In passive diffusion, drugs are transported across the membrane via

Correct Answer: A

Rationale: Passive diffusion involves movement of drug molecules across the cell membrane lipid layer from an area of high concentration to low concentration, without the need for energy or carrier proteins. Lipid-soluble drugs can easily diffuse through the lipid bilayer due to their hydrophobic nature. This process is driven by the concentration gradient and follows Fick's law of diffusion. Ion channels (B) facilitate the movement of ions, not drugs. Methyl residues (C) and transport proteins (D) are not directly involved in passive diffusion of drugs.

Correct Answer: C

Rationale: Certainly! Prazosin is an alpha-1 antagonist, which means it blocks the activation of alpha-1 adrenergic receptors. By blocking these receptors, prazosin leads to vasodilation and reduced peripheral vascular resistance, ultimately lowering blood pressure. The other options are not correct because prazosin does not act as a beta-1 antagonist (B), beta-2 agonist (D), or alpha-1 agonist (A) in the context of treating hypertension.

Correct Answer: B

Rationale: The correct answer is B: Increase of bronchial secretion. Parasympathetic stimulation activates the vagus nerve, leading to bronchial smooth muscle relaxation and increased secretion to facilitate breathing. This response helps in clearing the airways and optimizing gas exchange. Choices A, C, and D are incorrect because parasympathetic stimulation typically does not lead to an increase in intestinal motility (A), contraction of the iris sphincter muscle causing miosis (C), or a decrease in heart rate (D), as these are more characteristic of sympathetic stimulation.

Correct Answer: A

Rationale: Step 1: Nicotinic AChRs are ion channels that allow the passage of ions across the cell membrane in response to acetylcholine. Step 2: The ion channels are not protein-bound or slow, so option B is incorrect. Step 3: Nicotinic AChRs are not G-coupled receptors, so option C is incorrect. Step 4: Nicotinic AChRs are located on the cell membrane, making them water-soluble, so option A is correct. Step 5: Nicotinic AChRs are not intracellular receptors, so option D is incorrect.

Correct Answer: C

Rationale: In pharmacology, understanding the absorption of drugs is crucial for predicting their efficacy and potential side effects. In the case of hydrochlorothiazide, a diuretic commonly used to treat hypertension, its main site of absorption is the small intestine. The small intestine is the primary site of drug absorption in the digestive tract due to its large surface area, which is ideal for efficient absorption of hydrophilic drugs like hydrochlorothiazide. The presence of villi and microvilli further increases the absorptive surface area, allowing for better drug uptake into the bloodstream. Option A, the oral mucosa, is not the main site of absorption for hydrochlorothiazide as it is primarily absorbed in the gastrointestinal tract. The stomach (Option B) is not an ideal site for drug absorption due to its acidic environment and limited surface area compared to the small intestine. The colon (Option D) is mainly responsible for water and electrolyte absorption rather than drug absorption. Educationally, understanding the specific absorption sites of drugs in the digestive tract is essential for pharmacology students and healthcare professionals to optimize drug therapy and anticipate potential drug interactions or variations in drug effects based on the route of administration. This knowledge enhances clinical decision-making and patient care outcomes.