Tick the antibacterial drug – a quinolone derivative:

Correct Answer: B

Rationale: Step 1: Quinolone derivatives are a class of antibiotics that target bacterial DNA synthesis. Step 2: Nalidixic acid is a first-generation quinolone derivative that inhibits DNA gyrase enzyme. Step 3: Nalidixic acid is effective against gram-negative bacteria, making it an antibacterial drug. Step 4: Nitrofurantoin is a nitrofuran antibiotic, not a quinolone derivative. Step 5: Streptomycin is an aminoglycoside antibiotic that inhibits protein synthesis, not DNA synthesis. Step 6: Metronidazole is an antimicrobial drug used for anaerobic bacteria and protozoa, not a quinolone derivative.

Correct Answer: C

Rationale: The correct answer is C: Nitroglycerin. Nitroglycerin is a vasodilator that works by releasing nitric oxide, which leads to decreased platelet aggregation. This helps improve blood flow and reduce symptoms like chest pain in patients with heart conditions. Propranolol (A) is a beta-blocker that doesn't directly affect platelet aggregation. Isosorbide mononitrate (B) is a vasodilator but doesn't have a significant impact on platelet aggregation. Nifedipine (D) is a calcium channel blocker that also doesn't directly influence platelet aggregation.

Correct Answer: A

Rationale: The correct answer is A: Severe postural hypotension. Adding a third drug that decreases central sympathetic outflow (possibly a centrally acting alpha-2 adrenergic agonist) can lead to a sudden drop in blood pressure upon standing, causing postural hypotension. This occurs due to decreased sympathetic tone leading to vasodilation and reduced vascular tone. This effect is more likely to occur shortly after initiating therapy with the new drug. Choice B: Megaloblastic anemia is not a common adverse effect of drugs that decrease sympathetic outflow. Choice C: Palpitations are not typically associated with drugs that decrease sympathetic outflow. Choice D: Pronounced sedation is not a common side effect of centrally acting sympatholytic drugs.

Correct Answer: D

Rationale: In this question, the correct answer is D) Verapamil. Verapamil is a calcium channel blocker that decreases heart rate by inhibiting calcium ion influx, leading to decreased myocardial oxygen demand. This effect helps in the treatment of angina by reducing the workload of the heart and preventing vasospastic angina attacks. Option A) Isosorbide dinitrate and option C) Nitroglycerin are nitrates that primarily work by dilating blood vessels to increase oxygen supply to the heart muscle. While they are effective in treating angina, they do not consistently decrease heart rate like verapamil. Option B) Nifedipine is a calcium channel blocker like verapamil, but it mainly acts on the peripheral vasculature to reduce blood pressure and coronary vasospasm. It does not have as significant an effect on heart rate as verapamil. Educationally, understanding the mechanisms of action of different cardiovascular drugs is crucial for prescribing the most appropriate treatment for patients with angina. Verapamil's specific effect on heart rate makes it a suitable choice for patients with angina who also require heart rate control. This knowledge helps healthcare providers tailor treatment plans to individual patient needs effectively.

Correct Answer: D

Rationale: Quinidine, a class I antiarrhythmic drug, is primarily used for preventing recurrences of atrial and ventricular extrasystoles and tachycardias. This is because quinidine works by blocking sodium channels in cardiac cells, which helps to stabilize the heart's electrical activity and prevent abnormal rhythms. Option A, converting atrial fibrillation to sinus rhythm, is not the primary use of quinidine. Drugs like amiodarone are more commonly used for this purpose due to their efficacy and safety profile. Option B, controlling ventricular rate in atrial flutter, is typically managed with drugs like beta-blockers or calcium channel blockers, which are more effective in controlling heart rate in atrial flutter. Option C, terminating ventricular tachycardia, is usually handled with antiarrhythmic medications like procainamide or amiodarone, as these are more effective in quickly terminating ventricular tachycardia. In an educational context, understanding the specific indications of each cardiovascular drug is crucial for effective pharmacological management of cardiac arrhythmias. Knowing the primary uses of medications like quinidine helps healthcare professionals make informed decisions in selecting the most appropriate treatment for their patients based on the type of arrhythmia present.