Promising Outcomes of Oral Doxycycline as Treatment for Ocular Syphilis in a Large Safety Net Hospital

Abstract

Purpose : Standard of care treatment for neurosyphilis, and therefore ocular syphilis (OS), is 10-14 days of intravenous (IV) penicillin (PCN). This places a significant burden on patients and the medical system, requiring prolonged inpatient stay or complex home care. Studies have shown similar efficacy of oral doxycycline (DOX) to IV PCN in treatment of neurosyphilis. In January 2022, infectious disease specialists of a large metropolitan safety net hospital began offering outpatient oral DOX as an alternative treatment through shared medical decision-making. This case series compares the clinical course and outcomes of patients with OS treated with standard IV PCN versus oral DOX.

Methods : This is a retrospective case series of patients with OS diagnosed from January 2022 to August 2023 at a large public hospital. Visual acuity (VA), clinical exam, and laboratory test results including serum RPR titers were compared between initial visits, 2 to 4-week follow-up, and 3-month follow-up.

Results : Fourteen patients were identified, of which 6 received standard-of-care IV PCN, 5 received oral DOX, and 3 received sub-standard IV PCN (less than 10 days) then were transitioned to oral DOX (PCN+DOX). Median (IQR) age was 45.5 (42-53) years; 21% were female. Twenty-six eyes were involved, with most presenting as panuveitis (61%) or posterior uveitis (23%). All 26 eyes showed clinical improvement in inflammation (e.g., anterior cell, vitritis, disc edema) at the 2 to 4-week follow-up. Only 1 PCN patient, 3 DOX patients, and 2 PCN+DOX patients could return for 3-month follow-up due to insurance reasons, however, all eyes at 3-month follow-up demonstrated quiescence. No patients in the DOX or PCN+DOX groups required rescue IV PCN. Final VA were similar between PCN and DOX groups (PCN group: VA improved from 20/200 (20/60-CF) to 20/50 (20/40-20/70) at 2 to 4-week follow-up; DOXY group: VA improved from 20/65 (20/40-20/300) to 20/45 (20/25-20/70); PCN+DOX group: VA improved from 20/100 (20/80-CF) to 20/80 (20/60-20/80)). At 3-month follow-up, VA of all patients were maintained or improved. One of 2 DOX patients and 2 of 2 PCN+DOX patients achieved adequate serological response (4-fold decrease in RPR titer) within the study timeframe.

Conclusions : Oral doxycycline may be an effective outpatient alternative to IV penicillin for the treatment of ocular syphilis, however more and longer-term studies are needed.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.