Indicate the drug which is a leucotriene receptor antagonist:

Correct Answer: B

Rationale: The correct answer is B: Zafirlucast, a leucotriene receptor antagonist. Leukotrienes are inflammatory mediators in asthma. Zafirlucast specifically blocks the action of leukotrienes by binding to their receptors, reducing inflammation and bronchoconstriction. Sodium cromoglycate (A) is a mast cell stabilizer, not a leukotriene receptor antagonist. Zileutin (C) inhibits 5-lipoxygenase, an enzyme involved in leukotriene synthesis. Triamcinolone (D) is a corticosteroid that acts through a different anti-inflammatory mechanism.

Correct Answer: A

Rationale: Step 1: Class IC antiarrhythmic drugs work by blocking sodium channels to slow down conduction in the heart. Step 2: Flecainide is a Class IC antiarrhythmic drug that specifically blocks sodium channels effectively. Step 3: Sotalol (Choice B) is a Class III antiarrhythmic drug that blocks potassium channels. Step 4: Lidocaine (Choice C) is a Class IB antiarrhythmic drug that also blocks sodium channels, but it is not a Class IC drug. Step 5: Verapamil (Choice D) is a calcium channel blocker and not a Class IC antiarrhythmic drug. Summary: Flecainide (Choice A) is the correct answer as it is a Class IC antiarrhythmic drug that blocks sodium channels, while the other choices are different classes of antiarrhythmics with different mechanisms of action.

Correct Answer: C

Rationale: The correct answer is C: Guanethidine. Guanethidine is a sympatholytic drug that blocks the release of norepinephrine from sympathetic nerve terminals, thus reducing sympathetic activity. This leads to a decrease in blood pressure. A: Labetalol is a non-selective beta blocker with alpha-blocking activity. B: Prazosin is an alpha-1 adrenergic receptor antagonist. D: Clonidine is a centrally acting alpha-2 adrenergic agonist. Therefore, the correct choice for a sympatholytic drug is Guanethidine due to its mechanism of action in inhibiting sympathetic activity.

Correct Answer: C

Rationale: The correct answer is C: Dysfunction of regulation of cerebral vessel tonus. Migraine is a neurological disorder characterized by recurrent headaches. The underlying cause is believed to involve abnormal brain activity and the dysfunction of regulating cerebral vessel tonus, leading to vasodilation and inflammation. Thrombosis of cerebral vessels (choice A), brain hemorrhage (choice B), and malignant growth in the brain (choice D) are not directly associated with the pathophysiology of migraine.

Correct Answer: C

Rationale: The correct answer is C: Crystalline insulin. Diabetic coma is a severe complication of diabetes characterized by extremely high blood sugar levels. Administration of crystalline insulin helps lower blood sugar rapidly. Lente insulin (A) is not fast-acting enough for diabetic coma treatment. Glucose (B) would further elevate blood sugar levels. Oral anti-diabetic drugs (D) are not suitable for immediate treatment of diabetic coma.