Pyridoxine levels in healthy patients receiving isoniazid for latent tuberculosis infection

<bold>Introduction:</bold> Isoniazid (INH) is a standard treatment for latent tuberculosis infection (LTBI). INH may cause vitamin B6 (pyridoxal phosphate PLP) deficiency in active TB patients, and supplementation is recommended. There is limited data on changes in PLP levels under INH therapy in healthy LTBI patients and there are no evidence based recommendations for prophylaxis. <bold>Methods:</bold> Prospective observational cohort study. Patients treated for LTBI between 2021-2022 in a TB clinic in Israel were recruited. INH or rifampin (RIF, control group) was prescribed according to the clinician's preference. Demographic and clinical data was collected. Blood samples before and after 1 month of treatment were tested for PLP levels. Results were analyzed in a 2 way repeated-measures ANOVA where time (0,1) and LTBI drug (INH,RIF) were independent variables. <bold>Results:</bold> Sixty-three patients were included in the study, 39 INH, 24 in the RIF (control) group. Demographic and clinical characteristics were similar, with no statistical differences between groups. PLP levels (mcg/L) in both groups were similar at baseline [8.7(7.8) INH, 10.3 (7.9) RIF], and no reduction of B6 levels were shown after 1 month of treatment [12.8 (17.3) INH , 8 (3.7) RIF] : F(df) (treatment 1.73(1,117) , time 0.92(1,117), interaction 0.90(1,17)) , p>0.05 in all). Table 1. No patients in either group developed B6 levels outside the normal range or clinical symptoms of B6 deficiency. <bold>Conclusion:</bold> In healthy patients receiving INH for LTBI, PLP levels remained stable in patients treated with INH and RIF for one month with no between-group differences. These data do not support the routine use of vitamin B6 in these patients.