**Question:** Pigmented lesions of oral mucosa do occur because of the consumption of following drug EXCEPT

A. Aspirin
B. Dapsone
C. Isoniazid
D. Penicillin

**Core Concept:**

Pigmented lesions of oral mucosa can result from various medications, indicating their potential side effects. The correct answer is not related to the side effects of the listed drugs. In this case, we will discuss the side effects of Aspirin, Dapsone, Isoniazid, and Penicillin, which can lead to oral pigmentation.

**Why the Correct Answer is Right:**

Aspirin (salicylic acid) is a nonsteroidal anti-inflammatory drug (NSAID) commonly used for pain relief, fever reduction, and inflammation management. Although Aspirin is generally safe, oral pigmentation can occur in some patients. The mechanism involves the inhibition of prostaglandin synthesis, which plays a crucial role in maintaining oral mucosa health and repair.

Dapsone (a sulfonamide antibiotic) is used for treating leprosy, leishmaniasis, and certain skin diseases. Dapsone-induced oral pigmentation is a known side effect. This occurs due to the drug's ability to inhibit the synthesis of heme, a component of hemoglobin and other proteins containing iron.

**Why Each Wrong Option is Incorrect:**

Isoniazid is an antitubercular drug primarily used in the treatment of tuberculosis. Although oral pigmentation is a rare side effect of Isoniazid, it is less likely compared to the other options.

Penicillin is a beta-lactam antibiotic used to treat bacterial infections. Oral pigmentation is a rare side effect associated with penicillin administration, but less likely compared to the other options.

**Clinical Pearl:**

While all the listed drugs can cause oral pigmentation, the question implies that Dapsone is the most likely option to cause oral pigmentation. This is due to its direct inhibition of heme synthesis, which is essential for hemoglobin and other proteins containing iron. Proper patient counseling about the potential side effects of these medications is crucial, particularly for Dapsone and Aspirin, as oral pigmentation may significantly affect the patient's quality of life.