Systemic absorption of tetracycline and lidocaine following intrapleural instillation.

Seven patients with symptomatic pleural effusions (six) and recurrent pneumothorax (one) underwent attempted pleurodesis using tetracycline. Lidocaine (150 mg), followed immediately by tetracycline (20 mg/kg), was instilled into the pleural space through a chest tube. Venous blood was obtained at 0, 15, 30, 60, and 120 minutes following instillation in order to determine concentrations of lidocaine and tetracycline. The mean peak serum concentration of lidocaine was 1.3 mu/ml +/- 0.4 microgram/ml (mean +/- SE) (range, 0.3 microgram/ml to 3.2 microgram/ml), and the mean time to peak serum concentration of lidocaine was 86 +/- 13 minutes. The mean peak serum concentration of tetracycline was 3.6 microgram/ml +/- 0.9 microgram/ml (range, 1.0 microgram/ml to 5.0 micrograms/ml), and the mean time to peak serum concentration of tetracycline was 96 +/- 16 minutes. Therapeutic serum concentrations of lidocaine were found in four of the seven patients and therapeutic serum levels of tetracycline in four of five patients. With systemic absorption of lidocaine and tetracycline following intrapleural instillation, patients are at risk for potential toxic effects. If lidocaine is used in a dosage of less than 3 mg/kg, toxic levels of the drug are unlikely to occur. Furthermore, use of tetracycline or lidocaine in pleurodesis is contraindicated in patients with known sensitivity to the drugs.