B47-35 A Silent Complication: Rare Case of Inhaled Tobramycin Associated Ototoxicity in Patient With Preserved Renal Function

Abstract Introduction Aminoglycoside antibiotics are well known to cause cochlear and vestibular toxicity when used systemically. Inhaled tobramycin was developed to reduce systemic exposure and is considered safer with only rare reports of ototoxicity have been reported in patients with renal dysfunction. We describe a case of bilateral sensorineural hearing loss (SNHL) and tinnitus associated with inhaled tobramycin in a patient without renal impairment, emphasizing that even inhaled formulations can induce significant auditory toxicity in susceptible individuals. Case A 85 year old woman with Sjogren’s related interstitial lung disease and bronchiectasis who was chronically colonized by Pseudomonas aeruginosa was treated with inhaled tobramycin for recurrent infections. She had normal renal function and no prior aminoglycoside exposure. After approximately three months of inhaled therapy, she noted progressive bilateral hearing decline and high pitched tinnitus without vertigo or otalgia. Physical examination revealed clear ear canals and intact tympanic membranes. Baseline audiometry one year ago had demonstrated mild to moderately-severe bilateral SNHL. Repeat testing after tobramycin exposure showed worsening thresholds and reduced word recognition bilaterally. MRI of the brain and internal auditory canals was unremarkable. Serum creatinine remained normal throughout treatment. Inhaled tobramycin was discontinued, after which hearing loss stabilized. No further progression was observed on follow-up audiometry. Discussion Although systemic absorption from inhaled tobramycin is typically low, elderly and low-body-weight patients may accumulate sufficient serum levels to cause cochlear injury. Mechanisms include reactive oxygen species mediated hair cell toxicity and possible genetic susceptibility involving the mitochondrial 12S rRNA mutation. Prior reports of vestibulotoxicity and cochleotoxicity from inhaled tobramycin primarily involved patients with renal dysfunction, however, this case report demonstrates that toxicity can occur despite preserved renal function. Clinicians should maintain vigilance for otologic symptoms in patients receiving inhaled aminoglycosides. Baseline and periodic audiometric monitoring should be incorporated into chronic treatment protocols. This abstract is funded by: None