A 75-year-old female with asthma is prescribed montelukast. Montelukast works by:

Correct Answer: C

Rationale: The correct answer is C: Blocking leukotriene receptors in the lungs. Montelukast is a leukotriene receptor antagonist, specifically targeting the cysteinyl leukotriene receptor, to reduce inflammation, bronchoconstriction, and mucus production in asthma. This mechanism helps in preventing asthma symptoms and attacks. Choice A is incorrect because blocking beta-2 adrenergic receptors would lead to bronchoconstriction and worsen asthma symptoms. Choice B is incorrect as histamine release is not the main target of montelukast. Choice D is also incorrect as stimulating acetylcholine release would not help in managing asthma and would likely exacerbate symptoms.

Correct Answer: C

Rationale: Rationale: 1. Sitagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor. 2. DPP-4 enzyme breaks down incretin hormones like GLP-1. 3. By inhibiting DPP-4, sitagliptin increases incretin hormone levels. 4. Incretin hormones stimulate insulin release and inhibit glucagon. 5. Thus, sitagliptin indirectly increases insulin secretion. Summary: A: Incorrect - Sitagliptin indirectly increases insulin secretion. B: Incorrect - Sitagliptin does not affect glucose absorption. D: Incorrect - Sitagliptin does not increase renal glucose excretion.

Correct Answer: C

Rationale: The correct answer is C: Peripheral edema. Calcium channel blockers cause vasodilation leading to fluid accumulation in the peripheral tissues, resulting in peripheral edema. Dry mouth (A) and coughing (B) are more commonly associated with other medications like antihistamines and ACE inhibitors. Bradycardia (D) is a potential side effect of calcium channel blockers but is less common than peripheral edema.

Correct Answer: B

Rationale: The correct answer is B: Beta-adrenergic receptors. Albuterol is a beta-2 adrenergic agonist that works by binding to beta-2 adrenergic receptors in the airway smooth muscle, leading to bronchodilation. This mechanism helps in treating conditions like asthma and COPD. Choice A (Alpha-adrenergic receptors) is incorrect because albuterol specifically targets beta-adrenergic receptors, not alpha-adrenergic receptors. Choice C (Cholinergic receptors) is incorrect because albuterol does not directly interact with cholinergic receptors. Choice D (Dopaminergic receptors) is incorrect as albuterol does not have a significant affinity for dopaminergic receptors. In conclusion, the correct answer is B because albuterol's mechanism of action involves activating beta-adrenergic receptors to produce bronchodilation.

Correct Answer: B

Rationale: The correct answer is B: Inhibiting HMG-CoA reductase. Simvastatin is a statin medication that works by inhibiting the enzyme HMG-CoA reductase, which is involved in the synthesis of cholesterol in the liver. By inhibiting this enzyme, simvastatin reduces the production of cholesterol in the body, leading to lower LDL cholesterol levels. Choice A is incorrect because simvastatin actually decreases LDL cholesterol levels. Choice C is incorrect as blocking cholesterol absorption in the intestine is the mechanism of action for a different class of drugs called bile acid sequestrants. Choice D is incorrect as simvastatin primarily reduces LDL cholesterol levels and has a modest effect on increasing HDL cholesterol levels.