Lecture 2: Pharmacokinetics

Overview

Pharmacokinetics is the study of how drugs move through the body over time. It involves understanding the processes of absorption, distribution, metabolism, and excretion (ADME) of drugs.

Key Concepts

Absorption

• Definition: The process by which a drug enters the bloodstream.
• Factors Influencing Absorption:
  • Route of administration (oral, intravenous, etc.).
  • Drug formulation and solubility.
  • Presence of food or other substances in the stomach.
  • Blood flow to the absorption site.

Distribution

• Definition: The dispersion or spread of substances throughout the fluids and tissues of the body.
• Influencing Factors:
  • Blood flow to tissues.
  • Tissue permeability.
  • Binding of drugs to plasma proteins.
  • Volume of distribution.

Metabolism

• Definition: The chemical alteration of a drug by the body.
• Sites: Primarily in the liver.
• Phases:
  • Phase I: Modification through oxidation, reduction, or hydrolysis.
  • Phase II: Conjugation with another substance to increase solubility.
• Factors: Enzyme activity, genetic factors, disease states, age, and drug interactions.

Excretion

• Definition: The removal of drugs from the body.
• Primary Route: Renal excretion (urine).
• Other Routes: Biliary excretion (feces), sweat, saliva, and breast milk.

Pharmacokinetic Models

• Compartmental Models: Simplifies the body into compartments where drugs move in and out.
• Non-compartmental Models: Uses statistical methods to predict drug behavior without assuming compartments.

Clinical Applications

• Understanding pharmacokinetics helps in dose adjustment, optimizing therapeutic regimens, and minimizing toxicity.
• Important for drug development and regulatory processes.

Summary

Pharmacokinetics involves complex processes that determine the concentration of drugs in the plasma over time. It is crucial for effective and safe drug therapy, necessitating a strong grasp of the ADME principles.