Toxoplasmosis Organism-Specific Therapy 

Updated: Jun 02, 2020
  • 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. [1] 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. [2, 3]

Immunocompetent  patients ( not pregnant)  [4]

Treatment is usually unnecessary because most immunocompetent nonpregnant patients experience mild self-limited symptoms.

Treatment should be considered for a total of 4-6 weeks in patients with severe or persistent symptoms, ocular involvement, or laboratory-acquired infection using the following regimens:

  • Pyrimethamine 100-mg loading dose followed by 25-50 mg/day plus  sulfadiazine 1 g q6h plus  folinic acid 10-20 mg/day or
  • Trimethoprim-sulfamethoxazole 5 mg/25 mg to 10 mg/50 mg/kg/day in divided doses

Options in patients who are sulfadiazine-hypersensitive include the following:

  • Pyrimethamine 100-mg loading dose followed by 25-50 mg/day plus  folinic acid 10-20 mg/day plus
  • Clindamycin 300 mg q6h or
  • Azithromycin 250-500 mg daily or
  • Atovaquone 750-1500 mg twice daily (with food)

In patients with active chorioretinitis, higher doses may be needed, in addition to concomitant steroid therapy (prednisone 0.5-1 mg/kg/day with gradual tapering), as follows:

  • Pyrimethamine 200-mg loading dose followed by weight-based therapy (50 mg/day for < 60 kg, 75 mg/day for >60 kg) plus  weight-based sulfadiazine (1 g q6h for < 60 kg, 1.5 g q6h for >60 kg) plus folinic acid 10-50 mg/day

Immunocompromised patients (patients with HIV/AIDS or transplant recipients)  [5, 6, 4]

Initial treatment in immunocompromised patients is 6 weeks until resolution of symptoms and imaging followed by maintenance therapy, as follows:

  • Pyrimethamine 200-mg loading dose followed by weight-based therapy (50 mg/day for < 60 kg, 75 mg/day for >60 kg) plus  weight-based sulfadiazine (1 g q6h for < 60 kg, 1.5 g q6h for >60 kg) plus  folinic acid 10-50 mg/day or
  • Trimethoprim-sulfamethoxazole 10 mg/50 mg/kg/day in divided doses

Options in patients who are sulfadiazine-hypersensitive are as follows:

  • Pyrimethamine 200-mg loading dose, followed by weight-based therapy (50 mg/day for < 60 kg, 75 mg/day for >60 kg) plus  folinic acid 10-50 mg/day plus
  • Clindamycin 600 mg q6h or
  • Atovaquone 1500 mg twice daily (with food)

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 period (but not given without a history of seizures).

Maintenance therapy is lifelong or until there is immune recovery (in the setting of HIV, CD4 >200 cells/uL >6 months)

  • Pyrimethamine weight-based therapy (25 mg/day for < 60 kg, 50 mg/day for >60 kg) plus  weight-based sulfadiazine (0.5 g q6h for < 60 kg, 1 g q6h for >60 kg) plus  folinic acid 10-25 mg/day or
  • TMP-SMX (5 mg/25 mg/kg/day in divided doses)

Options in patients who are sulfadiazine-hypersensitive are as follows:

  • Pyrimethamine weight-based therapy (25 mg/day for < 60 kg, 50 mg/day for >60 kg) plus  folinic acid 10-25 mg/day plus
  • Clindamycin 600 mg q8h or
  • Atovaquone 750-1500 mg twice daily (with food)

Primary prophylaxis to prevent infection is as follows:

  • 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

Pregnant women with toxoplasmosis  [7]

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

  • Spiramycin: 1 g q8h with food until delivery

Maternal infection after 18 weeks of infection:

  • Pyrimethamine 50 mg q12h for 2 days followed by 50 mg/day plus  weight-based sulfadiazine loading dose of 75 mg/kg followed by 50 mg/kg q12h plus folinic acid 10-20 mg/day until 1 week following cessation of pyrimethamine treatment

Congenital toxoplasmosis:

  • 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 plus
  • Sulfadiazine 50 mg/kg q12h plus
  • Folinic acid 10 mg 3 times a week until 1 week after cessation of pyrimethamine treatment
  • Treatment duration: At least 1 year