Pharmacology: Pharmacokinetics of Drugs

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary mechanism of endocytosis for drug delivery?

Endocytosis involves the engulfment of a drug molecule by the cell membrane, transporting it into the cell by pinching off the drug-filled vesicle.

How does pH affect the absorption of weak acids and bases?

The pH affects the equilibrium between the charged and uncharged forms of the drug, thus influencing which form can permeate the membrane.

Explain saturation kinetics in relation to drug transport.

Saturation kinetics refers to the process where the rate of drug transport by a carrier reaches a maximum as all binding sites become occupied.

What role does the Henderson-Hasselbalch equation play in drug absorption?

The Henderson-Hasselbalch equation helps determine the ratio of charged to uncharged forms of a drug, which affects its permeability and absorption across membranes. Signup and view all the answers

Why do uncharged drug forms pass through membranes more readily than charged forms?

Uncharged drug forms are more lipid-soluble and can diffuse more easily through lipid membranes compared to charged forms. Signup and view all the answers

What are the four main stages of pharmacokinetics?

The four main stages of pharmacokinetics are absorption, distribution, metabolism, and elimination. Signup and view all the answers

How does passive diffusion function in drug absorption?

Passive diffusion allows drugs to move across cell membranes from an area of high concentration to one of low concentration without using energy. Signup and view all the answers

Describe facilitated diffusion and its energy requirements.

Facilitated diffusion involves specialized carrier proteins that transport drugs from high to low concentration areas without requiring energy. Signup and view all the answers

What role does the liver play in drug metabolism?

The liver metabolizes drugs, transforming them into active or inactive compounds through various enzymatic processes. Signup and view all the answers

What drives the process of active transport in drug absorption?

Active transport is driven by the hydrolysis of adenosine triphosphate (ATP), requiring energy to move drugs against their concentration gradient. Signup and view all the answers

Explain the elimination phase of pharmacokinetics.

The elimination phase involves the removal of drugs and their metabolites from the body, primarily through urine, bile, or feces. Signup and view all the answers

What is the significance of lipid solubility in drug absorption?

Lipid solubility is significant because it enhances a drug's ability to diffuse across biological membranes. Signup and view all the answers

What characterizes the process of drug distribution in the body?

Drug distribution is characterized by the reversible movement of drugs from the bloodstream into interstitial and intracellular fluids. Signup and view all the answers

Study Notes

Pharmacology

Pharmacology is the science of drugs.

Pharmacokinetics of Drugs

Pharmacokinetics describes how the body absorbs, distributes, metabolizes, and excretes drugs.
Absorption: Drug absorption from the administration site into the bloodstream.
Distribution: The drug moves from the bloodstream into interstitial and intracellular fluids.
Metabolism: The drug is chemically altered by the liver, kidneys, or other tissues.
Elimination: The drug and its metabolites are removed from the body in urine, bile, or feces.
This process follows a sequence with drug absorption, distribution, metabolism, and elimination. The diagram shows absorption, distribution, metabolism, and elimination as sequential steps; the diagram also shows these concepts as inputs and outputs.

Absorption of Drugs

Absorption is the movement of drugs from the administration site to the bloodstream.
Mechanisms of drug transport include:
- Passive diffusion: The driving force is the concentration gradient, moving from higher concentration to lower concentration. Lipid-soluble drugs readily cross biological membranes because of their solubility in the lipid bilayer membrane.
- Facilitated diffusion: specialized transmembrane carrier proteins facilitate the passage of large molecules, changing their conformation to move drugs into or out of cells. This does not require energy and can be saturated.
- Active transport: Carrier proteins are driven by energy (often from ATP hydrolysis). Drugs can move against a concentration gradient. This process shows saturation kinetics for the carrier.
- Endocytosis: The cell membrane engulfs and transports drugs into the cell. Drugs with exceptionally large size can use this method.

Effect of pH on drug absorption

Most drugs are weak acids or weak bases.
The charged form of an acid or base goes through a membrane less readily compared to the uncharged form. For weak acids, the uncharged form passes through membranes readily, whereas the charged form doesn't. Conversely, for weak bases, the uncharged permeable from passes more readily through membranes compared to the charged form.
The effective concentration of the permeable form is determined by the ratio between the charged and uncharged forms. This ratio is dependent on pH and pKa (Henderson-Hasselbalch equation.)

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the key concepts of pharmacokinetics in this quiz, covering how drugs are absorbed, distributed, metabolized, and eliminated by the body. Understand the sequential processes that determine the fate of medications within the body, and dive deep into the mechanisms of drug transport. Test your knowledge on the fundamentals of drug action and metabolism.