A fungicidal drug that can be used orally for the treatment of onychomycosis is :
**Core Concept**
The question is testing the student's knowledge of antifungal medications used for treating onychomycosis, a fungal infection of the nails. The correct answer is a drug that has both fungicidal and oral bioavailability, making it suitable for treating onychomycosis.
**Why the Correct Answer is Right**
Terbinafine is a fungicidal drug that works by inhibiting the enzyme squalene epoxidase, which is essential for the synthesis of ergosterol in fungal cell membranes. By inhibiting this enzyme, terbinafine disrupts the cell membrane structure and ultimately leads to the death of the fungal cells. Terbinafine is available in oral formulations and is commonly used to treat onychomycosis, particularly for fungal infections of the toenails.
**Why Each Wrong Option is Incorrect**
**Option A:** Itraconazole is an antifungal medication, but it is not typically used orally for the treatment of onychomycosis. It is usually administered orally for systemic fungal infections.
**Option B:** Fluconazole is another antifungal medication, but it is not as effective as terbinafine for treating onychomycosis. It is often used for treating vaginal yeast infections and other systemic fungal infections.
**Option C:** Griseofulvin is an older antifungal medication that is used to treat fungal infections of the skin, hair, and nails. However, it is not as effective as terbinafine for treating onychomycosis and is not typically used orally for this indication.
**Clinical Pearl / High-Yield Fact**
When treating onychomycosis, it's essential to note that terbinafine has a higher success rate compared to other antifungal medications. A 12-week course of oral terbinafine can achieve a cure rate of up to 80% for toenail onychomycosis.
**Correct Answer:** C. Terbinafine.