Farmacocinética: METABOLIZAÇÃO | Aula 6 | Farmacologia rápida e fácil | Flavonoide

Summary

This video tutorial on pharmacology explains the essential concepts of metabolism, specifically how substances in the body are chemically transformed through enzymatic reactions. It highlights the importance of the liver, lungs, and intestines in metabolizing drugs, and covers the process of biotransformation from lipophilic to more hydrophilic forms. The video also discusses prodrugs, enzyme families like cytochrome P450, and factors influencing drug metabolism, such as age, liver health, and tolerance. A key concept introduced is half-life, which determines the timing for taking subsequent doses of medication for effective treatment.

Takeaways

• 😀 Metabolism involves transforming substances in the body through chemical reactions, making them more water-soluble and easier to excrete.
• 😀 Both endogenous substances (like neurotransmitters and hormones) and exogenous substances (like drugs and food) undergo metabolism.
• 😀 The liver is the primary organ responsible for metabolism, but other tissues like the lungs and intestines also contribute.
• 😀 Medications taken orally often undergo 'first-pass metabolism,' where the liver processes the drug before it reaches the bloodstream.
• 😀 Prodrugs are designed to be inactive until metabolized by the liver, turning them into active metabolites with therapeutic effects.
• 😀 Some drugs can be metabolized into toxic metabolites, which may pose risks to the body despite the intended therapeutic effects.
• 😀 Metabolism reactions can be divided into two phases: Phase 1 (oxidation, reduction, and hydrolysis) and Phase 2 (conjugation with larger molecules).
• 😀 Phase 1 reactions prepare molecules for Phase 2 by breaking them into smaller parts or adding/removing atoms, while Phase 2 reactions further modify the molecule to ensure it's inactive and water-soluble.
• 😀 The cytochrome P450 enzyme family plays a key role in Phase 1 reactions and is involved in drug metabolism.
• 😀 Factors such as age, liver disease, and tolerance affect metabolism. Elderly people and children metabolize drugs more slowly, requiring lower doses, while liver disease can decrease metabolic capacity.
• 😀 The concept of 'half-life' refers to the time it takes for a drug's concentration in the blood to reduce by half, helping determine the dosing schedule for maintaining effective drug levels.

Q & A

What is the main purpose of metabolism in the human body?

The main purpose of metabolism is to transform substances through chemical reactions, making them more water-soluble and easier to eliminate from the body, mainly through urine and feces.

What is the first step in the metabolism process?

The first step involves reactions that make the substance more polar (water-soluble), which can involve oxidation, reduction, and hydrolysis. These reactions prepare the molecule for further modification.

What is the role of the liver in metabolism?

The liver is the main organ responsible for metabolism, but other tissues, such as the lungs and intestines, also play a role in metabolizing substances to a lesser extent.

What is the 'first-pass effect' in drug metabolism?

The 'first-pass effect' refers to the initial metabolism of a drug when it is absorbed through the digestive system and passes through the liver before entering systemic circulation. This can reduce the amount of active drug available.

What are prodrugs and why are they used?

Prodrugs are drugs that are chemically modified to be inactive initially. When they pass through the liver, enzymes modify them into active metabolites, allowing for effective treatment.

What happens if a drug undergoes metabolism and results in a toxic metabolite?

Sometimes metabolism can transform a drug into a toxic metabolite, which is harmful to the body. While the intention is to make the substance safer, in some cases, it becomes more dangerous after metabolism.

What are the two phases of drug metabolism?

Drug metabolism is divided into two phases: Phase 1, which involves reactions like oxidation, reduction, and hydrolysis; and Phase 2, which involves conjugation reactions, where larger groups are added to the molecule to make it inactive and easier to excrete.

What role do enzymes like cytochrome P450 play in metabolism?

Cytochrome P450 enzymes are crucial in Phase 1 of metabolism. They help break down molecules by adding or removing atoms, such as hydrogen or oxygen, to prepare the drug for Phase 2 reactions.

How does age affect drug metabolism?

Age can influence drug metabolism. Older adults tend to metabolize drugs more slowly, so they may need lower doses. Children, on the other hand, may not have fully developed liver function, so they also require adjusted doses.

What is 'half-life' in pharmacology, and why is it important?

Half-life refers to the time it takes for the concentration of a drug in the plasma to decrease by half. This concept is important because it determines how often a drug needs to be administered to maintain an effective concentration in the body.