The following drug is indicated in the treatment of pityriasis versicolar :
**Core Concept**
Pityriasis versicolor is a common skin condition caused by the overgrowth of Malassezia yeast on the skin's surface. The condition is characterized by patches of discoloration and scaling on the skin, often on the chest, back, and shoulders. Effective treatment involves antifungal agents that target the yeast.
**Why the Correct Answer is Right**
The correct answer is a topical antifungal agent that inhibits the growth of Malassezia yeast. This is achieved through the inhibition of ergosterol synthesis, a critical component of fungal cell membranes. The drug works by targeting the enzyme lanosterol 14Ξ±-demethylase, which is essential for the conversion of lanosterol to ergosterol. By inhibiting this enzyme, the drug prevents the formation of ergosterol, ultimately leading to the death of the yeast cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not an antifungal agent. Instead, it is a topical corticosteroid used to treat inflammatory skin conditions, which is not the primary mechanism of action for treating pityriasis versicolor.
**Option B:** This option is incorrect because it is an antihistamine, not an antifungal agent. Antihistamines are used to treat allergic reactions, itching, and hives, but they do not have a role in treating fungal infections like pityriasis versicolor.
**Option C:** This option is incorrect because it is a topical retinoid, not an antifungal agent. Topical retinoids are used to treat acne, psoriasis, and other skin conditions characterized by abnormal cell growth and differentiation, but they do not have a role in treating fungal infections.
**Clinical Pearl / High-Yield Fact**
When treating pityriasis versicolor, it is essential to use an antifungal agent that targets the yeast, rather than just treating the symptoms of the condition. This is because the condition is caused by an overgrowth of yeast on the skin's surface, and simply treating the symptoms may not address the underlying cause.
**Correct Answer:** C. Clotrimazole