Final answer:
The nurse should withhold the medication and notify the provider if the client has an allergy to penicillin.
Step-by-step explanation:
In this case, the nurse should withhold the medication and notify the provider if the client has an allergy to penicillin. This is because gentamicin is an aminoglycoside antibiotic, and some individuals who are allergic to penicillin may also be allergic to aminoglycosides. It is important to avoid prescribing gentamicin to individuals with a known penicillin allergy to prevent an allergic reaction.
Other findings in the client's medical record, such as a history of recent dental work, an elevated white blood cell count, or pre-existing hearing loss, may be relevant to the client's overall health but do not specifically indicate the need to withhold gentamicin or notify the provider.