The pharmacokinetics of clarithromycin after oral administration of clarithromycin granules for suspension formulation were investigated in adult volunteers and pediatric patients. A 250mg single dose study conducted in adults revealed that the extent of absorption of clarithromycin from the suspension formulation was not significantly different from that of the reference tablet formulation, whereas the extent of formation of the active 14-hydroxy (14-OH) metabolite was significantly lower with the suspension formulation. In addition coadministration of the suspension formulation with food did not significantly alter the extent of absorption of clarithromycin or formation of the 14-OH metabolite. A single/multiple dose study conducted in adults revealed a delay in the time to attain peak plasma clarithromycin and 14-OH metabolite concentrations after suspension administration as compared with data obtained after tablet administration in previous studies. Steady state was achieved by Dose 5 in the multiple dose phase (250 mg every 12 hours for seven doses). In addition the mean plasma concentration-vs.-time data after suspension administration compared favorably with that noted after multiple oral dose administration of 250-mg tablets in adults. A single/multiple dose study conducted in pediatric patients revealed that coadministration of the suspension formulation with food did not significantly alter the extent of absorption of clarithromycin or formation of the 14-OH metabolite. During the multiple dose phase (7.5 mg/kg every 12 hours for 4 or 5 days), mean plasma concentration-vs.-time data compared favorably with that noted after multiple oral dose administration of 250-mg and 500-mg tablets in adults. Substantial steady state penetration of clarithromycin and its 14-OH metabolite was noted in a middle ear effusion penetration study conducted in pediatric patients. The mean ± SD ratios of middle ear effusion:serum concentrations of clarithromycin and 14-OH-clarithromycin were 2.48 ± 3.57 (mean ± SD) and 1.73 ± 1.40, respectively. These values are consistent with or superior to those observed for a wide variety of antimicrobials similarly studied.