Abstract
A three-compartment in vitro transport model, consisting of two aqueous compartments (buffered at pH 1.2 and 7.4) separated by a thin, olive oil-impregnated Millipore membrane, was employed to study the transport kinetics of four drugs in the absence and presence of the complexing agent, caffeine. The test drugs under investigation were salicylic acid, acetylsalicylic acid, dehydroacetic acid, and ethyl p-hydroxybenzoate. The apparent first-order transfer rate constants obtained for the drugs alone were found to correlate well with reported in vivo apparent first-order absorption rate constants. In the presence of caffeine the rate of transfer of all of the test drugs was significantly reduced. Calculated in vitro transport rate constants were found to correlate well with reported in vivo absorption rate constants for the drug-caffeine complexes.
