agent for creating a pleurodesis both in the clinical situation and in animals. However, the insufflation of talc requires an invasive procedure such as thoracoscopy or thoraco- tomy. Recently, there have been reports that talc in a slurry was effective in the clinical situation. The objec- tive of this project was to determine whether talc in a slurry at varying doses is an effective sclerosant in an experimental model in rabbits. Talc, 50, 100, 200, ai,d 400 mg/kg, in a 2-mL slurry was injected intrapleurally through a small catheter in male rabbits. Eleven rabbits received each dose. Twenty-eight days after the instil- lation, the animals were killed. The pleural spaces were assessed grossly for evidence of pleurodesis and micro- scopically for evidence of fibrosis and inflammation. he search for the ideal agent for creating a pleu- rodesis in patients with chronic pleural effusions or pneumothorax continues. The first agents used for this purpose were the antineoplastic agents such as nitrogen mustard.' Subsequently it became apparent that these agents produced a pleurodesis not due to their antineoplastic actions but rather because they produced pleural fibrosis. Following this observation, agents such as quinacrine2 and tetracycline,3 which produced pleural fibrosis, gained acceptance. In the 1980s, tetracycline was the agent most commonly used due to its effectiveness in an animal model,4 its effectiveness in humans,5 its low cost, its ease of ad- ministration, and its wide availability. However, in the early 1990s, the company that had been manufacturing parenteral tetracycline ceased to produce it because of more stringent manufactur- ing requirements for parenteral antibiotics. This led *From the Department of Medicine of the Veterans Affairs Medical Center Long Beach, Calif, and the University of Cali- fornia, Irvine (Drs. Light, Wang, Sassoon, and Gruer), and the Instituto de Coracao of the Faculty of Medicine of the Univer- sity of Sao Paulo, Brazil (Dr. Vargas). Supported in part by research grants from the Department of Veterans Affairs. Manuscript received September 12, 1994; revision accepted No- vember 30. Reprint requests: Dr. Light (111P), VA Medical Center, Long Beach, CA 90822 1702 The degree of pleurodesis (on a scale of 0 to 4) after the injection of 50, 100, 200, and 400 mg/kg of talc was 1.1±0.9, 1.5± 1.1, 2.7±0.6, and 3.4±0.5, respectively. The degree of microscopic fibrosis similarly increased with increasing doses of talc. These scores were similar to those we have reported with the tetracycline deriva- tives. In contrast to the results with tetracycline deriv- atives, none of the rabbits developed fibrothorax or he- mothorax. From this study, we conclude that talc in a slurry is a very effective pleural sclerosant in rabbits and does not produce hemothoraces as do the tetracycline derivatives. (CHEST 1995; 107:1702-06) Key words: pleural effusion; pleurodesis; pneumothorax; talc to a scramble to find a substitute. The leading candidates were the tetracycline derivatives minocy- cline6'7 and doxycycline,8'10 bleomycin,11'12 aero- solized talc,13'14 and Corynebacterium parvum.'516 However, there are problems with all the above agents. In the experimental situation, the intrapleu- ral administration of minocycline or doxycycline, particularly at higher doses, leads to the development of marked atelectasis, hemothorax, and a high mor- tality.6 Bleomycin is very expensive and since it does not produce a pleurodesis in rabbits with a normal pleura,17 it certainly should not be used for pneu- mothorax or benign pleural effusions. Insufflated talc is probably the best agent for producing pleurodesis in patients with malignant pleural effusions'8 or pneumothorax'9 and it is very effective in the animal, but it must be administered in conjunction with an invasive procedure (thoracoscopy or thoracotomy). Corynebacterium parvum is not available in the United States. Another possible alternative is talc in a slurry. Four series have demonstrated that it is highly effective in treating malignant pleural effusions.'9-22 The objec- tive of the present study is to determine whether talc in a slurry is an effective sclerosant in an experimen- tal model in rabbits and if so to define the appropri- Laboratory and Animal Investigations Downloaded From: http://journal.publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21715/ on 04/12/2017