Which first line antitubercular drug can result in adverse effects of Eye?
**Core Concept**
The question tests the knowledge of antitubercular medications and their potential side effects, specifically on the eye. **Ethambutol** is a first-line antitubercular drug that can cause optic neuritis, leading to visual disturbances.
**Why the Correct Answer is Right**
Ethambutol works by inhibiting the synthesis of mycolic acid, an essential component of the Mycobacterium tuberculosis cell wall. However, this mechanism of action can also lead to the drug's adverse effects, including optic neuritis. This condition results from the damage to the optic nerve, causing visual acuity loss, color vision defects, and even blindness. Ethambutol-induced optic neuritis is a well-known side effect, and patients on this medication require regular monitoring of their visual acuity.
**Why Each Wrong Option is Incorrect**
**Option A:** **Isoniazid** is another first-line antitubercular drug, but it is not commonly associated with eye-related side effects. Instead, isoniazid can cause peripheral neuropathy, hepatitis, and other systemic adverse effects.
**Option B:** **Rifampicin** is a key component of first-line antitubercular therapy, but it is not typically linked to eye problems. Rifampicin can cause hepatotoxicity, skin pigmentation, and other side effects, but eye-related issues are rare.
**Option C:** **Pyrazinamide** is another first-line antitubercular drug, but it is not commonly associated with eye-related side effects. Pyrazinamide can cause hepatotoxicity, arthralgias, and other systemic adverse effects.
**Clinical Pearl / High-Yield Fact**
To remember the common side effects of antitubercular drugs, use the mnemonic "HEART": Hepatitis (Isoniazid), Eye (Ethambutol), Arthralgias (Pyrazinamide), and Rifampicin-induced hepatotoxicity.
**Correct Answer:** A. Ethambutol.