Pharmacodynamics involves the study of following EXCEPT:

Correct Answer: B

Rationale: Pharmacodynamics specifically focuses on how drugs interact with the body to produce their effects, including mechanisms of drug action and biological/therapeutic effects. Absorption and distribution of drugs fall under pharmacokinetics, not pharmacodynamics. Therefore, choice B is the correct answer. Absorption and distribution are crucial in determining drug concentrations at the site of action, but they do not directly relate to the study of how drugs exert their effects on the body. Choices A, C, and D are incorrect as they are all aspects that are studied within pharmacodynamics.

Correct Answer: A

Rationale: Rationale: A is correct because lobeline is a plant derivative found in Lobelia plants, acting as a cholinomimetic with lower potency than nicotine but similar action spectrum. Nicotine is a potent cholinomimetic derived from tobacco. Pilocarpine is a cholinomimetic derived from the Pilocarpus shrub with different actions. Carbachol is a synthetic cholinomimetic with different properties. Acetylcholine is a neurotransmitter, not a plant-derived cholinomimetic.

Correct Answer: C

Rationale: The correct answer is C: Bronchial asthma. Antimuscarinic drugs can worsen bronchial asthma due to their potential to cause bronchoconstriction. Glaucoma (A), myasthenia (B), and paralytic ileus/urinary bladder atony (D) are contraindications for antimuscarinic drugs due to their exacerbation of symptoms in these conditions. Glaucoma can worsen due to increased intraocular pressure, myasthenia can lead to muscle weakness, and antimuscarinic drugs can further inhibit bowel and bladder function in paralytic ileus and urinary bladder atony.

Correct Answer: D

Rationale: Beta2 receptor stimulation primarily leads to vasodilation, bronchodilation, and relaxation of smooth muscles in non-cardiac tissues. It does not cause tachycardia, which is primarily mediated by Beta1 receptor stimulation. Therefore, option D is the correct answer. Option A is incorrect because Beta2 stimulation does not stimulate renin secretion. Option B is incorrect as Beta2 stimulation increases potassium concentration in plasma. Option C is incorrect as Beta2 stimulation causes relaxation of bladder and uterus muscles.

Correct Answer: B

Rationale: The correct answer is B: Stimulation of responses to serotonin. Phentolamine is an alpha-adrenergic blocker, causing vasodilation and reducing peripheral resistance (A). It can lead to tachycardia (C) due to its vasodilatory effects. Phentolamine does not stimulate muscarinic H1 and H2 histamine receptors (D). Serotonin receptors are not affected by phentolamine, making choice B the correct answer.