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 [5000 to 10,000/mm3 (5 to 10 x 10%)]

A) Decreased blood urea nitrogen (BUN) is not a typical adverse effect of gentamicin. Gentamicin is primarily associated with nephrotoxicity (kidney damage), which would manifest as an increased BUN and serum creatinine rather than a decrease. B) Hearing loss is a well-known adverse effect of gentamicin, particularly when the drug reaches high concentrations in the inner ear (ototoxicity). Gentamicin can cause irreversible damage to the cochlear and vestibular organs, leading to sensorineural hearing loss and balance disturbances. C) Reports of photophobia are not typically associated with gentamicin. Photophobia (sensitivity to light) may occur with certain eye conditions or central nervous system disorders but is not a direct adverse effect of gentamicin. D) A white blood cell count of 6,000/mm3 falls within the normal reference range, so it does not indicate an adverse effect of gentamicin. Gentamicin is not known to directly affect white blood cell count.