Short - term Results of Two Treatment Regimens in Ocular Toxoplasmosis: Trimethoprim / Sulfamethoxazole versus Pyrimethamine and Sulfadiazine

To compare the efficacy of classic treatment for ocular toxoplasmosis (pyrimethamine, sulfadiazine and predinsolone) with a regimen consisting of trimethoprim/sulfamethoxazole (TMP/SMX) [co-trimoxazole] plus predinsolone.

In a prospective randomized single-blind clinical trial, 59 patients with active ocular toxoplasmosis were randomly assigned to two treatment groups: 29 were treated with pyrimethamine/sulfadiazine and 30 patients received TMP/SMX. Treatment consisted of six weeks treatment with antibiotics plus steroids. Anti-toxoplasmosis antibodies (IgM and IgG) were measured using ELISA. Outcome measures included changes in retinochoroidal lesion size after six weeks of treatment, visual acuity before and after intervention, adverse drug reactions during follow up and rate of recurrence.

Active toxoplasmosis retinochoroiditis resolved in all patients over six weeks of treatment with no significant difference in mean reduction in retinochoroidal lesion size between the two treatment groups (61% reduction in the classic treatment group and 59% in the TMP/SMX group, P=0.75). Similarly no significant difference was found in visual acuity after treatment between the two groups [mean visual acuity after treatment was 0.12 LogMAR (20/25) in classic treatment group and 0.09 LogMAR (20/25) in TMP/SMX group, P = 0.56]. Adverse events were similar in both groups with one patient in each suffering from any significant drug side effects. The overall recurrence rate after 14 months of follow up was 6.7% with no significant difference between the treatment groups (P = 0.48).

Drug efficacy in terms of reduction in retinal lesion size and improvement in visual acuity was similar between a regimen of TMP/SMX and the classic treatment of ocular toxoplasmosis with pyrimethamine and sulfadiazine. Therapy with TMP/SMX appears to be an acceptable alternative for the treatment of ocular toxoplasmosis.