A patient has allergies and takes an antihistamine. The patient wants to know how the drug works. The nurse understands that antihistamines work because they are what?
Antidotes
Antagonists
Agonists
Activators
The Correct Answer is B
Choice A reason: Antidotes counteract specific toxins or drugs (e.g., naloxone for opioids). Antihistamines don’t neutralize allergens but block histamine receptors to reduce allergic symptoms like itching or sneezing. They target H1 or H2 receptors, not a toxin, making this choice incorrect for describing antihistamine mechanism of action.
Choice B reason: Antihistamines are antagonists, binding to histamine receptors (H1 or H2) without activating them, preventing histamine from triggering allergic responses like vasodilation or bronchoconstriction. This competitive inhibition reduces symptoms such as itching, sneezing, or gastric acid secretion, making this the correct choice for their pharmacological action.
Choice C reason: Agonists activate receptors to produce a response. Antihistamines block histamine receptors, not activate them, preventing allergic effects. Acting as agonists would mimic histamine, worsening symptoms like swelling or itching, which is opposite to their therapeutic role, making this choice incorrect.
Choice D reason: Activators is a vague term not used in pharmacology to describe drug action. Antihistamines specifically act as receptor antagonists, not general activators. They inhibit histamine effects without stimulating other pathways, making this choice inaccurate for explaining the mechanism of antihistamines in allergy management.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A reason: To calculate volume, divide the ordered dose (40 mg) by the concentration (20 mg/mL): 40 ÷ 20 = 2 mL. Choice A (5 mL) delivers 100 mg (5 × 20), far exceeding the ordered dose, risking fluid and electrolyte imbalances, making it incorrect for safe administration.
Choice B reason: The correct volume is 40 mg ÷ 20 mg/mL = 2 mL. Choice B (6 mL) delivers 120 mg (6 × 20), significantly overdosing Lasix, which could cause severe dehydration, hypokalemia, or hypotension. This excessive dose is unsafe and incorrect for the prescribed administration.
Choice C reason: Calculating 40 mg ÷ 20 mg/mL yields 2 mL. Choice C (4 mL) delivers 80 mg (4 × 20), doubling the ordered dose. This could lead to excessive diuresis, electrolyte disturbances, or hypotension, making it an incorrect and potentially harmful choice for administration.
Choice D reason: Dividing the ordered dose (40 mg) by the concentration (20 mg/mL) gives 40 ÷ 20 = 2 mL. This volume accurately delivers the prescribed 40 mg of Lasix, ensuring effective diuresis for conditions like edema or heart failure while minimizing risks, making it the correct choice.
Correct Answer is D
Explanation
Choice A reason: NPH insulin is not mixed with insulin glargine, as glargine’s pH and formulation cause precipitation or altered pharmacokinetics when combined. NPH can be mixed with regular insulin, as they are compatible, making this choice incorrect for the patient’s reported practice.
Choice B reason: NPH and regular insulin are compatible and routinely mixed in one syringe to provide both intermediate and short-acting coverage. They don’t react chemically or lose efficacy when combined properly, making this choice incorrect, as mixing is a standard practice in diabetes management.
Choice C reason: Mixing NPH and regular insulin does not increase potency; it combines their pharmacokinetics for basal and prandial glucose control. The mixture delivers the additive effects of each insulin’s profile without enhancing overall potency, making this choice inaccurate for their combined action.
Choice D reason: Mixing NPH (intermediate-acting) and regular insulin (short-acting) is an accepted practice to manage type 1 diabetes with one injection, covering basal and prandial needs. Proper technique (drawing regular insulin first) ensures stability, making this the correct choice for the patient’s reported insulin administration.
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