TreatmentUpdate 65, Volume 8, No 1; January 1996
Sean Hosein
In North America, people with HIV/AIDS who have less than 100 CD4+ cells and who have been exposed to the parasite (T. gondii) are considered to be at high risk for developing toxo. In France and Germany, where toxo is more common, doctors may begin anti-toxo regimens when CD4+ cell counts fall below 150 cells.
People with toxo usually have a number of signs/symptoms which may include:
X-ray and magnetic scans will usually detect brain lesions and anti-toxo antibodies may be present in their blood samples.
Patients can receive two antibiotics: (a) between 100 and 200 mg pyrimethamine on the first day followed by lower doses between 50 and 75 mg/day for as many as eight weeks; (b) between 4 and 6 grams/day of sulphadiazine, also for up to 8 weeks. Some doctors may prescribe an artificial form of the B-vitamin folic acid (folate) called leucovorin between 10 and 20 mg/day. The doses of the three drugs may be altered depending on the state of health, and severity of infection and toxicity of the drugs. Pyrimethamine and sulphadiazine are considered the best combination therapy for toxo.
For patients allergic to sulpha drugs, doctors may prescribe a different antibiotic; in this case clindamycin between 1200 and 2400 mg/day may be taken together with pyrimethamine. Clindamycin can be taken by mouth or intravenously (iv).
There have been no large studies using azithromycin to treat toxo. In 2 cases, use of 1,200 mg/day of azithromycin did not prove effective.
In one study, doctors used pyrimethamine 75 mg/day and clarithromycin 2,000 mg/day together with leucovorin 20 mg/day in 13 subjects, 8 of whom completed 6 weeks of therapy. Although most subjects improved, the combination was not as effective as clindamycin and pyrimethamine. Side effects from use of high doses of clarithromycin included "nausea, vomiting, skin rash, [temporary] loss of hearing, liver and bone marrow damage." Neither clarithromycin nor azithromycin is adequate treatment when given alone.
Given Bactrim/Septra at a dose between 40 and 50 mg/kg of body weight per day, patients have recovered from toxo.
In one study, 93 subjects with toxo received Mepron 750 mg, three times daily with food. Most subjects who absorbed sufficient amounts of the drug improved or did not become worse.
In one experiment, subjects unable to tolerate standard therapy received trimethrexate between 30 and 120 mg per square metre of skin with leucovorin (20 to 90 mg/ m2 of skin). Although 5 subjects showed reduced signs/symptoms of toxo within the first 2 weeks of treatment, X-ray scans of their brains detected lesions that took up to 2 months to clear.
1. Behbahani R, Moshfeghi M and Baxter JD. Therapeutic approaches for AIDS-related toxoplasmosis. Annals of Pharmacotherapy 1995;29:760-768.
2. Albrecht H and Stellbrink H-J. Prophylaxis for opportunistic infections. Annals of Internal Medicine 1995;122(3):730-731.
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