Antacids + Azithromycin = Unknown or no reaction

Effect on Concentration

Antacids
Unknown
Applies within class?
No
Azithromycin
Decrease
Applies within class?
No

Pharmacologic Effects

Antacids
Effect
N/A
Applies within class?
No
Azithromycin
Effect
N/A
Applies within class?
No

Interaction History

N/A

Last Updated 22-May-2020

Summary

Peak concentrations were slightly reduced, however, extent of full absorption was not affected.

Sources

The Effects of an Antacid or Cimetidine on the Serum Concentrations of Azithromycin ^

Study Design

The effects of an antacid and of cimetidine on the serum concentrations of azithromycin were examined in volunteers. Ten subjects were given 500 mg azithromycin alone and immediately after being given 30 mL Maalox (Rorer, Fort Washington, PA) in a crossover design. Two groups of six volunteers were given 500 mg azithromycin on day 1. On day 8, one group was given 800 mg cimetidine 2 hours before a dose of azithromycin; the remaining group received placebo before azithromycin.

Study Results

There were no statistically significant differences in Tmax or AUC0-48 after administration of azithromycin alone or with antacid, but mean values of Cmax were reduced by 24 (P .015). Thus, although Cmax was decreased, the extent of absorption of azithromycin was not affected by coadministration with an antacid. There were no differences in the pharmacokinetic parameters produced by administration with cimetidine or placebo, relative to those on day 1.

Study Conclusions

Thus, cimetidine administered 2 hours before a dose of azithromycin had no apparent effect on the serum concentrations of azithromycin.

References

Foulds G. The effects of an antacid or cimetidine on the serum concentrations of azithromycin. J Clin Pharmacol. 1991; 2: 164-7.