In this study we determined the pharmacokinetics of higher IV doses of ciprofloxacin (Cipro) in patients with pleuro-pulmonary diseases undergoing treatment for various bacterial infections. Cipro IV was infused over 30-45 min in 11 patients (seven on 400 mg bid, four on 200 mg bid). Blood samples were taken at intervals of up to 4 h and assayed for Cipro using the HPLC method. The 'mean' peak concentration (C(max)) was 6.9 +/- 2.2 (S.D.) and 11.8 +/- 5.2 (S.D.) for the 200 and 400 mg groups, respectively. The mean concentrations at 1.5 h were 1.2 and 2.6 mg/l and the area under the curve in 0-4 h was 4.6 +/- 0.9 (S.D.) and 7.5 +/- 2.4 (S.D.), respectively for the 200 and 400 mg groups. Steady state serum concentrations of 400 mg were approximately double those for the 200 mg group. IV 200 mg did not reach the required levels to cover the minimum inhibitory concentrations (MICs), whereas, 400 mg IV dose clearly will provide an improved coverage for the commonly encountered organisms with MICs in the 1-4 mg/l range.