Nokea
Albuterol causes selective activation of β2 adrenergic receptors when administered in 'low doses,' mainly by inhalation. If very large doses of albuterol were given, or if the drug is administered intravenously, the effects caused by albuterol would look quite different and would resemble those of which one of the following drugs?
Correct Answer: B
Rationale: Step 1: Albuterol selectively activates β2 adrenergic receptors in low doses.
Step 2: Isoprenaline is a non-selective beta-adrenergic agonist.
Step 3: Very large doses of albuterol or IV administration would lead to non-selective activation of beta receptors.
Step 4: Isoprenaline also activates both β1 and β2 receptors, causing a broad range of effects.
Step 5: Therefore, the effects of high-dose albuterol would resemble those of Isoprenaline, making B the correct answer.
Summary:
Choice A (Epinephrine) is incorrect because epinephrine primarily acts on both α and β adrenergic receptors, not just β2.
Choice C (Norepinephrine) is incorrect as it mainly acts on α adrenergic receptors, not β.
Choice D (Phenylephrine) is incorrect because it is a