Toxoplasmosis Organism-Specific Therapy 

Updated: Nov 16, 2015
  • Author: Darvin Scott Smith, MD, MSc, DTM&H; Chief Editor: Thomas E Herchline, MD  more...
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Therapeutic Regimens

Toxoplasmosis is caused by the protozoan Toxoplasma gondii, typically when tissue cysts in undercooked meat or oocysts shed in cat feces are ingested. In the vast majority of individuals, infection is asymptomatic, as a competent immune system is sufficient to keep the organism in a latent tissue cyst state. However, if these cysts reactivate, encephalitis may occur. Rarely, primary infection is associated with acute cerebral or disseminated disease. Immunocompromised or pregnant individuals are at highest risk when infected. In immunocompetent/nonpregnant individuals, only supportive therapy is necessary unless severe symptoms persist. All treatments should be administered orally unless otherwise indicated.

Immunocompromised patients (HIV/AIDS or transplantation)  [1, 2]

Initial treatment: Continue for 6 weeks after resolution of symptoms and imaging results

  • Pyrimethamine 200 mg loading dose, followed by weight-based therapy (50 mg/day for < 60 kg, 75 mg/day for >60 kg) plus  sulfadiazine 15 mg/kg, 4 times daily plus leucovorin (folinic acid) 10-20 mg/day

  • For those who are sulfadiazine hypersensitive, clindamycin 300 mg 4 times daily or atovaquone 1500 mg twice daily (with food) are acceptable substitutions

Consider IV steroid therapy for the treatment of mass effect attributed to focal lesions or associated edema. Anticonvulsants should be administered to patients with a history of seizures and continued through the acute treatment (but not given without a history of seizures).

Maintenance: Lifelong or until there is immune recovery (CD4 >200 cells/uL for more than 6 months)

  • Trimethoprim-sulfamethoxazole 480-960 mg/day or

  • For those who are intolerant to sulfa, dapsone 50 mg/day plus  pyrimethamine 50 mg/week plus  folinic acid 25 mg/week or

  • Atovaquone 1500 mg PO q24h alone or  with pyrimethamine 25 mg plus folinic acid 10 mg PO q24h

Congenital toxoplasmosis  [3]

Maternal infection 3 months before conception or during pregnancy, before 18 weeks of gestation, or immunocompromised women suspected of having reactivated latent Toxoplasma infection:

  • Spiramycin: 1 g q8h with food

Maternal infection after 18 weeks of infection:

  • Pyrimethamine 50 mg q12h for 2 days followed by 50 mg/day

  • Sulfadiazine loading of 75 mg/kg followed by 50 mg/kg q12h

  • Folinic acid 10-20 mg/day until 1 week following cessation of pyrimethamine treatment

Congenital infection of the newborn:

  • Pyrimethamine 1 mg/kg q12h for 2 days, followed by 1 mg/kg/day for 6 months, followed by 1 mg/kg 3 times a week

  • Sulfadiazine 50 mg/kg q12h

  • Folinic acid 10 mg 3 times a week until 1 week after cessation of pyrimethamine treatment

  • Treatment duration: 1 year