A patient with asthma is prescribed salmeterol. Salmeterol works primarily by:

Correct Answer: B

Rationale: The correct answer is B: Relaxing bronchial smooth muscle by stimulating beta-2 adrenergic receptors. Salmeterol is a long-acting beta-2 agonist that works by binding to beta-2 adrenergic receptors in the lungs, leading to the relaxation of bronchial smooth muscle. This results in bronchodilation, which helps in relieving asthma symptoms. Choice A is incorrect as salmeterol does not block the action of histamine. Choice C is incorrect as salmeterol does not inhibit the release of leukotrienes. Choice D is incorrect as salmeterol does not block acetylcholine receptors in the lungs. In summary, the correct answer B is based on the mechanism of action of salmeterol as a beta-2 adrenergic receptor agonist, leading to bronchodilation and improved breathing in asthma patients.

Correct Answer: B

Rationale: The correct answer is B: Dilating the bronchioles. Albuterol is a beta-2 adrenergic agonist that acts on bronchial smooth muscle to cause bronchodilation, improving airflow in patients with COPD. This effect helps relieve symptoms of bronchoconstriction and shortness of breath. Choices A, C, and D are incorrect because albuterol does not increase mucus production, decrease bronchial inflammation, or inhibit histamine release. It primarily targets bronchial smooth muscle to promote bronchodilation.

Correct Answer: B

Rationale: The therapeutic index value of 2 indicates that the toxic dose is 2 times the effective dose. To have a 50% chance of developing toxic side effects, the patient would need to take a dose that is half of the toxic dose. This means the patient would need to take 1/2 of the toxic dose at each administration. Since the therapeutic index is 2, the patient would need to divide the toxic dose into 2 equal parts, which results in 2 doses. Therefore, the correct answer is B: Two doses. Summary: A: Incorrect - Taking one dose would exceed the therapeutic index and increase the risk of toxic side effects. C: Incorrect - Not providing a clear answer. D: Incorrect - Incomplete option.

Correct Answer: A

Rationale: The correct answer is A: Cyproheptadine. Cyproheptadine is a histamine and serotonin receptor antagonist, making it suitable for treating intestinal hypermobility of carcinoid tumors. Histamine and serotonin play a role in intestinal motility, and blocking their receptors can help alleviate symptoms. Summary of other choices: B: Ergonovine is a uterine stimulant and is not indicated for treating intestinal hypermobility. C: Loratadine is a selective histamine H1 receptor antagonist used for allergies, not for intestinal hypermobility. D: Promethazine is an antihistamine and antiemetic, but it is not commonly used for treating intestinal hypermobility associated with carcinoid tumors.

Correct Answer: A

Rationale: The correct answer is A: Reversible binding to H1 receptors. Antihistamines work by competitively binding to H1 receptors, blocking the action of histamine. This reversible binding prevents histamine from exerting its effects, such as inflammation and itching. Choice B is incorrect because irreversible binding would lead to prolonged effects and potential toxicity. Choice C is incorrect as H2 receptors are targeted by a different class of drugs used for conditions like acid reflux. Choice D is also incorrect for the same reason as choice B.