Estimation of plasma/serum drug concentrations are most useful in optimizing the therapeutic dose required of:

Correct Answer: D

Rationale: Plasma concentration monitoring optimizes drugs with narrow therapeutic indices or variable pharmacokinetics. Warfarin uses INR, not plasma levels, for anticoagulation control. Omeprazole, a proton pump inhibitor, relies on symptom relief, not levels. Salbutamol, a bronchodilator, is titrated by response, not plasma monitoring. Olanzapine's dosing is guided by efficacy and side effects, not routine levels. Ciclosporin, an immunosuppressant, requires plasma monitoring (e.g., 100-400 ng/mL) due to its narrow therapeutic range, interindividual variability, and risk of toxicity or rejection in transplant patients. This ensures efficacy while minimizing nephrotoxicity, a cornerstone of therapeutic drug monitoring.

Correct Answer: B

Rationale: Spironolactone is a potassium-sparing diuretic that works by blocking the effects of aldosterone in the distal tubules of the kidney, leading to increased excretion of sodium and water while retaining potassium. This class of diuretics helps to conserve potassium, making them suitable for patients at risk of hypokalemia. In contrast, furosemide, hydrochlorothiazide, and bumetanide are loop diuretics, thiazide diuretics, and another loop diuretic, respectively, which all promote the loss of potassium along with sodium and water.

Correct Answer: B

Rationale: When converting a patient from IV heparin to oral warfarin (Coumadin) therapy, overlapping therapy of both medications for at least 5 days is typically recommended. This overlap ensures that the patient's blood remains appropriately anticoagulated during the transition period. The effectiveness of warfarin is delayed and it takes time for the INR to reach the therapeutic range; therefore, it is important to continue the IV heparin until the INR is within the desired range. Monitoring the INR is essential to adjust the dosages of warfarin accordingly and to ensure that the patient is receiving adequate anticoagulation therapy.

Correct Answer: B

Rationale: Fluoxetine, an SSRI, treats depression but interacts with alcohol, worsening sedation or mood , indicating a teaching gap'clients must avoid it. Feeling better in weeks aligns with SSRI onset. Reporting suicidal thoughts is critical due to early risk. Morning dosing prevents insomnia. Drinking wine risks treatment failure or safety issues, critical in depression where stability is fragile. Further teaching must clarify this interaction, ensuring fluoxetine's efficacy and client well-being, making B the statement needing correction.

Correct Answer: D

Rationale: Heparin is an anticoagulant that enhances the activity of antithrombin III, a natural inhibitor of thrombin and factor Xa, to prevent clotting. The statement that it inhibits clotting by decreasing antithrombin III effects is false, as heparin actually potentiates antithrombin III, making this the incorrect option. Its oral bioavailability is negligible (not 20-30%), as it's a large polysaccharide requiring parenteral administration (e.g., IV or subcutaneous), so this is false. Heparin is highly plasma protein-bound, not low, contradicting that option. The correct statement, replaced in the fourth slot, is that heparin binds to antithrombin III, causing a conformational change that accelerates its anticoagulant effect. This mechanism is fundamental to its clinical use in thrombosis prevention, distinguishing it from oral anticoagulants like warfarin.