In vitro evaluation of magaldrate antacid efficacy in the presence of some drugs and its effect on their dissolution rates: Part I.

A comparison of the antacid efficacy of magaldrate powder and its dosage forms on an equal weight basis by an in vitro technique revealed that: suspensions > chew tablets > powder. This was also evidenced by acid neutralizing capacity test USP XXIII, which also showed that riopan and rioplus suspensions were equipotent. All tested doses of different antacid dosage forms were found to regulate acid level to pH 3.0 within 10 seconds. This rapidity of action depends on its dose, dosage forms, and extent of chewing the tablets. The antacid efficacy of tested antacid was not affected by the concomitant presence of two tablets of duspatalin, faverin and panadol (group I) or their equivalent weights of pure powders, whilst, the duration of action, buffering capacity and total acid consumption was significantly suppressed with two dosage units of inderal, aspirin, and indocid (group II) or their equivalents of pure powder. However, antacid tested was still regulating gastric acid level within the comfort zone for a period of 70-110 min, and possessing (20.01-25.10 mEq/g) with group (II). These results are consistent with that obtained from acid neutralizing capacity test. The dissolution of magaldrate was pH dependent, with fast magnesium release and sustained aluminum hydroxide conversion. A significant (p < 0.05) retardation of the release rates of group (II), whilst, a non significant (p > 0.05) effect on that of group (I) was observed in the presence of different doses of antacid tested in all dissolution media. The presence of riopan suspension (20 ml) had a significant suppression on the release rates in all systems.