“Crack” is a derivative of:

Correct Answer: C

Rationale: The correct answer is C: Cocaine. Crack cocaine is a highly addictive stimulant drug derived from cocaine. The process of making crack involves mixing cocaine with baking soda and water, then heating it to form small rocks or crystals. Crack is different from cocaine in that it is smoked rather than snorted, leading to a quicker and more intense high. Crack is not derived from opium (A), LSD (B), or cannabis (D). Opium is a narcotic derived from the opium poppy plant, LSD is a hallucinogenic drug, and cannabis is a plant that produces marijuana. Therefore, the correct answer is C as crack is a derivative of cocaine specifically.

Correct Answer: C

Rationale: The correct answer is C: Methotrexate. Methotrexate is a chemotherapy drug that inhibits cell division, including erythroid precursors, thereby suppressing erythrogenesis. Iron dextran, vitamin B12, and folic acid are essential for erythrogenesis by supporting hemoglobin synthesis and red blood cell production. Iron dextran provides iron for hemoglobin synthesis, vitamin B12 is required for DNA synthesis in erythroid precursors, and folic acid is essential for DNA synthesis and cell division. Therefore, methotrexate is the only drug among the choices that does not stimulate erythrogenesis.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Digibind (Digoxin immune fab) is the best choice in severe digitalis intoxication as it binds to digoxin, reducing its effects. 2. Lidocaine is used for cardiac arrhythmias but not specific to digoxin toxicity. 3. Oral potassium supplementation can worsen digoxin toxicity by increasing intracellular potassium. 4. Reducing the dose of the drug is not effective in severe intoxication. Summary: - Digibind is specific for digoxin toxicity by binding to the drug. - Lidocaine, oral potassium, and reducing the drug dose are not effective in severe digitalis intoxication.

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Calcium channel blockers are commonly used for angina pectoris, hypertension, and supraventricular tachyarrhythmias. They work by blocking the entry of calcium into the cells, leading to vasodilation, decreased myocardial contractility, and reduced heart rate. This helps in managing angina by reducing oxygen demand, controlling blood pressure, and treating certain types of arrhythmias. Therefore, the main clinical use of calcium channel blockers encompasses all three conditions mentioned in the choices.

Correct Answer: C

Rationale: The correct answer is C: Beta-1 adrenoreceptors (leads to enhanced cardiac output). Dopamine at medium doses mainly influences the Beta-1 adrenoreceptors in the heart, leading to increased heart rate and contractility, thus enhancing cardiac output. This is because dopamine acts as a positive inotropic and chronotropic agent on the heart. Choices A and B are incorrect because dopamine does not primarily act on Alfa-adrenoreceptors (A) causing peripheral vasoconstriction or dopamine receptors (B) causing vasodilation of renal and mesenteric vessels at medium doses. Choice D is incorrect because dopamine at medium doses primarily influences Beta-1 adrenoreceptors, not all the options listed.