Sulfonamide Allergy and Alternative Treatments in Ocular Toxoplasmosis

Abstract

Purpose: To summarize current knowledge on the clinical features, diagnosis, and treatment of ocular toxoplasmosis, with emphasis on alternatives for sulfonamide-allergic patients.

Materials and methods: A comprehensive PubMed search (1908-2021) was conducted using terms like Toxoplasma gondii, ocular toxoplasmosis, posterior uveitis, and retinochoroiditis. Priority was given to studies published after 2000, particularly those from 2010 onwards. Google Scholar, as well as English and Spanish sources, were also utilized.

Results: Ocular toxoplasmosis is the most common infectious form of posterior uveitis worldwide, typically presenting as necrotizing retinochoroiditis with associated vitreomacular adhesion and vitritis. Diagnosis is mainly clinical, supported by serology (IgG/IgM) and PCR of intraocular fluids when needed. Standard treatment includes systemic antiparasitic agents (e.g., pyrimethamine with sulfadiazine or trimethoprim-sulfamethoxazole) plus corticosteroids. In patients with sulfonamide allergies, alternatives such as pyrimethamine with clindamycin or azithromycin, or intravitreal clindamycin with dexamethasone, are effective. Recent studies show comparable outcomes with these regimens. Prompt treatment of active disease helps reduce retinal damage.

Discussion: Recent evidence supports the efficacy and safety of non-sulfonamide regimens and intravitreal therapies in managing ocular toxoplasmosis. These options are particularly valuable for patients with contraindications to standard treatments. Advances in imaging and molecular diagnostics have also enhanced early recognition and tailored management of the disease, contributing to improved visual outcomes.

Conclusion: Advances in diagnostic tools (PCR, intraocular antibody detection) and alternative therapies have improved outcomes in ocular toxoplasmosis, including in patients who are intolerant to sulfonamides. Clindamycin-based or intravitreal approaches offer effective, safe options. Further research is needed to refine treatment protocols, prevent recurrences, and clarify disease pathogenesis.

Keywords: CNV = Choroidal Neovascularization; FA = Fluorescein Angiography; GWC = Goldmann-Witmer Coefficient; ICGA = Indocyanine Green Angiography; IOP = Intraocular Pressure; OCT = Optical Coherence Tomography; OCTA = Optical Coherence Tomography Angiography; PCR = Polymerase Chain Reaction; PORT = Punctate Outer Retinal Toxoplasmosis; RPE = Retinal Pigment Epithelium; TMP-SMX = Trimethoprim-Sulfamethoxazole; VEGF = Vascular Endothelial Growth Factor; alternative treatment; antibiotic therapy; immunology; ocular infection; ophthalmology; retinochoroiditis; sulfonamide allergy; toxoplasmosis; uveitis.