For gastrointestinal infections caused by Enterocytozoon bieneusi, fumagillin 20 mg orally three times daily is the only drug with proven efficacy. However, its use is associated with severe thrombocytopenia in 30-50% of patients, which is reversible upon discontinuation of treatment, and the drug is not currently available in the United States.

For disseminated (not ocular) and intestinal infection attributed to microsporidia other than E. bieneusi and Vittaforma corneae, the drug of choice is albendazole 400 mg orally twice daily. Treatment should continue until immune reconstitution has been maintained for at least 6 months. Itraconazole 400 mg orally daily plus albendazole 400 mg orally twice daily may have activity for disseminated disease attributed to Trachipleistophora or Anncaliia.

For ocular infection, the treatment of choice is topical fumagillin bicylohexylammonium (Fumidil B) 3 mg/mL in saline (fumagillin 70 µg/mL) eye drops: two drops every 2 hours for 4 days, then two drops four times daily (investigational use only in United States) plus albendazole 400 mg orally twice daily for management of systemic infection.

Initiation or optimization of antiretroviral therapy is the cornerstone of treatment of microsporidiosis in HIV-infected patients. Immune restoration to CD4 cell count >100 cells/mm3 is associated with resolution of symptoms of enteric microsporidiosis. Management of severe dehydration, malnutrition, and wasting with fluid support and nutritional supplementation should be provided. Use of antimotility agents for diarrhea control can be considered in infected adults.

Although albendazole is likely less effective against E. bieneusi, there are reports of success with albendazole therapy in immunosuppressed patients.

For more information, please visit http://aidsinfo.nih.gov/guidelines.

* This drug is approved by the FDA, but considered investigational for this purpose.