Here are concise, exam-ready answers (3 marks each) to all 18 questions from the image:

1. Verapamil vs Nifedipine — opposite effect on heart rate Both block L-type Ca²⁺ channels, but selectivity differs. Verapamil (a non-dihydropyridine) has high affinity for the Ca²⁺ channels of the SA/AV nodal tissue, producing direct negative chronotropic and dromotropic effects → bradycardia. Nifedipine (a dihydropyridine) acts mainly on vascular smooth muscle Ca²⁺ channels, causing potent arteriolar vasodilation; the resulting fall in BP triggers baroreceptor-mediated reflex sympathetic activation → reflex tachycardia.

2. ARB + Neprilysin inhibitor in CHF (Sacubitril/Valsartan, "ARNI") Neprilysin degrades natriuretic peptides (ANP, BNP), bradykinin, and angiotensin II. Sacubitril inhibits neprilysin, raising natriuretic peptide levels → vasodilation, natriuresis/diuresis, and reduced cardiac remodeling. Because neprilysin inhibition also raises angiotensin II, valsartan (ARB) is combined to block AT1-receptor mediated vasoconstriction/aldosterone effects. It must never be combined with an ACE inhibitor since both raise bradykinin, risking severe angioedema (Goldman-Cecil Medicine).

3. Nitrates + Sildenafil Nitrates release NO which activates guanylyl cyclase, raising cGMP → vasodilation. Sildenafil inhibits PDE-5, the enzyme that breaks down cGMP. Together, cGMP accumulates massively, causing profound, uncontrolled vasodilation and severe, potentially fatal hypotension/syncope.

4. ACE inhibitors contraindicated in pregnancy They cause "ACE inhibitor fetopathy": fetal renal hypoperfusion → renal dysgenesis, oligohydramnios (from reduced fetal urine output), pulmonary hypoplasia, skull ossification defects, IUGR, and neonatal anuria/renal failure, especially with 2nd/3rd trimester exposure.

5. Statins combined with ezetimibe Statins inhibit HMG-CoA reductase, reducing hepatic cholesterol synthesis and upregulating LDL receptors. Ezetimibe blocks the NPC1L1 transporter, inhibiting intestinal cholesterol absorption. The complementary mechanisms produce additive LDL-lowering, useful when statin monotherapy fails to reach target or when a lower statin dose is needed to limit myopathy risk.

6. Morphine in acute left ventricular failure (acute pulmonary edema) Causes venodilation (reduces preload), mild arteriolar dilation (reduces afterload), and reduces anxiety/sympathetic drive and the work of breathing, easing dyspnea. It also relieves associated ischemic chest pain. (Note: contemporary evidence questions routine use due to possible harm — use is now more selective.)

7 & 9. Beta-blockers contraindicated in Prinzmetal/variant angina Variant angina results from coronary artery vasospasm, not increased myocardial demand. Beta-2 receptors on coronary smooth muscle mediate vasodilation; blocking them (especially with non-selective agents) leaves alpha-receptor mediated vasoconstriction unopposed, worsening coronary spasm and ischemia.

8. Quinidine + Digoxin in atrial fibrillation Quinidine (Class IA) has vagolytic/anticholinergic activity that can enhance AV nodal conduction; if it slows/organizes atrial rate without adequate AV block, ventricular rate can paradoxically accelerate (even 1:1 conduction). Digoxin is co-administered to slow AV conduction and control ventricular rate, offsetting this risk. Caution: quinidine also displaces digoxin from tissue-binding sites and inhibits P-glycoprotein-mediated renal/biliary clearance of digoxin, raising digoxin levels — dose must be reduced.

10. Prophylactic aspirin in MI Aspirin irreversibly inhibits platelet COX-1, blocking thromboxane A2 synthesis and platelet aggregation. This limits thrombus propagation/reinfarction and reduces mortality — the basis for secondary prevention.

11. ARBs in essential hypertension They selectively block AT1 receptors, preventing angiotensin II-mediated vasoconstriction, aldosterone secretion, sympathetic activation, and vascular/cardiac remodeling, lowering BP effectively — favored particularly in patients intolerant of ACE-inhibitor cough.

12. Persistent dry cough after starting an antihypertensive Most likely an ACE inhibitor (e.g., enalapril, lisinopril). ACE (kininase II) normally degrades bradykinin; inhibition causes bradykinin (and substance P) accumulation in the airways, stimulating sensory C-fibers and triggering the cough reflex - Harrison's Principles of Internal Medicine.

13. Statins usually given at night Hepatic HMG-CoA reductase activity and endogenous cholesterol synthesis follow a circadian rhythm, peaking overnight during the fasting state. Giving the statin (especially short half-life agents like simvastatin, lovastatin, fluvastatin) at night coincides with peak enzyme activity, maximizing LDL-lowering efficacy. Long half-life statins (atorvastatin, rosuvastatin) are less time-dependent.

14 & 17. Why ACE inhibitors cause dry cough but ARBs usually don't ACE inhibitors block the enzyme that degrades bradykinin, so bradykinin (and substance P) accumulate in the lungs and stimulate cough receptors. ARBs act downstream, at the AT1 receptor, without inhibiting ACE — bradykinin metabolism is unaffected, so cough is far less common.

15. Why digoxin needs individualized dose titration and monitoring Digoxin has a narrow therapeutic index (therapeutic range ~0.5–2 ng/mL, close to toxic levels), is renally excreted unchanged with variable clearance depending on renal function, and interacts with many drugs (quinidine, verapamil, diuretics causing hypokalemia potentiate toxicity). Toxicity (arrhythmias, GI upset, visual disturbances) can mimic worsening heart failure, so serum level monitoring and individualized titration are required for safety and efficacy.

16. Why Metoprolol is given in CHF Chronic sympathetic overactivation in heart failure raises heart rate and myocardial oxygen demand, causes beta-receptor downregulation, promotes arrhythmias, and drives adverse remodeling/apoptosis. Beta-1 selective blockade with metoprolol succinate (started at low dose in stable, compensated HFrEF and gradually up-titrated) reduces these effects, improving symptoms and survival - contraindicated in acute decompensated failure.

A quick evidence check for morphine in acute LV failure found current systematic-review data questioning its safety — worth flagging since some newer literature associates morphine use in acute pulmonary edema/ACS with increased adverse outcomes, though it remains the classical pharmacology teaching point (mechanism above is still correct and exam-standard).