Question 5 - Opportunistic Infections: Treatment Question Bank

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Opportunistic Infections: TreatmentQuestion 5/20

A 40-year-old man with HIV is seen in the emergency room after he suffered a generalized tonic-clonic seizure. He has not been engaged in care and is not taking any medication. The last known CD4 count was 22 cells/mm³. The serum anti-Toxoplasma IgG test was positive when he entered care 3 years prior. Magnetic resonance imaging (MRI) of the brain demonstrates multiple ring-enhancing intracranial lesions with vasogenic edema and mass effect, the largest being in the right frontal-parietal lobe (Figure 1). A diagnosis of Toxoplasma encephalitis is strongly suspected. The pharmacy informs you that first-line therapy with pyrimethamine plus sulfadiazine is not an option due to the inability to get pyrimethamine. He does not have any medication allergies.

In this patient, which one of the following should be recommended for treatment of probable Toxoplasma encephalitis?

Atovaquone plus primaquine

Trimethoprim plus dapsone

Treimethoprim-sulfamethoxazole

Clarithromycin plus clindamycin

Figure 1. Brain Magnetic Resonance Imaging in Patient with Toxoplasma Encephalitis.

The image on left shows multiple ring-enhancing lesions. The image on the right shows a large ring-enhancing lesion with surrounding edema and mass effect.

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Question Last Updated
April 30th, 2026

Table 1. Initial Therapy for Toxoplasma gondii Encephalitis

Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV

Recommendations for Treating Acute *Toxoplasma gondii* Encephalitis
Preferred Regimens for Acute Infection Pyrimethamine 200 mg PO once, followed by weight-based dosing (AI): Body weight ≤60 kg: pyrimethamine 50 mg PO daily plus sulfadiazine 1,000 mg PO every 6 hours plus leucovorin 10–25 mg PO daily (can increase to 50 mg daily or twice daily) Body weight >60 kg: pyrimethamine 75 mg PO daily plus sulfadiazine 1,500 mg PO every 6 hours plus leucovorin 10–25 mg PO daily (can increase to 50 mg daily or twice daily) or Trimethoprim-Sulfamethoxazole (trimethoprim 5 mg/kg and sulfamethoxazole 25 mg/kg) (IV or PO) twice daily (AII) Note: if pyrimethamine is unavailable or cannot be obtained without delay due to cost or other factors, trimethoprim-sulfamethoxazole should be used in place of pyrimethamine plus sulfadiazine (AII).
Alternative Regimens for Acute Infection (Pyrimethamine plus leucovorin)^a plus clindamycin 600 mg IV or PO every 6 hours (AI); preferred alternative for patients intolerant of sulfadiazine or who do not respond to pyrimethamine-sulfadiazine; must add additional agent for PCP prophylaxis (AII), or Atovaquone^b 1,500 mg PO twice daily plus (pyrimethamine + leucovorin)^a (BII), or Atovaquone^b 1,500 mg PO twice daily plus sulfadiazine^c (BII), or Atovaquone^b 1,500 mg PO twice daily (BII) For patients with a history of sulfa allergy, rapid sulfa desensitization may be attempted using one of several published strategies (BI). During the desensitization phase, atovaquone 1,500 mg PO should be administered twice daily until therapeutic doses of trimethoprim-sulfamethoxazole (trimethoprim 5 mg/kg and sulfamethoxazole 25 mg/kg) twice daily are achieved (CIII).
Total Duration for Treating Acute Infection At least 6 weeks (BII); longer duration if clinical or radiologic disease is extensive or response is incomplete at 6 weeks After completion of the acute therapy, all patients should be continued on chronic maintenance therapy.
Other Considerations Adjunctive corticosteroids (e.g., dexamethasone) should only be administered when clinically indicated to treat a mass effect associated with focal lesions or associated edema (BIII) or for control of clinically significant immune reconstitution inflammatory syndrome (IRIS) symptoms in conjunction with antiretroviral therapy and anti-toxoplasma therapy (CIII); discontinue as soon as clinically feasible. For patients in whom the diagnosis of toxoplasma encephalitis is presumptive based in part on clinical response, one needs to be careful as central nervous system lymphoma may also respond to steroids clinically and radiologically. Antiseizure medications should be administered to patients with toxoplasma encephalitis and associated seizures (AII) and continued through at least the period of acute treatment (BII); antiseizure medications should not be used as prophylaxis in patients without seizures (BII).
^a Pyrimethamine and leucovorin doses: Same as doses listed in Preferred Regimens for Acute Infection ^b Atovaquone should be taken with meals or nutritional supplements to ensure adequate oral absorption. ^c Sulfadiazine dose: Same as weight-based dose and frequency listed in Preferred Regimen for Acute Infection Abbreviations: PO = orally; IV = intravenous; PCP = Pneumocystis pneumonia Rating System for Prevention and Treatment Recommendations Strength of Recommendation: A = Strong; B = Moderate; C = Weak Quality of Evidence for the Recommendation: I = One or more randomized trials with clinical outcomes and/or validated laboratory endpoints; II = One or more well-designed, non-randomized trials or observational cohort studies with long-term clinical outcomes; III = Expert opinion

Source:

Panel on Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV. Guidelines for the prevention and treatment of opportunistic infections in adults and adolescents with HIV. National Institutes of Health, HIV Medicine Association, and Infectious Diseases Society of America. Toxoplasmosis. Updated: September 9, 2025. [HIV.gov]

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