Effects of magnesium-aluminum hydroxide and calcium carbonate antacids on bioavailability of ofloxacin.

The effects of 15- and 5-ml doses of magnesium-aluminum hydroxide (MAH) and calcium carbonate (CC) antacids, respectively, on the bioavailability of ofloxacin after single oral 400-mg doses of ofloxacin were investigated in a 32-subject, randomized, crossover, open-label study. On four separate occasions, subjects received ofloxacin alone or antacid 24 h before, 2 h before, or 2 h after ofloxacin administration (n = 16 for each antacid). CC administration had no significant effect on the rate and extent of ofloxacin absorption regardless of the timing of antacid administration. A small but significant negative effect of MAH administration 2 h before ofloxacin administration was noted as evidenced by area under the curve and peak concentration in plasma data. Simultaneous administration of ofloxacin with either antacid was not investigated in this study. It appears that MAH and CC antacids in the doses used in this study generally do not interfere in a clinically significant manner with the bioavailability of ofloxacin, provided that an interval of at least 2 h separates the administration of these products.