Antacids

Snapshot

A 30-year-old lawyer presents to her primary care physician for the evaluation of nonbloody diarrhea. She reports that she has around 2 episodes a day and that her stool consistency is very watery. As her physician asks about any travel or food exposures, she takes out a pill and pops one in her mouth. When asked about this, she reports, “I have been under so much stress lately and these antacids are helping with my abdominal pain.” On closer exam, these pills are magnesium hydroxide. She is counseled about the side effects of osmotic diarrhea.

Introduction

Antacids
	Aluminum Hydroxide	Calcium Carbonate	Magnesium Hydroxide
Mechanism of action	Neutralizes acid in the stomachDelays gastric emptying
Also acts as a phosphate binder	Promotes osmotic retention of fluid and induces diarrhea
Clinical use	Acid refluxPeptic ulcer diseaseAluminum hydroxide
	Hyperphosphatemia	Calcium supplementation	Constipation
Adverse effects	ConstipationDecreased phosphatemuscle weaknessosteodystrophy	Milk-alkali syndrome↑ calciumin severe cases, can cause metastatic calcification and renal failureCan chelate and decrease the efficacy of some drugs, particularly tetracyclines (doxycycline, tetracycline, and minocycline)	DiarrheaHypotensionCardiac arrest