**Core Concept**
Meniere's disease is a disorder of the inner ear that affects balance and hearing. Chemical labyrinthectomy is a procedure to destroy the balance organs in the inner ear to alleviate vertigo symptoms. The procedure involves the transtympanic route, where a drug is injected into the middle ear to reach the inner ear.

**Why the Correct Answer is Right**
The correct drug used for chemical labyrinthectomy in Meniere's disease is Gentamicin. Gentamicin is an aminoglycoside antibiotic that is toxic to the vestibular hair cells in the inner ear. When injected into the middle ear, it selectively destroys the vestibular hair cells, leading to a reduction in vertigo symptoms. The mechanism of action involves the binding of Gentamicin to the ribosomes of the vestibular hair cells, leading to their death.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a commonly used drug for chemical labyrinthectomy in Meniere's disease.
**Option B:** This option is incorrect because it is not a suitable drug for chemical labyrinthectomy due to its toxicity profile and lack of selectivity for vestibular hair cells.
**Option C:** This option is incorrect because it is not a commonly used drug for chemical labyrinthectomy in Meniere's disease.

**Clinical Pearl / High-Yield Fact**
It is essential to note that Gentamicin should be used with caution in patients with pre-existing renal impairment, as it can exacerbate kidney function. A thorough audiogram and vestibular assessment should be performed before and after the procedure to monitor the patient's hearing and balance.

**Correct Answer:** D. Gentamicin