Which of the following antienzymes is a xantine oxidase inhibitor?

Correct Answer: B

Rationale: The correct answer is B, Allopurinol. Allopurinol is a xanthine oxidase inhibitor, which helps reduce uric acid levels in conditions like gout. Xanthine oxidase is an enzyme involved in the production of uric acid. Physostigmine (A) is a cholinesterase inhibitor used in conditions like myasthenia gravis. Aminocaproic acid (C) is an antifibrinolytic agent. Acetazolamide (D) is a carbonic anhydrase inhibitor used in conditions like glaucoma and altitude sickness. Therefore, Allopurinol is the correct choice as a xanthine oxidase inhibitor.

Correct Answer: B

Rationale: The correct answer is B because pamidronate has a skeletal half-life of about 10 years, not 24 hours. A: Pamidronate is not available orally due to poor bioavailability and potential esophageal irritation. C: Fever and lymphocytopenia are reversible side effects of pamidronate. D: Pamidronate can irritate the esophagus if not washed down promptly to the stomach, leading to esophageal ulceration.

Correct Answer: C

Rationale: The correct answer is C: Potassium-sparing diuretics. Potassium-sparing diuretics act in the collecting tubules by blocking the sodium-potassium exchange, leading to decreased sodium reabsorption and potassium retention. This mechanism helps to promote diuresis while preventing potassium loss. Loop diuretics (A) act in the loop of Henle, thiazide diuretics (B) act in the distal convoluted tubule, and carbonic anhydrase inhibitors (D) act in the proximal convoluted tubule. Therefore, they are not directly involved in the collecting tubules like potassium-sparing diuretics.

Correct Answer: D

Rationale: The correct answer is D (All of the above) because all three choices (Clavulanic acid, Sulbactam, Tazobactam) are beta-lactamase inhibitors commonly co-administered with penicillins to enhance their efficacy. Beta-lactamase inhibitors work by inhibiting bacterial enzymes that can inactivate penicillins, allowing the antibiotic to remain effective against the bacteria. Clavulanic acid, Sulbactam, and Tazobactam are specifically designed to counteract beta-lactamase enzymes produced by bacteria, making them effective choices for combination therapy with penicillins. The other choices (A, B, C) are incorrect as each of them alone is a valid beta-lactamase inhibitor used in clinical practice.

Correct Answer: B

Rationale: The correct answer is B: Metronidazole. Metronidazole is a nitroimidazole derivative commonly used as an antibacterial and antiprotozoal drug. It works by disrupting the DNA structure of bacteria and parasites, leading to their death. Clavulanic acid (A) is a beta-lactamase inhibitor, not an antibacterial drug. Nitrofurantoin (C) is a nitrofuran derivative used for urinary tract infections, not a nitroimidazole derivative. Doxycycline (D) is a tetracycline antibiotic, not a nitroimidazole derivative. Therefore, the correct choice is B as it is the only nitroimidazole derivative among the options provided.