**Core Concept**
Isoniazid is a first-line antitubercular medication used in the treatment of tuberculosis. Its daily dose is crucial for effective treatment and minimizing side effects.

**Why the Correct Answer is Right**
The daily dose of isoniazid in the treatment of tuberculosis is 5 mg/kg, not to exceed 300 mg. This dose is sufficient to achieve therapeutic levels of the medication in the body, which is essential for killing Mycobacterium tuberculosis. The dose is also designed to minimize the risk of side effects, such as peripheral neuropathy and hepatotoxicity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a dose in relation to the patient's weight, which is necessary for accurate dosing of isoniazid.
**Option B:** This option is incorrect because it is too high, exceeding the recommended maximum dose of 300 mg.
**Option C:** This option is incorrect because it does not provide a clear dose in relation to the patient's weight, making it an ineffective option for treatment.

**Clinical Pearl / High-Yield Fact**
When prescribing isoniazid, it's essential to consider the patient's weight and not exceed the maximum dose of 300 mg to minimize the risk of side effects.

**Correct Answer: D. 5 mg/kg, not exceeding 300 mg**