Gastrointestinal distress resulting from drug intake is often remedied by administering the drug with antacids. However, antacids have been shown to modify the absorption and excretion of many drugs. This study was designed to delineate the effects of aluminium and magnesium hydroxide antacid suspension (Maalox) on the pharmacokinetics of flurbiprofen. Since this drug is often used in the elderly, not only young healthy but also geriatric healthy male volunteers participated in the study. A group of twelve young and a group of seven geriatric volunteers received, in a crossover design, a single oral dose of 100 mg of flurbiprofen with and without Maalox. A non-stereospecific assay was used to determine the total (R+S enantiomers) of flurbiprofen in plasma. The relative pharmacokinetic parameters of total flurbiprofen determined from plasma samples were and . The results indicate that the co-administration of Maalox with flurbiprof(k had no effect on the rate and extent of total flurbiprofen absorption in young volunteers. In geriatric volunteers, the results indicate no effect of the antacid on the extent of drug absorption. There was a trend for lower plasma concentrations of total flurbiprofen with antacid in the geriatric group and hence a reduction in rate of flurbiprofen absorption although differences were not significant. The study also included a steady state determination of the influence of antacid administration on flurbiprofen pharmacokinetics. The group of young volunteers received, from Day 3 to Day 8, 100 mg of flurbiprofen every 12 h with and without Maalox. Steady state pharmacokinetics were similar to those after single administration: the antacid had no effect on either the rate or the extent of total flurbiprofen absorption.