Administration of NR prevents NIHL. C57BL/6 mice were tested for hearing loss at 24 hr, 7 d and 14 d after exposure to 2 hr of 90 dB noise. NR was administered at 1,000 mg/kg by intraperitoneal injection twice daily either for 5 d prior to noise exposure and 14 d after (NR All), 5 d prior to noise exposure (NR Before) or 14 d after exposure (NR After). NR treatment in all groups showed protection against transient hearing loss at 24 hr and permanent hearing loss at 14 d in comparison to vehicle controls, most notably at higher frequencies affected by noise exposure (16,000 and 32,000 Hz). Each point is the average threshold shift measured in 7 mice per group. Statistical analysis was performed using a two-way ANOVA followed by a Bonferroni post-test (**P < 0.01, ***P < 0.001). Error bars represent SD.