The most effective treatment for isosporiasis is a combination of two drugs:
trimethoprim and sulfamethoxazole (TMP-SMX; Bactrim™, Septra®).
To treat isosporiasis, two double-strength TMP-SMX pills are taken twice
a day. An alternative is one double-strength pill three times a day. TMP-SMX
treatment is usually continued for two to four weeks.
Unfortunately, between 25% and 50% of HIV-positive people are allergic
to the sulfur in the SMX half of TMP-SMX. Two of the main symptoms seen
in people with allergic reactions to SMX are fever and rash. Very often,
the allergy can be so severe that people need to stop taking SMX.
For patients who cannot tolerate SMX, the drug pyrimethamine (Daraprim®),
combined with folinic acid, can be taken. This combination of drugs
is used for a month.
To help control the diarrhea, perhaps in combination with antibiotic
therapy, a number of anti-diarrheal drugs can be taken. This include:
octreotide (Sandostatin®), diphenoxylate (Lomotil®), loperamide
(Imodium®), paregoric, and Pepto-Bismol®. And because
diarrhea is the direct result of intestinal inflammation caused by the
infection, some non-steroidal anti-inflammatory drugs (NSAIDS) may be
helpful such as ibuprofen (e.g., Advil®). Another drug that
has been shown to greatly reduce diarrhea, due to its anti-inflammatory
activity, is thalidomide (Thalomid®). Women who take this drug
should avoid becoming pregnant; thalidomide can cause severe birth defects.
The most effective way to prevent isosporiasis is to avoid its sources
– mainly potentially contaminated foods or human feces. This is particularly
true for HIV-positive people with compromised immune systems raveling
to tropical and subtropical countries where water and food could be contaminated.
Drinking bottled water and making sure that food is cooked properly can
help reduce the risk of isosporiasis while raveling to tropical and subtropical
areas.
Drugs used to prevent isosporiasis (prophylaxis) are, for the most part,
the same as those used to prevent Pneumocystis carinii
pneumonia (PCP). Trimethoprim-Sulfamethoxazole
(TMP-SMX; Bactrim™, Septra®) is the most effective combination
of drugs used to prevent PCP and to treat isosporiasis. And because PCP
prophylaxis is generally started when a person's T-cell count
falls below 200, he or she should be well protected against Isospora
belli in the event he or she is exposed to this protozoan.
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