Which of the following statements correctly differentiates first-generation and second-generation antihistamines?
Second-generation antihistamines have shorter half-lives and require more frequent dosing compared to first-generation antihistamines.
First-generation antihistamines block both histamine and muscarinic receptors, while second-generation antihistamines primarily block histamine receptors.
First-generation antihistamines are less likely to cause sedation compared to second-generation antihistamines.
Second-generation antihistamines cross the blood-brain barrier, causing significant central nervous system effects.
The Correct Answer is B
A. Second-generation antihistamines have shorter half-lives and require more frequent dosing compared to first-generation antihistamines: Second-generation antihistamines typically have longer half-lives, allowing once-daily dosing. They are designed for sustained action with improved compliance and fewer side effects.
B. First-generation antihistamines block both histamine and muscarinic receptors, while second-generation antihistamines primarily block histamine receptors: First-generation agents, such as diphenhydramine, cross the blood-brain barrier and exert anticholinergic effects by blocking muscarinic receptors. Second-generation antihistamines are more selective for peripheral H1 receptors, resulting in fewer CNS and anticholinergic side effects.
C. First-generation antihistamines are less likely to cause sedation compared to second-generation antihistamines: First-generation antihistamines are more likely to cause sedation because they easily penetrate the blood-brain barrier and affect central H1 receptors, unlike second-generation agents.
D. Second-generation antihistamines cross the blood-brain barrier, causing significant central nervous system effects: These medications are designed not to cross the blood-brain barrier significantly, which is why they are much less sedating and have minimal CNS effects compared to first-generation antihistamines.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is ["4"]
Explanation
Desired dose rate = 15 mcg/min
- Convert the desired dose rate to mg/hr:
1000 mcg = 1 mg and 60 minutes = 1 hour.
Desired dose rate (mg/hr) = 15 mcg/min × (1 mg / 1000 mcg) × (60 min / 1 hr)
= (15 × 60) / 1000 mg/hr
= 900 / 1000 mg/hr
= 0.9 mg/hr
Available concentration = 25 mg / 100 mL
- Calculate the flow rate in mL/hr:
Flow rate (mL/hr) = Desired dose rate (mg/hr) / Concentration (mg/mL)
= 0.9 mg/hr / (25 mg / 100 mL)
= 0.9 mg/hr / 0.25 mg/mL
= 0.9 / 0.25 mL/hr
= 3.6 mL/hr
Round to the nearest whole number:
= 4 mL/hr
Correct Answer is A
Explanation
A. The safe and toxic plasma levels of the drug are very close to each other: A narrow therapeutic index means there is a small margin between the minimum effective concentration and the toxic concentration. Small dosing errors or individual variations in metabolism can lead to toxicity or subtherapeutic effects, requiring close monitoring.
B. The drug has a wide range between its effective dose and toxic dose: This describes a drug with a wide therapeutic index, which allows more flexibility in dosing without significant risk of toxicity. Narrow therapeutic index drugs are the opposite and require precise dosing.
C. The drug requires infrequent monitoring of serum levels: Medications with a narrow therapeutic index often require frequent serum level monitoring to ensure that the drug stays within the safe and effective range. This helps reduce the risk of adverse effects or treatment failure.
D. The drug has a high margin of safety in clinical use: A high margin of safety is characteristic of drugs with a wide therapeutic index. Narrow therapeutic index drugs have a low safety margin and pose higher risks if not carefully dosed and monitored.
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