A 28-year-old female presents with a 4 × 5 cm purulent ulcer on her abdomen following a spider bite. A wound culture grows MRSA, so intravenous vancomycin is started. While receiving her first dose of vancomycin, her face, neck, and chest flushed red. This reaction can best be described as

Correct Answer: A

Rationale: Vancomycin's red man syndrome-flushing during infusion-is non-hypersensitivity mast cell degranulation . Rapid infusion triggers histamine release, not IgE-mediated allergy . Type II , III , and IV (E) involve immune mechanisms unrelated to this acute, rate-dependent reaction. Slowing infusion prevents it, distinguishing it from true hypersensitivity, aligning with vancomycin's pharmacology in MRSA treatment.

Correct Answer: B

Rationale: Cyanocobalamin, or vitamin B12, is essential for red blood cell production and neurological function, and its deficiency directly leads to pernicious anemia, a condition characterized by large, immature red blood cells due to impaired DNA synthesis. This occurs because B12 is crucial for folate metabolism and erythropoiesis, and without it, anemia develops, often accompanied by neurological symptoms like numbness or tingling. Pellagra, however, results from niacin (vitamin B3) deficiency, manifesting as dermatitis, diarrhea, and dementia-unrelated to B12's role. Rickets stems from vitamin D deficiency, causing bone deformities due to poor calcium absorption, not a B12 issue. Scurvy arises from vitamin C deficiency, leading to collagen breakdown and symptoms like bleeding gums, distinct from B12's hematological effects. Pernicious anemia stands out as the correct outcome because B12 deficiency disrupts bone marrow function, and it often requires pharmacotherapy, such as B12 injections, especially if absorption is impaired (e.g., due to lack of intrinsic factor). This specificity eliminates other conditions, highlighting B12's unique role in blood and nerve health.

Correct Answer: C

Rationale: A large-bore catheter is recommended for whole blood transfusions to allow for the rapid administration of blood products and to prevent hemolysis. Smaller catheters may not accommodate the viscosity of whole blood and could increase the risk of complications. While patient comfort and past experiences are important, the primary consideration is the safe and effective delivery of the transfusion. Therefore, a large-bore catheter is the best choice.

Correct Answer: C

Rationale: Ionized drugs cross renal tubular membranes poorly, staying in urine for excretion, unlike non-ionized or lipid-soluble drugs reabsorbed easily. Volatile drugs (e.g., anesthetics) excrete via lungs, not kidneys. Ionization traps drugs, a pharmacokinetic excretion key.

Correct Answer: A

Rationale: Oxytetracycline's bioavailability increases in the fasting state as food, particularly calcium, can bind the drug and reduce its absorption.