Which of the following is the primary site of activity for the drug Warfarin?

Correct Answer: B

Rationale: The correct answer is B: Liver. Warfarin is primarily metabolized in the liver by the cytochrome P450 enzyme system. The liver is responsible for breaking down and activating many drugs, including Warfarin. It is where the drug's metabolism and effects are most significant. The other choices are incorrect because Warfarin's main site of activity is in the liver, not the kidney, blood, or heart. The kidney mainly excretes the drug, while the blood carries it throughout the body, and the heart is not directly involved in Warfarin's metabolism.

Correct Answer: B

Rationale: The correct answer is B: Quinidine. Cinchonism is a condition caused by the toxicity of Cinchona alkaloids, which are found in drugs like quinine and quinidine. Quinidine is specifically known to cause symptoms of cinchonism such as tinnitus, headache, blurred vision, and nausea. Valproic acid (choice A) is an anticonvulsant, not associated with cinchonism. Isoniazid (choice C) is an antibiotic used to treat tuberculosis and does not cause cinchonism. Ethosuximide (choice D) is an anticonvulsant used to treat absence seizures and is not linked to cinchonism.

Correct Answer: C

Rationale: Correct Answer: C (Isoniazid) Rationale: 1. Isoniazid is known to cause drug-induced hepatitis due to its hepatotoxic effects. 2. It can lead to liver inflammation, causing hepatitis as a reaction. 3. Regular monitoring of liver function tests is essential when using isoniazid. Summary of other choices: A. Valproic acid: Can cause hepatotoxicity but not specifically linked to hepatitis. B. Quinidine: Mainly known for cardiac side effects, not commonly associated with hepatitis. D. Ethosuximide: Primarily used for treating absence seizures, not typically associated with hepatitis.

Correct Answer: D

Rationale: Step 1: Ethosuximide is the correct answer as it is a known trigger for Stevens-Johnson syndrome due to its association with hypersensitivity reactions. Step 2: Valproic acid can cause liver toxicity but is not typically linked to Stevens-Johnson syndrome. Step 3: Quinidine is associated with drug-induced lupus but not commonly known to cause Stevens-Johnson syndrome. Step 4: Isoniazid is linked to drug-induced hepatitis but not typically associated with Stevens-Johnson syndrome. In summary, Ethosuximide is the correct choice due to its well-documented association with Stevens-Johnson syndrome, while the other options are linked to different adverse effects.

Correct Answer: D

Rationale: The correct answer is D: Fluoroquinolones. Fluoroquinolones are known to be associated with tendon dysfunction due to their potential to cause tendinitis and tendon rupture. This adverse effect is thought to be related to the drug's ability to disrupt collagen synthesis and structure in tendons. Digitalis (A) is used to treat heart conditions, niacin (B) for cholesterol, and tetracycline (C) for bacterial infections, none of which are linked to tendon dysfunction.