The protozoan Toxoplasma gondii is an obligate intracellular parasite, one of the most common causes of intraocular inflammation in the world. Treatment of toxoplasmosis is made with the sulfonamide group of drugs, which act on the tachyzoite forms, preserving the bradyzoites, which is to multiply from latent foci, are responsible for tables of recurrence. Our study aims to determine the effect of prophylactic therapy with Trimethoprim-Sulfamethoxazole on recurrences of Toxoplasma gondii retinochoroiditis. This is a randomized, double-masked, in patients with ocular picture of acute Toxoplasma gondii retinochoroiditis. The study population consists of patients treated as outpatients of Ophthalmology, Universidade Estadual de Campinas, presenting symptoms compatible with a diagnosis of recurrent ocular toxoplasmosis. Volunteers will be included with a previous diagnosis of chorioretinitis presumed Toxoplasma gondii, which show active lesions compatible with recurrence. After treatment of the acute phase of all patients [one tablet of trimethoprim-sulfamethoxazole (800/160mg) 12/12h during 45 days] the same (stratified by gender) will be randomized in a 1:1 ratio between group 1 ( prophylactic treatment with one tablet of trimethoprim-sulfamethoxazole on alternate days) or group 2 (consisting of a placebo pill containing no active ingredient, using starch as an excipient, a look similar to trimethoprim-sulfamethoxazole, a once daily on alternate days). The definition adopted in a patient with recurrent episodes of toxoplasmosis chorioretinitis is the presence of old scars of chorioretinitis, satellite lesions associated with active chorioretinitis with positive IgG and IgM negative for toxoplasmosis. Study patients will be tested for visual acuity, biomicroscopic examination, tonometry, ophthalmoscopy and indirect ophthalmoscopy. In each study, patients will be randomized in blocks of four (two in group I and two group II) with stratification by gender. The primary outcome is incidence of episodes of recurrent toxoplasmosis chorioretinitis during the follow up of 12 months. It was planned a minimum sample of 140 patients (70 in group I and 70 in group II). Assuming an incidence of 6% recurrence in group I, this sample will have a 80% power to detect a difference of 18% among groups. The results of this analysis will be considered significant if p <0.05.
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