**Core Concept**
Nodulocystic acne is a severe form of acne characterized by large, painful nodules and cysts on the skin. The treatment of choice for this condition involves the use of isotretinoin, a derivative of vitamin A that has anti-inflammatory and comedolytic properties.

**Why the Correct Answer is Right**
Isotretinoin works by decreasing the size of the sebaceous glands, reducing the production of sebum, and preventing the formation of comedones. It also has anti-inflammatory effects that reduce the severity of acne lesions. Isotretinoin is particularly effective in treating nodulocystic acne due to its ability to target the root cause of the condition, which is the overproduction of sebum by the sebaceous glands.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because doxycycline, a tetracycline antibiotic, is often used to treat mild to moderate acne but is not the drug of choice for nodulocystic acne.
**Option B:** This option is incorrect because benzoyl peroxide, a topical antibiotic, is effective against mild to moderate acne but is not sufficient to treat severe nodulocystic acne.
**Option C:** This option is incorrect because corticosteroids are sometimes used to treat acne but are not the primary treatment for nodulocystic acne.

**Clinical Pearl / High-Yield Fact**
Isotretinoin is a teratogenic medication, meaning it can cause severe birth defects if taken during pregnancy. Therefore, female patients taking isotretinoin must use two forms of birth control and undergo regular pregnancy testing.

**Correct Answer: C. Isotretinoin**