Pharmacology Pharmacokinetics #5

Question

Which is a true statement about a drug’s half-life?

Answers

  1. A half-life of 2 hours means that at 1 hour, the drug is at 50% strength.
    • Rationale:

      This is not the correct answer because a drug’s half-life is the time required for the specific drug to decline it’s dosage in the body to 50%. It does not mean the drug decreases by 50% in half the drug’s half-life.

  2. A drug with a long half-life poses little risk of adverse reaction in the body..
    • Rationale:

      This is not the correct answer because a long-half means a medication takes a longer time to decrease by 50%. This can make adverse reactions more common because the body takes longer to decrease the dosage within the body, hence potentially lengthening the time of adverse reaction.

  3. A half-life of 3 minutes is more common than a drug with a 3 hour half-life.
    • Rationale:

      This is not the correct answer because drugs with short half-lives act then leave the body quickly and they are less common. Cocaine and heroin have short half-lives and are very addictive. Examples of therapeutic emergency medications with a short half-life include sublingual nitroglycerin, which has a half-life of 2-3 minutes.

  4. A drug’s half-life determines how much time separates each dose.
    • Rationale:

      This is the correct answer because a drug’s half-life is the time required for the specific drug to decline it’s dosage in the body to 50%. This is used to determine the safe dosing interval or how much time separates each dose.

Overview

A drug’s half-life is an important consideration during drug therapy since it is used to determine a medication’s dosing interval.

Explanation

Learning Outcomes

A drug’s half-life is the time required for the specific drug to decline it’s dosage in the body to 50%. For example, since morphine’s half-life is 3 hours, the body stores of morphine will decrease by 50% every 3 hours. In other words, 10 mg of morphine in the body will decrease to 5 mg of morphine in 3 hours. Therefore, the medication’s half-life determines the dosing interval or how much time separates each dose.

Test Taking Tip

Be sure to focus on concepts which affect life or death, such as things that affect airway, breathing, or circulation. Side effects of drugs which affect this should be focused on when studying pharmacology.

Video Rationale