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 x 109/L)]

A. Decreased blood urea nitrogen: Gentamicin is more commonly associated with nephrotoxicity, which would manifest as an increase in blood urea nitrogen (BUN) and creatinine. A decreased BUN is not indicative of gentamicin toxicity, so this finding does not suggest an adverse effect. B. Reports of photophobia: Photophobia is not a typical adverse effect of gentamicin. While ocular symptoms can occur with certain medications, gentamicin’s primary toxicities involve the kidneys and the ears, not light sensitivity. C. Hearing has decreased: Gentamicin is an aminoglycoside antibiotic with known ototoxic potential. Sensorineural hearing loss, tinnitus, or vertigo are key indicators of ototoxicity. A decrease in hearing after several days of IV gentamicin strongly suggests the client is experiencing this adverse effect, which requires prompt reporting and potential discontinuation. D. White blood cell count of 6,000/mm3 (6 x 10⁹/L): This WBC value falls within the normal reference range of 5,000–10,000/mm³. Gentamicin does not typically cause significant leukopenia. Therefore, this finding does not indicate an adverse reaction to the medication.