What best describes a medication with a narrow therapeutic index?
A medication that has a large safety margin.
A medication that has a small difference between the minimum effective dose and the toxic dose.
A medication that does not require monitoring of blood levels.
A medication that has a wide range of safe and effective doses.
The Correct Answer is B
This question defines a critical pharmacological concept regarding drug safety and dosing. It requires understanding the ratio between therapeutic efficacy and toxicity, which is essential for safely administering medications that have narrow margins for error and require frequent laboratory monitoring to prevent adverse reactions.
Choice A rationale
A large safety margin describes a drug with a wide therapeutic index, where the effective dose is much lower than the dose that causes toxicity. This is the opposite of the safety profile of a narrow therapeutic index drug.
Choice B rationale
A narrow therapeutic index means there is a very small difference between the effective dose and the dose that causes toxicity. This requires careful titration and frequent monitoring of plasma drug levels to ensure patient safety during the administration.
Choice C rationale
Drugs with a narrow therapeutic index absolutely require close monitoring of plasma blood levels. Because the margin between efficacy and toxicity is so small, clinical monitoring is mandatory to prevent accidental poisoning or undertreatment during the course of the therapy.
Choice D rationale
A wide range of safe and effective doses describes a drug with a high therapeutic index, which is considered safer and easier to manage clinically because there is a large margin of safety before toxic effects occur in the patient.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
This question addresses diabetes management during illness. It requires understanding the physiological stress response, which increases counter-regulatory hormones that cause hyperglycemia, and applying the "sick day rules" to adjust insulin and maintain hydration while preventing metabolic complications like ketoacidosis in Type 1 patients.
Choice A rationale
Stopping insulin during illness in a Type 1 diabetic is dangerous and leads to diabetic ketoacidosis. The body's metabolic demand for insulin often increases during stress and illness; therefore, insulin must always be continued to prevent critical, life-threatening metabolic derangement.
Choice B rationale
Oral hypoglycemic agents are ineffective for Type 1 diabetes because these patients do not have sufficient endogenous insulin production. Relying on oral agents during illness would lead to severe, uncontrolled hyperglycemia, which is the primary cause of diabetic ketoacidosis in this population.
Choice C rationale
During illness, Type 1 diabetics must continue insulin, monitor blood glucose frequently, and maintain hydration. If unable to eat solids, replacing carbohydrates with liquid equivalents ensures the insulin has fuel to manage, preventing hypoglycemia while maintaining adequate hydration and glycemic control.
Choice D rationale
While continuing insulin and monitoring glucose are correct, restricting fluids to sugar-free versions when the patient is not eating is insufficient. If the patient cannot consume carbohydrates, they need caloric intake to match their insulin and prevent dangerous hypoglycemia from occurring during illness.
Correct Answer is ["1200"]
Explanation
Step 1 is identify the amount of half-lives needed: 200 mg/L ÷ 2 = 100 mg/L (1st half-life), 100 mg/L ÷ 2 = 50 mg/L (2nd half-life), 50 mg/L ÷ 2 = 25 mg/L (3rd half-life).
Step 2 is calculate total time: 3 half-lives × 2 hours/half-life = 6 hours.
Step 3 is 0600 + 6 hours = 1200. Final calculated answer is 1200.
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