**Core Concept**
Isotretinoin is a potent second-generation oral retinoid used primarily for the treatment of severe, recalcitrant, and disabling acne. Its maximum dose is crucial to prevent adverse effects and ensure efficacy.

**Why the Correct Answer is Right**
The maximum dose of isotretinoin is determined by the patient's body weight. A commonly recommended maximum cumulative dose is 150 mg/kg of body weight. This dose is typically divided into 4-6 months of therapy. The rationale behind this dose is to balance efficacy with the risk of adverse effects, such as teratogenicity, hyperlipidemia, and bone changes. The dose is usually calculated based on the patient's initial weight, and adjustments are made as needed based on the patient's response and tolerance.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified and does not provide any information about the maximum dose of isotretinoin.
**Option B:** This option is not correct because the maximum dose of isotretinoin is not solely based on the patient's age.
**Option C:** This option is not correct because the maximum dose of isotretinoin is not solely based on the patient's sex.

**Clinical Pearl / High-Yield Fact**
To prevent teratogenic effects, isotretinoin should be discontinued at least 1 month before attempting conception. Additionally, women of childbearing age should be on two forms of reliable contraception during and for at least 1 month after isotretinoin therapy.

**Correct Answer: D. 150 mg/kg**