A 47-year-old woman is admitted to the hospital for treatment of pneumococcal pneumoniTreatment with gentamicin and penicillin is initiateWithin 10 minutes of the administration of antimicrobial therapy, her respirations increase to 30/min, and blood pressure decreases to 80/40 mm Hg. Epinephrine, antihistamine, and corticosteroid therapy is starteHer condition improves slowly during the next 2 hours. Her antimicrobial therapy is changed to gentamicin only, and her condition continues to improve. Administration of which of the following types of drugs is most likely to cause a similar adverse reaction in this patient?

Correct Answer: A

Rationale: The acute reaction (tachypnea, hypotension) post-penicillin, relieved by epinephrine and antihistamines, indicates an anaphylactic response to penicillin, a beta-lactam. Cephalosporins (A), also beta-lactams, have cross-reactivity (5-10%) with penicillin allergies, risking a similar reaction. Macrolides (B), quinolones (C), and tetracyclines lack this structural similarity and rarely cause anaphylaxis.

Correct Answer: A

Rationale: The correct answer is A: Atorvastatin. Atorvastatin belongs to a class of drugs known as statins, which are highly effective in lowering LDL cholesterol levels by inhibiting the enzyme responsible for cholesterol production in the liver. This mechanism of action has been proven to significantly reduce LDL cholesterol levels in the blood. In contrast, choice B (Gemfibrozil) primarily targets triglycerides and has limited impact on LDL cholesterol. Choice C (Ezetimibe) works by blocking cholesterol absorption in the intestines but is not as potent as statins in lowering LDL cholesterol. Choice D (Cholestyramine) is a bile acid sequestrant that binds to bile acids in the intestines, but it is less effective than statins in lowering LDL cholesterol. Overall, Atorvastatin is the most effective choice for reducing LDL cholesterol levels due to its potent mechanism of action.

Correct Answer: C

Rationale: The correct answer is C: Acne. Tretinoin is a topical retinoid that is commonly used to treat acne. It works by promoting skin cell turnover and preventing the formation of new acne lesions. Tretinoin is not used for psoriasis (A), seborrheic dermatitis (B), or multiple sclerosis (D) as these conditions require different treatment approaches.

Correct Answer: B

Rationale: Step 1: Drugs with a narrow therapeutic index have a small range between the minimum effective dose and the minimum toxic dose. Step 2: Genetic variants affecting drug metabolism can lead to small increases or decreases in drug levels. Step 3: Small increases can cause toxicity, while small decreases can lead to therapeutic failure. Step 4: Therefore, statement B is true as it correctly describes the impact of genetic variants on drug metabolism for drugs with a narrow therapeutic index. Summary: Statement A is incorrect as not all statements are true. Statement C is incorrect as drugs like warfarin are indeed affected by CYP2C9. Statement D is incorrect as drugs with a high therapeutic index are less affected by altered metabolism compared to drugs with a narrow therapeutic index.

Correct Answer: A

Rationale: The correct answer is A: Drug interactions. Elderly patients are at higher risk for drug interactions due to age-related changes in metabolism and multiple medications. This can lead to adverse effects, reduced efficacy, or toxicity. It is the highest priority as it directly impacts patient safety. Summary of other choices: B: Cost of medications - While important, it is not as critical as drug interactions for patient safety. C: Schedule of medications - Important for adherence but not as urgent as addressing potential drug interactions. D: Nonadherence to drug regimen - Also important, but drug interactions pose a more immediate risk to the patient's health.