Lecture Notes: Therapeutic Index, Half-life, and Mode of Action of Medications

Overview

• Presenter: Cathy from Level Up RN
• Topics Covered: Therapeutic index, half-life, mode of action of medications
• Quiz: Simple quiz at the end to reinforce key concepts

Therapeutic Index (TI)

• Definition: TI compares the minimum effective concentration (MEC) of a drug to its toxic level.
  • Minimum Effective Concentration (MEC): The amount of the drug needed to be effective.
• *High TI:
  • Indicates a large range between MEC and toxic level.
  • Easier to achieve a therapeutic effect without toxicity.
  • Example: Amoxicillin
  • No need for close monitoring of patient’s blood levels.
• *Low TI:
  • Indicates a small range between MEC and toxic level.
  • Higher risk of toxicity due to narrow therapeutic range.
  • Example: Vancomycin
  • Requires close monitoring of patient’s blood levels.

Half-life

• Definition: The time it takes for 50% of a medication to be reduced in the body.
• Short Half-life: Medication leaves the body quickly.
• Long Half-life: Medication leaves the body slowly.
  • Increased risk for toxicity.

Mode of Action of Medications

• Agonists: Activate a receptor in the body.
  • Example: Dilaudid is an opioid agonist that activates opioid receptors to produce analgesia.
• Antagonists: Block receptors in the body.
  • Example: Naloxone is an opioid antagonist that blocks opioid receptors to reverse the analgesic effect of opioids.
• Agonist-Antagonists (Partial Agonists): Act as an agonist or partial agonist at some receptors and as an antagonist at other receptors.

Quiz Questions

1. Question: What type of medication is safer, a medication with a high therapeutic index or a medication with a low therapeutic index?
   • Answer: High therapeutic index.
2. Question: Drugs with a longer half-life have a greater risk for toxicity. True or false?
   • Answer: True.
3. Question: What type of medication blocks a receptor in the body?
   • Answer: Antagonist.

Conclusion

• Encouragement to subscribe, like, and share the channel.
• Invitation to leave comments on what was particularly helpful.