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  • Uveitis

    As the use of proton pump inhibitors (PPIs) and histamine-2 (H2) blockers has been surmised to have effects on the gut microbiome, investigators evaluated whether taking these medications is a potential risk factor for ocular toxoplasmosis development.

    Study design

    This retrospective, matched case-control study reviewed 20-year US health care database data from 4069 patients with toxoplasmic retinochoroiditis infection and 19,177 matched controls. The primary outcome measure was the odds of having filled a prescription for a PPI prior to onset of infection.


    Twenty-four percent of patients with ocular toxoplasmosis were on a PPI or H2 blocker compared with 19% of controls, leading to an adjusted odds ratio (OR) of 1.28 for known PPI/H2 blocker use among patients with ocular toxoplasmosis. Patients with ocular toxoplasmosis were also more likely to have filled a prescription for a PPI or H2 blocker than controls were (OR 1.23).


    The pathophysiologic theory behind the hypothesis assessed in this study is that PPIs increase gut pH, thereby potentially increasing the susceptibility of patients to Toxoplasma gondii infection by eliminating gut acidity as a defense against the organism. While interesting, there is no ability to account for patients taking PPIs over the counter, and recall bias may misrepresent the actual number of patients on PPIs. The authors state that this likely indicates underreporting of PPI use in both the ocular toxoplasmosis and control groups, but that the impact of these data would not change the overall results of the study.

    Clinical significance

    The data presented in this paper are interesting and should increase physician awareness of the potential association between PPI/H2 blocker use and ocular toxoplasmosis. Studies to investigate the mechanism of action behind these findings should be pursued. Further study to determine whether ongoing PPI use increases the risk of ocular toxoplasmosis reactivation would be helpful; it is likely that once the infection is acquired, the postulated pathophysiologic mechanism by which this susceptibility occurs would not impact ongoing flares.

    Financial Disclosures: Dr. Arthi Venkat discloses financial relationships with Apellis Pharmaceuticals, EyePoint (Consultant/Advisor).