Introduction to Pharmacokinetics

Summary

This video explains the process of drug absorption and distribution in the body. It highlights how drugs taken orally are dissolved in the stomach and primarily absorbed in the small intestine. Once absorbed, drugs enter the bloodstream and are transported to various organs, especially the liver, which plays a crucial role in metabolizing the drug into more water-soluble forms. The drug is eventually eliminated from the body through urine, feces, sweat, or respiration. The script emphasizes how chemical properties of drugs influence their absorption, distribution, and elimination processes.

Takeaways

• 😀 Drugs are primarily taken orally and dissolved in the stomach for absorption.
• 😀 The majority of drug absorption occurs in the small intestine due to its large surface area.
• 😀 Drugs must be able to cross epithelial cells in the intestine to be absorbed.
• 😀 Absorption can occur through passive diffusion, paracellular transport, endocytosis, or drug transporter proteins.
• 😀 After absorption, drugs enter the bloodstream and are distributed throughout the body.
• 😀 The liver is the first organ to receive the drug after it enters circulation due to its connection to digestive tract blood vessels.
• 😀 Drugs are delivered to organs with high blood flow, such as the heart and brain, before reaching other body compartments.
• 😀 Drug distribution depends on the drug's chemical properties, including charge and fat solubility.
• 😀 Drug elimination can occur in its original form or as metabolites that are more water-soluble and often inactive.
• 😀 The liver plays a key role in drug biotransformation through its enzymes.
• 😀 Drugs or their metabolites are eventually excreted from the body, primarily through the kidneys in urine, though small amounts can also be excreted in feces, sweat, and respiration.

Q & A

What is the primary route of drug administration discussed in the transcript?

The majority of drugs are taken orally.

Where does the absorption of most drugs primarily occur after ingestion?

The absorption mostly occurs in the small intestine due to its large surface area.

What must a drug be able to do to be absorbed in the intestine?

A drug must be able to cross the epithelial cells that line the intestinal tissue.

What are the possible mechanisms through which a drug can be absorbed across the intestine?

A drug can be absorbed through passive diffusion, paracellular transport, endocytosis, or by the action of drug transporter proteins.

After absorption, where does the drug first travel?

After absorption, the drug moves through the intestinal fluid and then diffuses into the blood circulation.

Why is the liver the first organ to receive a drug after it enters the circulation?

The liver is anatomically linked to the blood vessels leaving the digestive tract, so it is the first organ to receive the drug.

Which organs receive the drug after the liver?

The drug is delivered to organs with high blood flow, such as the heart and brain.

What determines the distribution of a drug in various body compartments?

The distribution depends on the chemical properties of the drug, such as charge and fat solubility.

How is drug elimination or clearance achieved?

Drug elimination occurs either in its original form or after metabolism into more water-soluble and often inactive metabolites.

What is the main site for drug biotransformation, and why is it significant?

The main site for drug biotransformation is the liver, which has large amounts of enzymes that perform this function.

How are drugs typically removed from the body after biotransformation?

Drugs and their metabolites are usually removed by filtration in the kidney and excreted in the urine. Some drugs may also leave the body in small amounts through feces, sweat, or respiration.