Systemic clearance (CLs) is related with:

Correct Answer: C

Rationale: Systemic clearance (CLs) is related to the volume of distribution, half-life, and elimination rate constant. CLs represents the efficiency of elimination of a drug from the body and is calculated as the rate of drug elimination divided by the plasma concentration. The volume of distribution influences the initial concentration of the drug in the body, half-life determines the time taken for the drug concentration to decrease by half, and the elimination rate constant reflects the rate at which the drug is removed from the body. Therefore, these parameters directly impact systemic clearance. Choices A, B, and D do not encompass all the essential factors that contribute to systemic clearance, making them incorrect options.

Correct Answer: C

Rationale: The correct answer is C because pilocarpine actually increases secretory and motor activity of the gut. This is due to its parasympathomimetic effects on muscarinic receptors in the gastrointestinal tract. Choices A, B, and D are correct because pilocarpine is indeed a tertiary amine alkaloid, causes miosis and decreases intraocular pressure, and is used in the treatment of glaucoma due to its ability to increase aqueous humor outflow.

Correct Answer: A

Rationale: The correct answer is A: Neostigmine. Neostigmine is a cholinesterase inhibitor that increases the levels of acetylcholine, helping counteract antimuscarinic effects. By inhibiting the breakdown of acetylcholine, neostigmine enhances cholinergic transmission, thereby reversing the antimuscarinic effects. Summary: - B: Hexametonium is a ganglionic blocker used to reduce sympathetic activity, not to treat antimuscarinic effects. - C: Homatropine is an anticholinergic drug that would exacerbate antimuscarinic effects, not treat them. - D: Acetylcholine itself would not be effective in treating antimuscarinic effects as it would be rapidly degraded by acetylcholinesterase.

Correct Answer: B

Rationale: Beta1 receptor stimulation primarily affects the heart. Stimulation leads to increased contractility, tachycardia, and increased conduction velocity in the atrioventricular node. However, bronchodilation is not a direct effect of beta1 receptor stimulation. Beta2 receptors are responsible for bronchodilation, not beta1 receptors. Therefore, choice B is incorrect. Choices A, C, and D are all correct effects of beta1 receptor stimulation.

Correct Answer: D

Rationale: The correct answer is D: Phentolamine. Phentolamine is an imidazoline derivative and a potent competitive antagonist at both alpha1 and alpha2 receptors. It blocks the effects of norepinephrine at these receptors. Prazosin (A) is an alpha1 antagonist, Labetalol (B) is a non-selective alpha and beta blocker, and Phenoxybenzamine (C) is a non-selective irreversible alpha blocker. Therefore, Phentolamine is the only drug that fits the description provided in the question.