Nonantimicrobial Drugs for Prophylaxis
The primary agent studied for prevention of TD, other than
antimicrobial drugs, is bismuth subsalicylate (BSS), which is the
active ingredient in Pepto-Bismol. Studies from Mexico have shown
this agent (taken daily as either 2 oz of liquid or two chewable
tablets four times per day) reduces the incidence of TD from 40% to
14%. BSS commonly causes blackening of the tongue and stool and may
cause nausea, constipation, and rarely tinnitus. BSS should be
avoided by travelers with aspirin allergy, renal insufficiency, and
gout, and by those taking anticoagulants, probenecid, or
methotrexate. In travelers taking aspirin or salicylates for other
reasons, the use of BSS may result in salicylate toxicity. Caution
should be used in administering BSS to children with viral
infections, such as varicella or influenza, because of the risk for
Reye syndrome. BSS is not recommended for children <3 years of age.
Studies have not established the safety of BSS use for periods >3
weeks.
The use of probiotics, such as Lactobacillus GG and
Saccharomyces boulardii, has been studied in the prevention of
TD in limited numbers of subjects. Results are inconclusive,
partially because standardized preparations of these bacteria are
not reliably available.
Oral Rehydration Therapy
Fluids and electrolytes are lost in cases of TD, and replenishment
is important, especially in young children or adults with chronic
medical illness. In adult travelers who are otherwise healthy,
severe dehydration resulting from TD is unusual unless prolonged
vomiting is present. Nonetheless, replacement of fluid losses
remains an important adjunct to other therapy and helps the traveler
feel better more quickly. Travelers should remember to use only
beverages that are sealed or carbonated, or otherwise known to be
purified. For more severe fluid loss, replacement is best
accomplished with oral rehydration solutions (ORS), such as the WHO
ORS solutions, which are widely available at stores and pharmacies
in most developing countries (see Table 2-25 for details). ORS is
prepared by adding one packet to the appropriate volume of boiled or
treated water. Travelers may find most ORS formulations to be
relatively unpalatable, due to their saltiness. In most cases,
rehydration can be maintained with any palatable liquid.
Table 2-25. Composition of WHO oral rehydration salts (ORS) for
diarrheal illness
| Ingredient |
Amount |
| Sodium chloride |
2.6 g/L |
| Potassium chloride |
1.5 g/L |
| Glucose, anhydrous |
13.5 g/L |
| Trisodium citrate,
dihydrate |
2.9 g/L (or 2.5 g/L) |
| Water |
1.0 L |
1World Health Organization. Oral
Rehydration Salts (ORS): Production of the new ORS. Geneva: WHO;
2006: p. 2–4.