It does not seem anyone knows. They say the same about noise induced tinnitus, and yet in some cases people improve. Reversal or at least great reduction in volume is my only hope.
I feel like if a medication caused enough damage to hair cells for them to die off, thus creating T, the argument could be that the hair cell die off or whatever was physically damaged in the ear is permanent. Could this then lead to "permanent T"? Possibly, but the T itself could change over time and, hopefully, for the better as the brain acclimates.
@Ivanom that's what my ENT said. He said "maybe it will go away, maybe it won't." My audiologist said usually it's permanent after 6 months but she also said she's seen it go away after that, but the chances are lower.