Which of the following antienzymes is a cholinesterase inhibitor?

Correct Answer: A

Rationale: Physostigmine is the correct answer as it is a cholinesterase inhibitor. Cholinesterase inhibitors prevent the breakdown of acetylcholine, leading to increased cholinergic activity. Physostigmine specifically inhibits both acetylcholinesterase and butyrylcholinesterase. This action results in increased levels of acetylcholine in the synaptic cleft, enhancing cholinergic transmission. This mechanism is used in the treatment of conditions such as myasthenia gravis and glaucoma. Selegiline (B) is a monoamine oxidase inhibitor used in the treatment of Parkinson's disease. Aminocaproic acid (C) is an antifibrinolytic agent used to treat excessive bleeding. Disulfiram (D) is an alcohol deterrent used in the management of alcohol dependence by inhibiting aldehyde dehydrogenase. These choices are incorrect as they do not act as cholinesterase inhibitors.

Correct Answer: D

Rationale: Step 1: Phosphorus is primarily excreted renally. Step 2: Calcitonin is a hormone that regulates calcium and phosphorus metabolism. Step 3: Calcitonin inhibits renal reabsorption of phosphorus. Step 4: Therefore, Calcitonin increases renal excretion of phosphorus. Step 5: This mechanism makes option D correct. Summary: A: Amiloride doesn't directly affect phosphorus excretion. B: Glucocorticoids affect calcium absorption, not phosphorus. C: Loop diuretics increase sodium and water excretion, not phosphorus.

Correct Answer: A

Rationale: Loop diuretics act by competitively blocking the Na+/K+/2Cl- cotransporter in the thick ascending limb of the loop of Henle. By inhibiting this transporter, loop diuretics prevent reabsorption of sodium, potassium, and chloride ions, leading to increased urine output. Thiazide diuretics work in the distal convoluted tubule by blocking the Na+/Cl- cotransporter. Potassium-sparing diuretics act on the collecting duct or distal tubule to inhibit sodium reabsorption and potassium secretion. Carbonic anhydrase inhibitors work in the proximal convoluted tubule by inhibiting the enzyme carbonic anhydrase, which reduces bicarbonate reabsorption. Therefore, the correct answer is A because loop diuretics specifically target the Na+/K+/2Cl- cotransporter in the loop of Henle.

Correct Answer: A

Rationale: The correct answer is A: Oxacillin. Oxacillin is penicillinase-resistant due to its side chain that protects it from penicillinase enzymes. This side chain confers resistance against beta-lactamase enzymes produced by certain bacteria. On the other hand, choices B, C, and D are not penicillinase-resistant. Amoxicillin and Penicillin G are susceptible to penicillinase enzymes, while Bicillin-5 is a combination of penicillin G and penicillinase-sensitive benzathine penicillin. Thus, Oxacillin is the only penicillinase-resistant drug among the options provided.

Correct Answer: A

Rationale: The correct answer is A: Pyrazinamide. Pyrazinamide is not a bactericidal drug but rather a bacteriostatic drug. It inhibits the growth of mycobacteria rather than directly killing them. Streptomycin, Rifampin, and Isoniazid are all bactericidal drugs that directly kill mycobacteria. Streptomycin disrupts protein synthesis, Rifampin inhibits RNA synthesis, and Isoniazid inhibits mycolic acid synthesis in mycobacteria, leading to their death. Therefore, Pyrazinamide is the only drug among the options that does not have a bactericidal effect.