By in vitro visible electron paramagnetic resonance (EPR) spectrophotometry method we demonstrated that N-isonicotinoyl-N’-(3-etoxy-2-hydroxybenzaldehyd) hydrazone (SH11) exhibits radical scavenging activity (SSA). Malondialdehyde (MDA) in mice treated with INH was increased (2.578 ± 0.349 mM vs. 2.024 ± 0.164 μM, p < 0.001), while both superoxide dismutase (SOD) (1.583 ± 0.562 U_SOD/mg Pr vs. 2.273 ± 0.317 U_SOD/mg Pr, p < 0.05) and catalase (CAT) (30.176 ± 7.300 U_CAT/mg Pr, vs. 47.070 ± 16.490 U_CAT/mg Pr, p < 0.05) were decreased, compared to the untreated controls. The combination INH + SH11 (30 mg/kg p.o.) showed reduced levels of MDA, compared to the INH-treated (mean 2.291 ± 0.025 μM than 2.578 ± 0.349, p < 0.05). The combination with the lowest reduction of SOD compared to the controls was 151 mg/kg i.p. INH + 30 mg/kg p.o. SH11, but there was a significant difference in SOD activities between the group treated with this combination and the untreated controls (p < 0.05). The most effective combination, with CAT levels, close to the controls was 151 mg/kg i.p. INH + 30 mg/kg p.o. SH11.