The pharmaceutical and biological availability of commercial preparations of furosemide.

The pharmaceutical and biological availability of 8 commercial furosemide preparations (6 tablets and 2 preparations with modified release of active ingredient) have been investigated. Two of the tablet preparations showed different rates of drug release in vitro. Additionally they were found to differ significantly in their bioavailability with respect to the maximal plasma concentrations attained after oral administration to healthy volunteers. Bioavailability of the preparations with modified release properties--an enteric-coated tablet and a sustained release preparation in the form of a capsule containing diffusion pellets--was calculated to 80% of that of the rapid releasing tablet used as a standard. Correlations were obtained between the rate of dissolution measured with different techniques and the area under the plasma concentration time curve.