Unknown Renal Impairment: A Rare Case of Inhaled Tobramycin Induced Acute Kidney Injury in a Cystic Fibrosis Patient

Abstract

Acute kidney injury is a reversible medical condition commonly caused by nephrotoxic agents. The infrequency that a nebulized medication elicits a renal insult presents a rare diagnostic challenge. Within this case, we report a 57-year-old cystic fibrosis patient with chronic kidney disease (CKD) Stage G3b (baseline 1.5–1.6 mg/dL) who developed an acute kidney injury (AKI) with a serum creatinine elevation to 4.08 mg/dL and associated worsening vestibular dysfunction related to twice-daily nebulized tobramycin inhalation solution (TIS). The patient was found to have a tobramycin serum level of 4.2 μg/mL 2.5 h after TIS dosing, with elevation remaining present at 1.1 μg/mL 24 h after discontinuation of therapy. Laboratory values at one month continued to show elevated creatinine levels at 2.1 mg/dL, suggesting progression of his baseline CKD. This case supports the benefit of obtaining tobramycin serum levels and vestibular/audiology function testing when evaluating patients on chronic nebulized TIS who present with acute or chronic renal dysfunction. From these serum levels, adjustments to daily dosing, regular monitoring of tobramycin serum levels, or discontinuation of treatment should be made to prevent permanent renal damage in patients with CKD. Calculated Naranjo ADR Probability Scale: 9; Definite.

Assessment of Detectable Serum Tobramycin Concentrations in Patients Receiving Inhaled Tobramycin for Ventilator-Associated Pneumonia

“…Case reports in older adult subjects parallel to our groups also report AKI or vestibular toxicity with inhaled tobramycin. [25][26][27] The age range for these 4 case reports was 41-75-y old and involved subjects with a history of cystic fibrosis, solid-organ transplant, or had extensive comorbidities. The first case was a 41-y-old woman with a history of renal failure requiring hemodialysis that was on inhaled tobramycin 300 mg twice daily for Pseudomonas aeruginosa in her sputum.…”

Tobramycin Systemic Absorption in Lung Transplant Recipients Treated With Inhaled Tobramycin: A Cohort Study

“…However, there are few studies describing the systemic absorption of inhaled tobramycin. Detectable tobramycin levels have been reported, mainly in patients with cystic fibrosis and associated with nephrotoxicity in some cases [9][10][11]. Nevertheless, these findings have not been confirmed in other studies [12][13][14].…”