eMedicine Specialties > Pediatrics: General Medicine > Parasitology
Isosporiasis: Treatment & Medication
Updated: Jan 22, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Treatment
Medical Care
Although generally a self-limited infection, patients with isosporiasis who are treated tend to improve in 2-3 days, whereas those who are not treated remain sick considerably longer. Immunocompetent hosts generally respond very rapidly to antiparasitic therapy, with symptomatic improvement within 5 days. The immunocompromised host also responds well, although less rapidly. However, these individuals relapse at a high rate (50% in 2 mo) once therapy is stopped. Thus, indefinite prophylaxis following therapy is recommended in this population. Therapy for dehydration may be the most urgent intervention required.
Consultations
Consultation with an infectious diseases specialist, a gastroenterologist, or both may be appropriate.
Diet
A standard diarrhea diet may be appropriate, until symptoms resolve.
Medication
Unlike many of the protozoal infections that cause similar diseases, effective therapies are available for isosporiasis.
Antiprotozoal agents
Trimethoprim-sulfamethoxazole (TMP-SMZ) is the drug of choice because it is the best-studied and most readily available agent. Many patients with AIDS are already taking this agent as prophylaxis for Pneumocystis infection. An alternative for long-term prophylaxis is pyrimethamine with sulfadiazine or sulfadoxine (either of which should be accompanied by folinic acid). For patients who cannot tolerate sulfonamides, ciprofloxacin or pyrimethamine plus folinic acid may be nearly as effective for both acute treatment and prophylaxis.
The US Food and Drug Administration considers all of these regimens investigational for this infection. Studies have proposed the veterinary agent diclazuril as a possible drug of choice if further studies confirm its use and safety.3 Doxycycline, roxithromycin, and nitazoxanide4,5 are reported to have some efficacy, but only a few of these reports are available; thus, recommending these drugs is premature at present.
Sulfamethoxazole and trimethoprim (Bactrim, Septra, Cotrim)
Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid. DOC and curative in the immunocompetent host. Can be used for treatment and then ongoing prophylaxis in the immunocompromised host.
Adult
160 mg TMP/800 mg SMZ PO qid (ie, 1 double-strength [DS] tab qid) for 10 d; then bid for 21 d (2 wk may suffice in immunocompetent patient)
Posttreatment prophylaxis: 160 mg TMP/800 mg SMZ PO qd (3 times/wk may also suffice)
Pediatric
<2 months: Contraindicated
>2 months:
5 mg/kg (based on TMP component) PO tid for 10 d; then bid for 2 wk; not to exceed 160 mg TMP/800 mg SMZ (ie, 1 DS tab) per dose
Posttreatment prophylaxis: 5 mg/kg (based on TMP component) PO qd (3 times/wk may also suffice); not to exceed 1 DS tab/d
May increase PT when used with warfarin (perform coagulation tests and adjust dose accordingly); coadministration with dapsone may increase blood levels of both drugs; coadministration of diuretics increases prevalence of thrombocytopenia purpura in elderly patients; phenytoin levels may increase with coadministration; may potentiate effects of methotrexate in bone marrow depression; hypoglycemic response to sulfonylureas may increase with coadministration; may increase levels of zidovudine
Documented hypersensitivity; megaloblastic anemia due to folate deficiency; age <2 mo
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Do not use near term in pregnancy because of possible kernicterus in newborns; possible blood dyscrasias, crystalluria, glossitis, renal or hepatic injury, gastrointestinal irritation, rash, Stevens-Johnson syndrome, and hemolysis with G-6-PD deficiency; reduce dose in renal impairment
Pyrimethamine (Daraprim)
The second DOC and particularly useful for those who cannot tolerate sulfonamides. It can also be used for prophylaxis, when combined with sulfadiazine or sulfadoxine. Administer with folinic acid to prevent hematologic toxicities.
Adult
75 mg PO qd for 21 d
Posttreatment prophylaxis: 25 mg PO qd
Pediatric
Not established
Concurrent use of antifolate medications (eg, methotrexate, pyrimethamine) may increase risk of bone marrow suppression, discontinue pyrimethamine therapy if signs of folate deficiency develop; coadministration with lorazepam may cause mild hepatotoxicity
Documented hypersensitivity; megaloblastic anemia resulting from a folate deficiency
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
If signs of folate deficiency develop, reduce dose or discontinue drug, depending on patient response; caution in hepatic or renal impairment; monitor for toxoplasmosis by performing semiweekly blood counts, including platelet counts; may precipitate hemolytic anemia in G-6-PD deficiency, generally in the presence of other stressful events
Sulfadoxine and pyrimethamine (Fansidar)
Acts by reciprocal potentiation of its 2 components, achieved by a sequential blockade of 2 enzymes involved in the biosynthesis of folinic acid within the parasites. In patients not allergic to sulfonamides, can be an alternative to TMP-SMZ for long-term prophylaxis. Administer with folinic acid to prevent hematologic toxicities. Contains sulfadiazine 500 mg and pyrimethamine 25 mg per tab.
Adult
500 mg sulfadiazine/25 mg pyrimethamine PO qwk
Pediatric
Not established
Sulfadoxine component is highly protein bound and may displace warfarin that is protein bound, thus increasing INR; coadministration with other folic acid antagonists (eg, methotrexate, TMP-SMZ, dapsone) increases potential for hematologic toxicities
Documented hypersensitivity; megaloblastic anemia resulting from a folate deficiency
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Do not use near term in pregnancy because of risk of kernicterus in newborn; caution in premature infants and infants <2 mo (risk of hyperbilirubinemia); caution in hepatic or renal dysfunction (30-44% eliminated in urine); maintain hydration; possible fever, rash, hepatitis, systemic lupus erythematosus–like syndrome, vasculitis, bone marrow suppression, and hemolysis with G-6-PD deficiency and Stevens-Johnson syndrome; for pyrimethamine component, possible glossitis, seizures, rash, and photosensitivity
Diclazuril (Clinacox)
Investigational in the United States. This benzene acetonitrile derivative is a veterinary antiparasitic that has shown good safety and efficacy in a small number of studies involving a small number of humans. Clinical trials have been completed for use in patients with AIDS and cryptosporidial-related diarrhea. May become the DOC if further studies confirm these preliminary findings.
Adult
300 mg PO bid
Pediatric
Not established
None reported
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Limited data available; none reported
Vitamins
Folinic acid is a required supplement if pyrimethamine is used.
Leucovorin (Wellcovorin)
Also called folinic acid. Reduced form of folic acid that does not require enzymatic reduction reaction for activation. Allows for purine and pyrimidine synthesis, both of which are needed for normal erythropoiesis. Important cofactor for enzymes used in production of RBCs. Daily supplementation is required if pyrimethamine therapy is used.
Adult
5-10 mg PO qd
Pediatric
Not established
Decreases effect of methotrexate, phenytoin, phenobarbital, and TMP-SMZ combinations; increases toxicity of fluorouracil
Documented hypersensitivity; pernicious anemia; vitamin-deficient megaloblastic anemias
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Resistance to treatment may occur in patients with alcoholism and deficiencies of other vitamins
More on Isosporiasis |
| Overview: Isosporiasis |
| Differential Diagnoses & Workup: Isosporiasis |
 Treatment & Medication: Isosporiasis |
| Follow-up: Isosporiasis |
| References |
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Further Reading
Keywords
isosporiasis, Apicomplexa coccidia protozoan, dehydration, diarrhea, foul-smelling flatus, gastrointestinal infection, GI infection, Isospora, Isospora belli, I belli, I belli disease, I belli infection, parasitic infection, steatorrhea
