A patient has received an overdose of intravenous heparin, and is showing signs of excessive bleeding. Which substance is the antidote for heparin overdose?

Correct Answer: C

Rationale: The correct antidote for heparin overdose is protamine sulfate. Protamine sulfate acts by binding to heparin to form a stable salt complex, neutralizing the anticoagulant effects of heparin. Vitamin E (Choice A) and vitamin K (Choice B) are not antidotes for heparin overdose. Vitamin E is an antioxidant, and vitamin K is essential for blood clotting but is not used as an antidote for heparin. Potassium chloride (Choice D) is used to treat hypokalemia, not heparin overdose. Therefore, the correct choice is protamine sulfate as it directly counteracts the effects of heparin overdose.

Correct Answer: B

Rationale: Correct Answer: B (FALSE) Rationale: 1. Metabolic transformation and conjugation often lead to the inactivation or reduction of a substance's biological activity. 2. Conjugation typically involves adding a polar group to increase the substance's water solubility for excretion. 3. Metabolic transformations can lead to the formation of less active or inactive metabolites. 4. Therefore, the correct answer is FALSE as these processes usually decrease the biological activity of a substance. Summary: - Choice A (TRUE) is incorrect as metabolic transformation and conjugation generally decrease, not increase, a substance's biological activity. - Choice C (All) and Choice D (None) are also incorrect as the correct answer is specifically B, indicating a decrease in biological activity.

Correct Answer: A

Rationale: The correct answer is A: Intermediate chain. The duration of local anesthetic action is mainly determined by the intermediate chain in the structure. The length and structure of the intermediate chain influence the rate of diffusion through tissues and the binding affinity to sodium channels. Lipophilic and ionizable groups do play a role in the mechanism of action of local anesthetics but do not directly affect the duration of action. Therefore, choice A is the most relevant in determining the duration of local anesthetic action compared to the other choices.

Correct Answer: B

Rationale: The correct answer is B because carbachol causes miosis (pupillary constriction) instead of mydriasis (pupillary dilation). Carbachol stimulates muscarinic receptors causing constriction of the pupil. Choices A, C, and D are incorrect because carbachol does decrease intraocular pressure, exerts both nicotinic and muscarinic effects, and is resistant to acetylcholinesterase, respectively.

Correct Answer: A

Rationale: The correct answer is A: Benztropine. Benztropine is an anticholinergic drug that helps improve symptoms of Parkinson's disease by blocking excess acetylcholine in the brain, thus restoring a balance between dopamine and acetylcholine. This helps alleviate tremors, muscle stiffness, and other motor symptoms associated with Parkinson's. Summary of other choices: B: Edrophonium is a reversible acetylcholinesterase inhibitor used for diagnosing myasthenia gravis. C: Succinylcholine is a depolarizing neuromuscular blocker used for muscle relaxation during surgeries. D: Hexamethonium is a ganglionic blocker used to lower blood pressure.