CritIC: Pharmacokinetics Series

Introduction

• Hosted by Jessica.
• Focus on pharmacokinetics: absorption, distribution, metabolism, and excretion.
• Target audience: young physicians.
• Aim: Understanding importance and application in clinical practice.

Pharmacokinetics Overview

• Pharmacokinetics: What the body does to the drug.
• Key steps:
  • Absorption: How a drug enters the bloodstream.
  • Distribution: How a drug spreads throughout the body.
  • Metabolism: How a drug is chemically altered by the body.
  • Excretion: How a drug is eliminated from the body.

Case Study: Metoprolol

• Drug classification: Selective beta-1-receptor blocker.
• Clinical effects:
  • Decrease heart rate, contractility, and blood pressure.
  • Makes the heart more energy efficient.

Pharmacokinetics of Metoprolol

• Bioavailability:
  • Oral administration doesn't directly reach beta-1-receptors.
  • Bioavailability is 50-70% due to first-pass effect.
• Volume of Distribution:
  • 5.5L/kg indicates large distribution.
  • Low protein binding (12%).
  • Likely lipid-soluble.
• Metabolism:
  • Primary substrate of CYP2D6.
  • Watch for 2D6 inhibitors (e.g., Prozac) and inducers.
  • Genetic variability in 2D6.
  • Patient’s dosage (100mg/day) effective, thus likely no issue.
• Excretion:
  • Primarily via kidney.
  • 5% unchanged, rest are metabolites.
  • Renal injury not a concern.

Potential Issues

• Interaction with medications affecting CYP2D6.
• Liver failure considerations.

Conclusion and Further Learning

• Gaining proficiency in evaluating pharmacokinetics for patient medications.
• Encouragement to watch further videos on series topics.
• Call to action to share, like, and comment on the series.