272. Clinical Utility of Sulfamethoxazole Serum Level Monitoring in the Treatment of Brain Abscesses due to Nocardia Species

Abstract

Abstract Background Although trimethoprim-sulfamethoxazole (TMP-SMX) has consistently demonstrated significant interindividual variability, therapeutic drug monitoring is used to optimize dosing and avoid adverse reactions that may contribute to treatment interruption. While data exists on the use of SMX level monitoring in pneumocystis, there is a lack of data in SMX serum monitoring utility for invasive Nocardia infections. Methods We retrospectively reviewed adults who received TMP-SMX to treat nocardial brain abscess (BA) and underwent SMX testing level from January 2010 to December 2020. Results Overall, 24 patients had Nocardia spp. BA; Twenty-two (91.7%) were treated with TMP-SMX, and 16/22 (72.7%) had a documented SMX serum level. The median age was 64 (IQR 58-69) years, and the majority were males (77.3%). Compared to those who did not have a documented SMX serum level, patients with SMX levels had a higher prevalence of hemodialysis (HD, 42.9% vs. 33%; P=.99) and malignancy (50% vs. 33.3%; P=.65). The most common BA location was the frontal lobe (43.8% vs. 33.3%; P=.99), with a single (68.8% vs. 50%; P=.62) and smaller (1.3 vs. 1.9 cm; P=.58) brain fluid collection, and with fewer midline shift (6.3% vs. 16.7%; P=.48), respectively. The median TMP-SMX duration was 350 days (P=.31). The most common dosing was 2-double strength, three times a day (31.8%). The SMX median level was 158.5 (IQR 120-218) mcg/mL, collected at two hours (75%) post-administration in the induction phase (81.3%). The most common recommendation was to continue therapy based on the level results. Eleven (46%) patients had a level >150 mcg/mL, and 5 (45.5%) reported drug toxicity, including nausea in 3, acute kidney injury in 2, and thrombocytopenia in 2 patients. Ninety-four percent of the patients with SMX levels had surgical intervention for therapeutic purposes vs. 83% of those without it (P=.65). A total of 11 (50%) patients were cured, 3 (18.8%) relapsed, and 2 (12.5%) died. Conclusion Patients with SMX serum level monitoring are more likely to be on HD, during the induction phase and among those with higher and more frequent dosing. About half of patients with SMX levels >150 mcg/mL experienced drug toxicity; however, SMX levels did not impact patient outcome and length of treatment. Disclosures All Authors: No reported disclosures