Toxicities of H₁ antihistamines include which one of the following?

Correct Answer: D

Rationale: In the context of pharmacology, the correct answer to the question about the toxicities of H₁ antihistamines being P450 inhibition is crucial to understand. Histamine is broken down by the cytochrome P450 system in the liver. Inhibiting this system can lead to drug interactions and potential toxicity from accumulation of drugs metabolized through this pathway. Option A, blurred vision, is a common side effect of antihistamines due to their anticholinergic properties but not a direct toxicity. Option B, diarrhea, is not typically associated with H₁ antihistamines. Option C, orthostatic hypotension, is more commonly linked to alpha-1 adrenergic blockers rather than H₁ antihistamines. Educationally, this question highlights the importance of understanding the specific mechanisms of action and potential side effects of different drug classes. It emphasizes the need for healthcare professionals to be aware of the potential for drug interactions and toxicities when prescribing medications that can inhibit important metabolic pathways like the cytochrome P450 system. This knowledge is essential for safe and effective pharmacological practice.

Correct Answer: A

Rationale: In the context of pharmacology and respiratory drugs, understanding the mechanism of allergen-mediated asthma is crucial for effective treatment. The correct answer to the question is A) Increased release of mediators from mast cells. This is because allergens trigger an immune response, leading to the activation of mast cells which release inflammatory mediators like histamine, leukotrienes, and prostaglandins. These mediators cause bronchoconstriction, mucus production, and airway inflammation, resulting in the symptoms of asthma. Option B) Increased adrenergic responsiveness of the airways is incorrect because in asthma, there is actually a decrease in adrenergic responsiveness due to desensitization of beta-2 adrenergic receptors. Option C) Increased vascular permeability of bronchial tissue is incorrect as the primary pathology in asthma is related to airway inflammation and smooth muscle constriction rather than vascular changes. Option D) Decreased calcium influx into the mast cell is incorrect because mast cell degranulation, which releases inflammatory mediators, requires an influx of calcium. Educationally, understanding the pathophysiology of allergen-mediated asthma and the role of mast cells in mediating the inflammatory response helps pharmacology students comprehend the rationale behind using medications like antihistamines, leukotriene inhibitors, and corticosteroids to manage asthma symptoms effectively. This knowledge is essential for making informed clinical decisions when treating patients with respiratory conditions.

Correct Answer: D

Rationale: Terbutaline, a commonly used bronchodilator, exhibits a preference for stimulating Beta 2 receptors. This preference is crucial in pharmacology as Beta 2 receptors are primarily located in the smooth muscle of the bronchioles. Activation of Beta 2 receptors leads to bronchodilation, making it an effective treatment for conditions like asthma and COPD. Choosing option D, Beta 2, as the correct answer is supported by the pharmacological mechanism of action of terbutaline. Stimulating Beta 2 receptors causes relaxation of bronchial smooth muscle, leading to improved airway patency and increased airflow. Option A, Alpha receptors, are not the preferred target for terbutaline. Alpha receptor stimulation would not result in the desired bronchodilatory effect but may lead to vasoconstriction. Option B, Gamma receptors, are not directly involved in bronchodilation. Gamma receptors are more associated with neural processes rather than respiratory smooth muscle function. Option C, Beta 1 receptors, are primarily found in the heart and play a role in cardiac function. Stimulation of Beta 1 receptors can lead to increased heart rate and contractility but is not the target for bronchodilation with terbutaline. Understanding the specific receptor preferences of drugs is essential in pharmacology to predict their effects and potential side effects accurately. This knowledge helps healthcare professionals make informed decisions when selecting medications for patients with respiratory conditions.

Correct Answer: D

Rationale: In this pharmacology quiz question, the correct answer is D) Ratio of H₁:H₂ blockade produced by the drug. The capacity of an antihistaminic to produce sedation is influenced by the selectivity of the drug for H₁ receptors over H₂ receptors. Antihistamines that have a higher ratio of H₁ blockade to H₂ blockade are more likely to cause sedation due to their actions on the central nervous system. Option A) Relative affinity for central versus peripheral H₁ receptors is incorrect because the central versus peripheral affinity can influence the side effect profile of the drug but may not directly correlate with sedation. Option B) Ability to penetrate the blood-brain barrier is incorrect because while this is important for central nervous system effects, it is not the sole determinant of sedation. Option C) Individual susceptibility is incorrect as it refers to variations in response among individuals but does not directly explain the mechanism behind sedation in antihistamines. Educationally, understanding the pharmacological basis of sedation caused by antihistamines is crucial for healthcare professionals to make informed decisions about drug selection for patients, especially those prone to sedation. It underscores the importance of considering drug properties like receptor selectivity in clinical practice to minimize adverse effects and optimize therapeutic outcomes.

Correct Answer: B

Rationale: In this question, the correct answer is B) Intestines. The smooth muscle stimulating action of 5-HT (serotonin) is most marked in the intestines. Explanation: - Serotonin is a neurotransmitter that plays a key role in gastrointestinal motility by stimulating smooth muscle contraction in the intestines. - This action of serotonin in the intestines helps in regulating peristalsis and overall gut movement. Why others are wrong: - A) Bronchi: While serotonin can also have some effect on bronchial smooth muscle, its most significant action is in the intestines. - C) Ureter: Serotonin does not have a significant impact on ureter smooth muscle contraction. - D) Biliary tract: Although serotonin can affect smooth muscle in the biliary tract to some extent, its primary action is in the intestines. Educational context: Understanding the specific actions of neurotransmitters like serotonin on different smooth muscles is crucial in pharmacology, especially when studying respiratory drugs. Knowing where serotonin exerts its effects can help in predicting potential side effects or interactions of drugs that target serotonin receptors. This knowledge is essential for healthcare professionals to make informed decisions regarding drug therapy for respiratory and gastrointestinal conditions.