Effects of aluminum and magnesium antacids and ranitidine on the absorption of ciprofloxacin

David E. Nix, William A. Watson, Michelle E. Lener, R. Wayne Frost, George Krol, Harvey Goldstein, John Lettieri, Jerome J. Schentag

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168 Scopus citations


The effect of an antacid (Maalox) and ranitidine administration on the absorption of ciprofloxacin was evaluated in healthy male volunteers who were enrolled in three separate studies. Each study was designed as a three- or four-period crossover and included the administration of 750 mg ciprofloxacin alone as a control treatment. Treatments that were evaluated included the administration of ciprofloxacin 5 to 10 minutes, 2 hours, 4 hours, and 6 hours after a single 30 ml dose of antacid; the administration of antacid 2 hours after ciprofloxacin was given; and the administration of ciprofloxacin 2 hours after a 200 mg ranitidine tablet. Administration of antacid within 4 hours before ciprofloxacin dose resulted in a significant decrease in ciprofloxacin absorption (p < 0.05). Percentages of relative bioavailability compared with control values were 15.1%, 23.2%, and 70% for the 5 to 10 minute, 2 hour, and 4 hour antacid pretreatments, respectively. Administration of antacid 6 hours before or 2 hours after the ciprofloxacin dose did not affect absorption. Ranitidine did not alter ciprofloxacin absorption. Antacids that contain magnesium and aluminum salts may reduce the absorption of ciprofloxacin. The extent of this interaction appears to increase as the time between administration of the two drugs decreases. Ranitidine is suggested as an alternative to antacids for patients receiving treatment with ciprofloxacin.

Original languageEnglish (US)
Pages (from-to)700-705
Number of pages6
JournalClinical Pharmacology and Therapeutics
Issue number6
StatePublished - Dec 1989

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)


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