Which drug is NOT associated with toxic side effects in the inner ear?

The correct answer is Penicillin, as it is generally not associated with toxic side effects in the inner ear. Penicillin is an antibiotic commonly used to treat bacterial infections and has a well-established safety profile without significant ototoxic effects.

In contrast, Gentamicin is an aminoglycoside antibiotic known for its potential to cause ototoxicity, which can lead to hearing loss and balance issues due to its damaging effects on the inner ear structures. Aspirin, particularly at high doses, can also lead to tinnitus and hearing loss due to its effects on cochlear function. Furosemide, a loop diuretic, can cause ototoxicity, especially when used in high doses or in patients with renal impairment, as it can affect electrolyte balance in the inner ear.

This understanding highlights the relatively safe profile of Penicillin concerning inner ear toxicity compared to the other drugs mentioned.