EFFECTS OF ERYTHROMYCIN ON THE RABBIT PLEURA - ITS POTENTIAL ROLE AS A PLEURAL SCLEROSANT

Tetracycline (TCN) has been considered the agent of choice for pleurod esis in patients with symptomatic malignant pleural effusions and recu rrent pneumothoraces. However, the intravenous form of TCN used for pl eurodesis is no longer available. Erythromycin, like TCN, often produc es irritation when administered intravenously. In view of these irrita nt properties, we tested the effect of erythromycin as a pleural scler osant in rabbits as compared with TCN. Normal saline was used as a con trol. Adult rabbits weighing 2.5 to 3.0 kg underwent sterile placement of a silastic pleural tube in the right pleural space. Erythromycin ( n = 17) or TCN (n = 6), each in doses of 35 mg/kg in 2 ml saline, was administered via the tube. Control animals (n = 6) received 2 mi salin e. The chest tubes were left in place for removal of pleural fluid and to maintain lung expansion. Animals were killed 8 d after receiving t he various treatments, and their pleural surfaces were examined grossl y and histologically. Numerous adhesions were present between the visc eral and parietal pleurae in all animals receiving erythromycin and TC N, but not in those receiving saline. On light microscopy, pleurae tre ated with erythromycin or TCN were histologically identical, showing i nflammation, edema, and fibroblast proliferation in the submesothelial tissues. The saline-treated animals had a normal pleura. Because eryt hromycin produced pleural inflammation and adhesions within 8 d of tre atment, we propose that it may have a potential role as a pleural scle rosant.