Decreased plasma levels of omeprazole after coadministration with magnesium aluminium hydroxide dry suspension granules

Plasma levels of omeprazole (OPZ) in Japanese male subjects were compared a fter a single oral administration of 20 mg of OPZ enteric-coated tablets wi th and without coadministration of Maalox(R) (MLX suspension) or Maalox(R) dry suspension granules (MLX granules). After coadministration of MLX granu les, plasma levels of OPZ markedly decreased, and aera under the blood conc entration-time curve (AUC) decreased to 26% of that of OPZ alone. In contra st, only a slight decrease in AUC was observed after coadministration of OP Z and MLX suspension. Both MLX suspension and MLX granules exhibited simila r degrees of the inhibitory effect on the renal excretion of levofloxacin. It was suggested that a specific and unexpected drug interaction occurred b etween OPZ enteric-coated tablets and MLX granules via a distinct mechanism from that reported for fluoroquinolones and MLX suspension.