The following drugs cause their primary pharmacodynamic effect via non-receptor mediated mechanisms:

Correct Answer: B

Rationale: Mannitol works osmotically, increasing urine flow without binding to receptors. Others rely on receptor or enzyme-based actions.

Correct Answer: B

Rationale: Protamine is the antidote for Heparin. Heparin is an anticoagulant medication that works by increasing the activity of antithrombin III, leading to the inhibition of clotting factors. In cases of excessive bleeding or overdose with Heparin, protamine can be administered to neutralize its anticoagulant effects. Protamine works by binding to heparin to form a stable complex, thereby reversing the anticoagulant activity of Heparin. It is important for healthcare providers to be familiar with the antidotes for various medications to manage potential complications effectively.

Correct Answer: A

Rationale: Montelukast is primarily used for the prevention and treatment of asthma. It is a leukotriene receptor antagonist that works by blocking leukotrienes, substances in the body that cause symptoms of asthma and allergic rhinitis. By blocking leukotrienes, Montelukast helps to reduce inflammation in the airways, decrease bronchoconstriction, and ultimately improve asthma symptoms and prevent asthma attacks. It is not used for lowering pain levels, treating depression, or improving wakefulness in patients.

Correct Answer: D

Rationale: Phenytoin toxicity (ataxia, nystagmus) occurs despite a ‘normal' total plasma level (15 mg/L) due to nephrotic syndrome's hypoalbuminemia. Normally, phenytoin is 90% protein-bound, with 10% free (active). Low albumin increases the free fraction (e.g., to 20%), raising CNS exposure despite a therapeutic total level. Creatinine doesn't typically interfere with phenytoin assays; they're reliable unless specific lab issues exist. Furosemide doesn't alter the blood-brain barrier for phenytoin; no evidence supports this. Oestrogen in HRT doesn't directly enhance phenytoin's CNS toxicity; it may affect metabolism, but not here. Cerebrovascular events don't fit the drug-related context. The increased free fraction explains toxicity, necessitating free level monitoring in hypoalbuminemia.

Correct Answer: A

Rationale: Finasteride, a 5-alpha reductase inhibitor, is prescribed as Proscar for benign prostatic hyperplasia (BPH) but also as Propecia for male pattern baldness, reducing dihydrotestosterone levels to slow hair loss. Without a prostate disorder, baldness becomes a plausible alternative indication. Erectile dysfunction isn't treated by finasteride-it may even cause it as a side effect-making that question irrelevant. Stomach ulcers and high blood pressure have no connection to finasteride's mechanism, which targets androgen pathways, not gastrointestinal or cardiovascular systems. Asking about baldness aligns with finasteride's dual use, probing a condition tied to its action on hair follicles, offering a logical explanation for its prescription in the absence of BPH, and guiding the nurse's understanding of the client's treatment rationale.