Nokea
Which of the following drugs has muscarinic and nicotinic actions and is resistant to hydrolysis by both true and pseudo cholinesterase:
- A. Acetylcholine
- B. Carbachol
- C. Bethanechol
- D. Succinylcholine
Correct Answer: B
Rationale: Step-by-step rationale for why B (Carbachol) is the correct answer:
1. Carbachol is a cholinergic drug that acts on both muscarinic and nicotinic receptors.
2. It is resistant to hydrolysis by both true and pseudo cholinesterase enzymes.
3. Acetylcholine (A) is rapidly hydrolyzed by both cholinesterases.
4. Bethanechol (C) is a muscarinic agonist but not a nicotinic agonist.
5. Succinylcholine (D) is a depolarizing neuromuscular blocking agent, not a cholinergic agonist.
Summary:
Carbachol is the only drug among the choices that has both muscarinic and nicotinic actions and is resistant to hydrolysis by cholinesterases. Acetylcholine is rapidly hydrolyzed, Bethanechol does not have nicotinic actions, and Succinyl
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The person with _____ is most likely to receive insulin therapy.
- A. myxedema
- B. Graves’ disease
- C. diabetes insipidus
- D. hyperglycemia
Correct Answer: D
Rationale: The correct answer is D: hyperglycemia. Hyperglycemia refers to high blood sugar levels, a hallmark of diabetes mellitus. Insulin therapy is commonly prescribed to individuals with diabetes to help regulate their blood sugar levels. Myxedema (choice A) is associated with hypothyroidism, Graves' disease (choice B) is an autoimmune disorder affecting the thyroid, and diabetes insipidus (choice C) involves the kidneys and has no direct relation to insulin therapy for diabetes. Therefore, hyperglycemia is the most appropriate condition for receiving insulin therapy.
In the adrenal medulla:
- A. epinephrine is formed by the hydroxylation and decarboxylation of tyrosine
- B. 10% of the cells are the epinephrine-secreting type
- C. plasma norepinephrine levels are generally unchanged after adrenalectomy
- D. catecholamine t1/2 is 10 minutes in the circulation
Correct Answer: C
Rationale: Rationale for Choice C: Plasma norepinephrine levels are generally unchanged after adrenalectomy in the adrenal medulla because norepinephrine is mainly produced by postganglionic sympathetic nerve endings rather than the adrenal medulla. Adrenalectomy removes the adrenal gland, which primarily secretes epinephrine, not norepinephrine. Therefore, plasma norepinephrine levels would not be significantly affected by adrenalectomy.
Summary of other choices:
A: Incorrect. Epinephrine is formed from norepinephrine, not tyrosine, through methylation and hydroxylation.
B: Incorrect. The majority of cells in the adrenal medulla are epinephrine-secreting cells, not just 10%.
D: Incorrect. The half-life of catecholamines in the circulation is very short, around 2 minutes, not 10 minutes.
Which one of the following properties makes labetalol different from nearly all the other β-blockers on the market?
- A. Also blocks alpha-adrenergic receptors
- B. Causes strong atropine-like side effects, has same side effects as atropine
- C. Only blocks β1 receptors
- D. Safe for asthmatics because it lacks β2 blocking activity
Correct Answer: A
Rationale: The correct answer is A because labetalol is unique among most β-blockers as it also blocks alpha-adrenergic receptors. This dual action results in vasodilation and reduced blood pressure. Choice B is incorrect as labetalol does not cause atropine-like side effects. Choice C is incorrect as labetalol blocks both β1 and β2 receptors. Choice D is also incorrect as labetalol does have some β2 blocking activity, making it not entirely safe for asthmatics.
Concerning Alpha blockers, which of the following is CORRECT:
- A. Phentolamine is a selective Alpha1 blocker
- B. Alpha2 blockers decrease noradrenaline release
- C. Prazosin can block Alpha1 receptor only
- D. They decrease both BP and HR
Correct Answer: C
Rationale: Rationale:
C: Prazosin can block Alpha1 receptor only.
- Prazosin is a selective Alpha1 blocker, mainly used for hypertension.
- By blocking Alpha1 receptors, it reduces vasoconstriction and lowers blood pressure.
- Prazosin does not affect Alpha2 receptors, distinguishing it from non-selective Alpha blockers.
- Correct as it accurately describes Prazosin's mechanism of action.
Incorrect:
A: Phentolamine is a non-selective Alpha blocker, affecting both Alpha1 and Alpha2 receptors.
B: Alpha2 blockers increase noradrenaline release by inhibiting the negative feedback control.
D: Alpha blockers typically decrease blood pressure, but can increase heart rate due to vasodilation.
Enlargement of the thyroid gland:
- A. is called a goiter.
- B. causes Addisonian crisis.
- C. makes a person appear cushingoid.
- D. causes hypocalcemic tetany.
Correct Answer: A
Rationale: Step-by-step rationale for why choice A is correct:
1. Enlargement of the thyroid gland is known as a goiter.
2. A goiter can result from various conditions like iodine deficiency or thyroid disorders.
3. It is a common sign of thyroid dysfunction.
4. Goiter may or may not cause symptoms depending on the underlying cause.
5. Therefore, choice A is the correct answer.
Summary:
- Choice B (Addisonian crisis) is incorrect as it is associated with adrenal insufficiency, not thyroid enlargement.
- Choice C (cushingoid appearance) is incorrect as it is related to excess cortisol production, not thyroid enlargement.
- Choice D (hypocalcemic tetany) is incorrect as it is due to low calcium levels, not thyroid enlargement.