Effect of chemical structure on the release of certain propionic acid derivatives from their dosage forms.

The aim of this study was to investigate the relationship between the chemical structure and release properties of certain drug products. Propionic acid derivatives were used as a model. These include ibuprofen (I), ketoprofen (K), tiaprofenic acid (T), flurbiprofen (F), and naproxen (N). They are all aryl derivatives of propionic acid and differ only in the aryl group. Such an aryl group may be either isobutylphenyl, benzoylphenyl, benzoylthienyl, fluorobiphenyl, or methoxynaphthyl group in I, K, T, F, and N, respectively. Three dosage forms were selected for this study: capsules, suppositories, and creams. The release of propionic acid derivatives from the capsules and suppositories decreased in the order ibuprofen > tiaprofenic acid > ketoprofen > flurbiprofen > naproxen, and for the creams the release decreased in the order ibuprofen > tiaprofenic acid > flurbiprofen > ketoprofen > naproxen. The difference in drug release in the first case was attributed to the difference in the chain length, and in the creams which are composed of two phases, the partition coefficient was found to affect the drug release. The molecular weight of the drug had no effect on the release. The drug release from different dosage forms was not affected after 1 month storage.