Over-the-Counter Antacids

Kreidler, Kathy                          Thornridge High School
1765 State Street, Apt. 6                      841-5180
Calumet City, IL  60409
862-0765

Objectives:  

Over one-half billion dollars are spent on over-the-counter antacids 
every year.  An informed consumer will understand how antacids work and 
will read the labels to see what ingredients are present. Based on this 
information and on a knowledge of side effects, the student consumer 
will be able to decide which, if any, antacid to choose. 

Apparatus needed:

6 250 ml Erlenmeyer flasks             baking soda
6 balloons                             Tums
600 ml 0.1 M hydrochloric acid         Rolaids
Alka Seltzer                           Phillips Milk of Magnesia
Maalox tablets                         methyl orange indicator

Recommended strategy:

Before class starts, prepare 6 little stomachs. These are 250 ml 
Erlenmeyer flasks, each containing 100 ml of 0.1 M HCl and a few drops 
of methyl orange indicator.  Put an empty balloon over the mouth of the 
control flask.  Crush one dose of each antacid and place in a balloon. 
Label the bottom of each flask to correspond to the antacid in the 
balloon. Place the balloons over the necks of the flasks, but do not 
allow the antacids to fall into the flasks yet. 

Tell the students that you have an upset stomach from eating too much 
pizza last night.  Ask what you could take to get relief from 
indigestion and "sour stomach."  Place samples of antacids on the desk.  
Explain the little stomachs setup.  Shake the balloons so the antacids 
fall into the flasks.  Record student observations and explanations on 
the chalkboard. 

Pass out a list of ingredients of common antacids.  The list could also 
include the price per dose. Ask what ingredients could neutralize acid 
and what ingredients could relieve gas pains. 

Teacher input:
Write representative neutralization equations.  Explain the action of 
simethicone.  Tell some of the side effects of aspirin, magnesium, 
aluminum, and sodium salts.  Discuss the function of the inactive 
ingredients.  Ask the students to use this new information and their 
observations to guess which antacid was in each flask. 

Evaluation:
Students work in groups to decide which antacid is the best.  Each 
group shares its decision and the criteria used to arrive at that 
decision. 



References:
Eby, Denise and Roger Tatum. The Chemistry of Over-the-Counter Drugs.  
Unigraph:  Seattle, Washington, 1977.  pp.14-21.

Graedon, Joe.  The People's Pharmacy.  St. Martin's Press:  New York, 
1976.  pp.79-90.

Rombauer, Irma S. and Marion Rombauer Becker.  The Joy of Cooking.  
Bobbs, Merrill:  Indianapolis, 1962.  p. 557. 

Strongin, Herb.  Science on a Shoestring.  Addison Wesley:  Menlo 
Park, California, 1985.  pp. 41-43.