|Ask the Expert
My patients who travel to Mexico or Africa often ask whether they should take antibiotics to prevent traveler's
diarrhea. What should I advise them?
Sherwood Gorbach, MD
Departments of Community Health & Medicine, Tufts University School of Medicine, Boston, Massachusetts, USA
Travel to an area defined as high risk for diarrhea, which includes Mexico and Africa, as well as other parts of
Latin America and Asia, incurs a diarrhea risk of about 30-50% for persons from North America or Europe during
a 1-2 week journey. Several studies have shown that prophylactic antimicrobial drugs, taken continuously during
a trip, provide about 90% protection from diarrhea. The most successful drugs in this regard are trimethoprim-sulfamethoxazole
(TMP-SMX), tetracycline, and one of the quinolones (ciprofloxacin, ofloxacin, pefloxacin or norfloxacin). The alternative
approach to reducing the indignities of travel for those with reduced intestinal fortitude is education about how
to lower the risk of diarrhea and instructions on empiric self-treatment; these methods were favored over universal
prophylactic antibiotics by a NIH Consensus Conference convened in 1986 on this topic.
In the first instance the arguments against universal antimicrobial prophylaxis for travelerís diarrhea
(TD) should be considered in light of the epidemiology and clinical features. Another way to express the incidence
figures of TD is to state that 50-70% of travelers do not develop diarrhea. Among those who do develop TD, about
one half have mild symptoms, defined as 1 or 2 loose stools per 24 hours and only one accompanying symptom (e.g.,
cramps, nausea, etc.). In a study of US travelers to Mexico, 60% of persons with mild TD improved spontaneously
by the next day, without any treatment. Thus, TD which lasts more than one day occurs in only 10% of travelers,
although prophylaxis would require all travelers to take the antimicrobial drug. Side effects from continuous antimicrobial
prophylaxis is another concern, especially among healthy persons who are on vacation. While the figures are not
readily available, it appears that 3-5% of persons taking prophylactic antimicrobial drugs for TD develop some
untoward reaction. Skin rash, for example, has been reported in 2% of travelers taking norfloxacin for prophylaxis
and between 2 to 14% of persons taking TMP-SMX in various prophylaxis trials.
An alternative to prophylaxis is self-administered treatment once TD has occurred. Several anti-diarrheal drugs
have been used to treat mild to moderate TD, including bismuth subsalicylate (PeptoBismol) and the antimotility
agents (loperamide, diphenoxylate, codeine, tincture of opiate and paragoric), with complete relief usually within
24 hours. Among the latter class, loperamide is preferred because it has fewer central nervous system side effects.
Antimicrobial drugs such as TMP-SMX or a quinolone have been proven effective in treating severe TD (4 or more
loose stools in 24 hours). Combining loperamide with an antimicrobial drug has led to rapid resolution of symptoms
of moderate or severe TD, with significant improvement within one hour in most persons.
To summarize, antimicrobial agents are not recommended for prevention of TD for the following reasons: 1) Rapid
and effective treatment is available which can curtail the symptoms of TD within the day of onset; 2) Universal
prophylaxis among the 15 million US travelers to Mexico each year, as an example, could have important effects
on increasing antimicrobial resistance among intestinal pathogens; 3) Side effects occur in 3-5% of healthy vacationers
when taking prophylactic antimicrobial drugs; and 4) A false sense of security can be assumed by travelers who
take prophylactic antimicrobials, with the potential consequence of not following precautions for preventing food-
and water-borne disease in areas of high risk. Antimicrobial prophylaxis might be considered for travelers to high
risk countries who have an underlying health problem which could increase the risk and/or severity of TD, such
as gastric hypochlorhydria due to medications or disease, immunodeficiency state, inflammatory bowel disease, and
insulin-dependent diabetes mellitis. In any case, chemoprophylaxis should not be used if the traveler spends more
than 3-4 weeks in the high risk area.
Proper dietary precautions are important not only to prevent TD, but also other food-borne and water-borne infections,
such as typhoid fever, hepatitis A, brucellosis, poliomyelitis, bovine tuberculosis and listeriosis. The dietary
rule "If you canít cook it, peel it, or boil it ó forget it" captures most of the relevant
guidelines. All travelers to developing countries should practice these sound prevention strategies. Despite the
best intentions, and the most careful precautions, some travelers will still get TD since they may eat in restaurants
in which good food handling is not being followed . In these circumstances self-administered treatment provides