Pulmonary delivery of d-methionine is associated with an increase in ALCAR and glutathione in cochlear fluids

► d-met and ALCAR were administered by four systemic routes IV, IT, OG, & IN. ► Levels in cochlear tissues and fluids were measured by 14C counts and LC/MS. ► IT delivery resulted in the highest relative concentration of methionine & ALCAR. ► d-met IT administration increased both methionine & ALCAR levels in cochlear fluids. ► Antioxidants administered by IT could be a therapeutic tool for hearing protection.