The following antifungal agents have been paired correctly with an appropriate indication:

Correct Answer: A

Rationale: Nystatin paired with oral Candida infections (A) is correct, as it's a topical polyene antifungal used for thrush, binding ergosterol to disrupt fungal membranes, with minimal systemic absorption. Voriconazole with invasive aspergillosis (B) is accurate, a first-line triazole for Aspergillus infections. Flucytosine with tinea pedis (C) is incorrect; it's used systemically for cryptococcosis or candidiasis, not dermatophytes (terbinafine is preferred). Clotrimazole with intertrigo (D), a Candida-related skin infection, is correct. Miconazole with cold sores (original E) is wrong; antivirals like aciclovir are used. Nystatin's non-absorbable nature makes it ideal for mucosal candidiasis, avoiding systemic side effects, though it's ineffective against deeper infections requiring agents like amphotericin.

Correct Answer: C

Rationale: Psychosis paired with mefloquine (C) is correct, a known neuropsychiatric side effect (e.g., hallucinations, anxiety), limiting its use in those with psychiatric history. Acneiform eruption with chloroquine (A) is rare; retinopathy is more typical. Stevens-Johnson syndrome with quinine (B) is incorrect; it's linked to hypersensitivity but not a hallmark. QTc prolongation with proguanil (D) is wrong; quinine causes this. Hemolytic anemia with primaquine (original E) is accurate in G6PD deficiency. Mefloquine's schizonticidal action is effective for prophylaxis and treatment, but its CNS toxicity, including rare seizures, necessitates careful patient selection and counseling.

Correct Answer: C

Rationale: Daunorubicin paired with cardiomyopathy (C) is correct, an anthracycline causing dose-dependent cardiotoxicity via oxidative stress and topoisomerase inhibition, common in leukemia treatment, mitigated by dexrazoxane. Etoposide (A) causes myelosuppression, not neuropathy (vincristine does). Paclitaxel (B) causes alopecia, a hallmark taxane effect. Irinotecan (D) causes diarrhea, due to cholinergic and mucosal damage. 6-Mercaptopurine with pulmonary fibrosis (original E) is incorrect; myelosuppression is typical. Daunorubicin's efficacy in acute leukemias is balanced by lifetime dose limits to protect cardiac function, monitored via echocardiography.

Correct Answer: B

Rationale: The correct answer is that the half-life is the same regardless of the plasma concentration (B). First-order kinetics implies that the rate of drug elimination is proportional to its plasma concentration, meaning a constant fraction of the drug is removed per unit time. This results in a consistent half-life, independent of the initial concentration, as seen with most drugs like aspirin. Option A is incorrect because multiple metabolic pathways can exist in first-order kinetics. Option C describes first-pass metabolism but isn't inherent to first-order kinetics. Option D is false as elimination rate depends on concentration, not administration rate. Option E (original) about vascular confinement is unrelated. This principle is foundational in pharmacokinetics, allowing predictable dosing regimens, unlike zero-order kinetics where half-life varies with concentration, as with ethanol.

Correct Answer: D

Rationale: A chemical antagonist (D) best describes an antagonist that interacts directly with the agonist, not the receptor, by neutralizing or binding it (e.g., protamine with heparin). Pharmacological antagonists (A) block receptors directly (e.g., propranolol). Partial agonists (B) bind receptors but produce submaximal effects (e.g., buprenorphine). Physiological antagonists (C) oppose effects via different receptors (e.g., epinephrine vs. histamine). Noncompetitive antagonists (original E) bind irreversibly to receptors, reducing efficacy. Chemical antagonism, a rare but specific mechanism, alters the agonist's availability without receptor interaction, critical in overdose reversal or chelation therapies, distinct from receptor-based antagonism in pharmacodynamics.