Correct Answer: C

Rationale: The correct answer is C: IgE. A severe allergic reaction, such as the one experienced by the 10-year-old male after being stung by a bee, is mediated by IgE. IgE is involved in common allergic responses, triggering the release of histamine and other chemicals that lead to allergy symptoms. Choice A, Toxoids, are inactivated toxins used in vaccines. Choice B, IgA, is mainly found in mucosal areas and secretions, playing a role in mucosal immunity. Choice D, IgM, is the first antibody produced in response to an infection.

Correct Answer: B

Rationale: In patients with chronic renal failure, especially in older adults, dosages of medications excreted renally need to be adjusted based on kidney function. Acyclovir is primarily eliminated by the kidneys, so in a patient with chronic renal failure, the dose would need to be smaller to prevent drug accumulation and toxicity. Choice A is incorrect because the dose adjustment is more related to the patient's kidney function than the presence of herpes simplex. Choice C is incorrect because the type of herpes infection does not determine the dose adjustment for acyclovir. Choice D is incorrect as the creatinine clearance is a more accurate measure of kidney function compared to creatinine levels.

Correct Answer: A

Rationale: The correct answer is A. Alendronate should be taken with a full glass of water and patients should remain upright for at least 30 minutes to prevent esophageal irritation and ensure proper absorption. Taking the medication with milk (choice B) is not recommended as it may interfere with the absorption of alendronate. Taking the medication at bedtime (choice C) is not necessary for optimal absorption. Taking the medication with food (choice D) is also not recommended as food can reduce the absorption of alendronate.

Correct Answer: A

Rationale: The correct answer is A. Sildenafil is contraindicated in patients taking nitrates due to the risk of severe hypotension. Nitrates and sildenafil both cause vasodilation, leading to a synergistic effect that can result in a dangerous drop in blood pressure. Choices B, C, and D are incorrect because there is no specific contraindication for taking sildenafil with food, having a history of hypertension, or taking it with grapefruit juice. The main concern is the concurrent use of nitrates with sildenafil.

Correct Answer: C

Rationale: The correct answer is bone density testing (Choice C). Long-term use of Depo Provera, a hormonal contraceptive, is associated with decreased bone mineral density. Assessing bone density is crucial to monitor for potential osteoporosis. Cardiac stress testing (Choice A) is not indicated based on the medication history provided. Renal ultrasound (Choice B) and evaluation of triglyceride levels (Choice D) are not directly related to the use of Depo Provera.