What is the first line of treatment for toxoplasmosis?

First-Line Treatment for Toxoplasmosis

The first-line treatment for toxoplasmosis is pyrimethamine combined with sulfadiazine, plus leucovorin (folinic acid) supplementation. 1, 2

Treatment Regimens Based on Patient Population

For Congenital Toxoplasmosis

• Pyrimethamine: Loading dose of 2 mg/kg/day for 2 days, then 1 mg/kg/day for 2-6 months, followed by 1 mg/kg three times weekly 1
• Sulfadiazine: 50 mg/kg twice daily 1
• Leucovorin (folinic acid): To minimize pyrimethamine-associated hematologic toxicity 1
• Duration: 12 months of treatment 1

For Acquired Toxoplasmosis in HIV-Infected Individuals

• Pyrimethamine: 2 mg/kg/day for 3 days, followed by 1 mg/kg/day 1
• Sulfadiazine: 25-50 mg/kg four times daily 1
• Leucovorin: 10-25 mg/day 1
• Duration: Acute therapy for 6 weeks, assuming clinical and radiological improvement 1

For Pregnant Women with Toxoplasmosis

Treatment approach varies based on gestational age and fetal infection status:

1. Before 16 weeks of pregnancy:

   • Spiramycin: Used until 16th week of pregnancy 1
   • Note: Spiramycin is not commercially available in the US but can be obtained through the FDA at no cost 1

2. After 16 weeks or confirmed fetal infection:

   • Switch to pyrimethamine/sulfadiazine plus folinic acid 1

Monitoring During Treatment

• Complete blood count: Weekly while on daily pyrimethamine and at least monthly while on less frequent dosing 1
• Monitor for adverse effects:
  • Pyrimethamine: Bone marrow suppression (neutropenia, anemia, thrombocytopenia), rash, nausea 1, 2
  • Sulfadiazine: Rash, fever, leukopenia, hepatitis, GI symptoms, crystalluria 1

Alternative Regimens for Sulfa-Allergic Patients

• Clindamycin (5.0-7.5 mg/kg orally 4 times daily; maximum 600 mg/dose) with pyrimethamine and leucovorin 1
• Azithromycin (900-1,200 mg/day) with pyrimethamine and leucovorin has been used in adults but is less studied in children 1

Important Considerations and Precautions

• Leucovorin must always be administered with pyrimethamine to prevent bone marrow toxicity 1, 2
• Continue leucovorin for 1 week after pyrimethamine discontinuation due to the long half-life of pyrimethamine 1
• Pyrimethamine is contraindicated in the first trimester of pregnancy due to teratogenic effects 2
• Pyrimethamine should be used with caution in patients with seizure disorders, impaired renal or hepatic function 2
• Keep pyrimethamine out of reach of children as they are extremely susceptible to adverse effects from overdose 2

Treatment Efficacy

The German approach of using spiramycin until 16 weeks of pregnancy followed by at least 4 weeks of combination therapy with pyrimethamine, sulfadiazine, and folinic acid has shown very low rates of mother-to-child transmission (4.8%) compared to other European cohort studies (30%) 1, 3.

This treatment protocol prioritizes early intervention to reduce both transmission rates and severity of disease in infected infants, which directly impacts morbidity, mortality, and quality of life outcomes.