The effect of flurbiprofen on the responses to frusemide in healthy volunteers.

Ten subjects participated in a four-way, open, crossover study to investigate the effect of frusemide, flurbiprofen, flurbiprofen plus frusemide, and placebo on urinary volume, sodium, and potassium. Compared with placebo, flurbiprofen was shown to significantly reduce all three parameters. The diuretic effect of frusemide was reduced by the addition of flurbiprofen but not to a statistically significant degree. The reduction was less than in previous reports using indomethacin. As flurbiprofen is a more potent inhibitor of prostaglandin synthesis than indomethacin, these data cast doubt on the theory that nonsteroidal anti-inflammatory drugs antagonize the action of diuretics by prostaglandin synthetase inhibition. The methods for assaying the two drugs are described. A pharmacokinetic explanation of the reduction of the diuretic effects of frusemide by flurbiprofen was sought but not found.