Pranlukast is a novel LTD4 antagonist under development for the treatment of asthma. To assess the effect of age, the pharmacokinetics of pranlukast were studied in healthy young (9 females, 10 males, mean 30 years) and elderly subjects (9 per sex, mean 70.4 years). After an overnight fast volunteers were given 300 mg of pranlukast orally, 30 min after a light breakfast. Serial blood samples were collected for 24 hs, and the plasma was assayed by HPLC/UV. Pranlukast was well tolerated by the volunteers. The resultant mean plasma concentration vs. time data were very similar for both age groups. The estimated geometric mean AUCO-t and Cmax ratios (95% CI in parentheses) for elderly : young were 1.00 (0.71, 1.41) and 0.93 (0.66, 1.33), respectively. Median Tmax occurred at 4.5 h in both age groups. There were no significant differences observed in the pharmacokinetics of pranlukast between healthy young and elderly subjects. On stratifying the young and elderly data with respect to gender, no marked differences were observed between male and female subjects in the mean pharmacokinetic parameters of pranlukast, and the respective plasma concentrations profiles were very similar.