Lack of interaction between cefdinir and calcium polycarbophil: in vitro and in vivo studies

The effect of calcium polycarbophil on the absorption of cefdinir, cephalosporin derivative, was evaluated in both in vitro and in vivo studies. In the in vitro study, the release of cefdinir from a cellulose membrane in the presence or absence of metal cations was measured using the dissolution test procedure. In the in vivo study, volunteers and a randomized crossover design with two phases were used. In the first phase, the volunteers received 200 mg of cefdinir alone (Study 1); in the other phase, they received 200 mg of cefdinir and 1200 mg of fine calcium polycarbophil granules concomitantly (Study 2). The cefdinir concentrations in the samples or serum were measured by an UV-VIS spectrophotometer or high-performance liquid chromatography. Release in the presence of iron ions was slower than that in the absence of metal ions, however no difference was observed between release in the presence of calcium ions and that in the absence of metal ions. No difference was observed in AUC(0-10), C(max) and t(max) between Study 1 and Study 2. The absorption of cefdinir was not affected by co-administration of calcium polycarbophil. Moreover, the in vitro study on the release of drugs from a cellulose membrane may predict the absorption of a drug caused by the formation of chelate complexes between the drug and metal ions.