A male client has been receiving the antibiotic gentamicin sulfate, IV piggyback, every 12 hours for several days. Which observation by the nurse indicates that the client may be experiencing an adverse effect of gentamicin? Reference Range: White Blood Cell [5,000 to 10,000/mm³ (5 to 10 × 10⁹/L)]

Choice A reason: Gentamicin is an aminoglycoside antibiotic known for its potential ototoxicity and nephrotoxicity. Ototoxicity manifests as hearing loss, tinnitus, or balance disturbances due to damage to the cochlea or vestibular system. Hearing loss is a classic adverse effect and requires immediate intervention to prevent permanent damage. This observation is the most concerning and directly linked to gentamicin toxicity. Choice B reason: A decreased blood urea nitrogen (BUN) is not typically associated with gentamicin toxicity. Gentamicin can cause nephrotoxicity, which would lead to increased BUN and creatinine levels, not decreased. Therefore, this finding does not indicate an adverse effect of gentamicin. Choice C reason: Photophobia is sensitivity to light and is not a recognized adverse effect of gentamicin. It may occur with other conditions or medications but is not related to aminoglycoside toxicity. This observation is not relevant to gentamicin use. Choice D reason: A white blood cell count of 6,000/mm³ is within the normal reference range (5,000–10,000/mm³). This finding does not indicate an adverse effect of gentamicin. Normal WBC levels suggest no hematologic toxicity or infection-related complication.