Clarithromycin dry syrup, a new drug preparation, was clinically evaluated in the pediatric field and the following results were obtained: 1. Absorption and excretion In infants administered with single oral dose of 5 mg (potency)/kg and 10 mg/kg, the Cmax was 2.26 +/- 0.42 and 3.23 micrograms/ml; Tmax, 1.6 +/- 0.1 and 2.0 hours; T 1/2, 3.89 +/- 0.52 and 2.06 hours; AUC (0-infinity), 13.48 +/- 1.93 and 13.84 micrograms.hr/ml, respectively. Urinary concentrations peaked in 2-4 hours after administration at 5 mg/kg and 0-2 hours at 10 mg/kg. Urinary recovery rates in the first 6 hours were 25.8 +/- 3.9% at 5 mg/kg and 20.7% at 10 mg/kg. 2. Clinical results The clinical efficacy of the drug was evaluated in 150 patients with various infections. Clarithromycin dry syrup was administered to all the patients at daily doses of 10-15 mg/kg divided into 2-3 equal doses. The overall clinical efficacy rate was 98.0%, and this drug was effective in 98.9% of 90 patients for whom the causative pathogens were identified and in 96.7% of the other 60 patients for whom the causative pathogens were unknown. The bacteriological eradication rate was 88.5%. The efficacy and eradication rates for 19 patients who had not responded to previous chemotherapy that lasted for more than three days were 94.7% (18/19) and 75.0%, respectively. Side effects occurred in 4 (2.4%) of 169 patients subjected to safety analyses, but none was serious. As to abnormal laboratory test results, moderate increases of eosinophils and elevations of transaminases were observed in 5.9% of the cases. No particular and serious problems were associated with administration of this drug. Based on the above results, clarithromycin dry syrup is considered to be very useful and have a good compliance at a daily dose of 10-15 mg/kg divided into 2-3 doses.