A patient presents with food poisoning that is attributed to botulism (Botulinum toxin poisoning). Which of the following is a correct characteristic, finding, or mechanism associated with this toxin?

Correct Answer: A

Rationale: The correct answer is A: Complete failure of all cholinergic neurotransmission. Botulinum toxin inhibits acetylcholine release at neuromuscular junctions, leading to complete failure of all cholinergic neurotransmission. This results in flaccid paralysis and characteristic symptoms of botulism. Choice B is incorrect because pralidoxime is used to treat organophosphate poisoning, not botulism. Choice C is incorrect as botulinum toxin affects both parasympathetic and sympathetic nervous systems. Choice D is incorrect as botulinum toxin does not cause overstimulation but rather inhibits neurotransmission.

Correct Answer: B

Rationale: The correct answer is B. Pirenzepine is NOT preferred over propantheline in the treatment of intestinal colic because pirenzepine is a selective M1 receptor antagonist used for peptic ulcer disease, while propantheline is an anticholinergic used for GI spasms. Choice A is incorrect because atropine is preferred over hyoscine in thyrotoxic patients due to its faster onset. Choice C is incorrect because ipratropium is not necessarily better than atropine in bronchial asthma as they have different mechanisms of action. Choice D is incorrect because atropine is actually preferred over tropicamide for fundus examination due to its longer duration of action.

Correct Answer: D

Rationale: The correct answer is D: Hydrolysis by cholinesterase enzyme. Acetylcholine is broken down by cholinesterase enzyme into choline and acetate, leading to the termination of its action. Rapid hepatic metabolism (A) is not the primary mechanism for acetylcholine breakdown. Reuptake by nerve endings (B) refers to reuptake of neurotransmitters, not breakdown. Binding to plasma proteins (C) does not affect the duration of acetylcholine action.

Correct Answer: D

Rationale: Hyoscine, also known as scopolamine, is an anticholinergic drug that acts by blocking muscarinic receptors. It produces sedation by crossing the blood-brain barrier and affecting the central nervous system. Its antiemetic action is due to its ability to inhibit the vomiting center in the brain. Stimulation of the respiratory center is not a typical action of hyoscine. Lastly, hyoscine decreases salivary secretion due to its anticholinergic effects. Therefore, the correct answer is D (Increase of salivary secretion) as it is inconsistent with the pharmacological actions of hyoscine.

Correct Answer: A

Rationale: The correct answer is A: Eating seeds containing atropine. Atropine is a plant alkaloid commonly found in certain seeds that can cause symptoms such as fever, skin flush, dry mouth, constipation, dilated pupils, and increased heart rate when ingested. Atropine is known to have anticholinergic effects, which align with the symptoms presented by the child. Malathion (B) is an insecticide that typically causes different symptoms like nausea, vomiting, and diarrhea. Echothiophate drops (C) are cholinesterase inhibitors used in the treatment of glaucoma, which would not produce the described symptoms. Physostigmine (D) is a cholinesterase inhibitor that would not cause symptoms of anticholinergic toxicity seen in the child.