Farmacocinética: ABSORÇÃO | Aula 3 | Farmacologia rápida e fácil | Flavonoide

Summary

This video lesson introduces the concept of pharmacokinetics, focusing on the absorption phase. It explains how drugs are absorbed into the bloodstream from various administration sites, such as orally or intravenously. The script covers different mechanisms of crossing cell membranes, including passive diffusion, facilitated diffusion, active transport, and endocytosis. It discusses factors influencing drug absorption, such as the drug's lipophilicity, molecular weight, and the pH of the environment. Additionally, it emphasizes the importance of the absorption area, gastrointestinal motility, and pathological conditions. The lesson concludes with an invitation to follow the channel for upcoming lessons on drug administration and biodisponibility.

Takeaways

• 😀 Absorption is the first stage of pharmacokinetics, where the drug passes from the site of administration to the bloodstream.
• 😀 Some drugs, like topical treatments, do not need to be absorbed into the bloodstream since they act locally on the site of administration.
• 😀 The blood circulates from the intestines to the liver, then to the heart and lungs, before reaching different tissues, including the target site of the drug.
• 😀 Absorption involves crossing cellular membranes, and drugs face challenges in crossing these membranes because of their lipid nature.
• 😀 Four main ways drugs cross membranes: passive diffusion, facilitated diffusion, active transport, and endocytosis.
• 😀 Passive diffusion occurs when drugs move from areas of high concentration to low concentration, without requiring energy.
• 😀 Facilitated diffusion uses carrier proteins to help large molecules cross membranes, using concentration gradients.
• 😀 Active transport requires energy (ATP) to move drugs against concentration gradients using specific membrane proteins.
• 😀 Endocytosis involves the cell engulfing large molecules, requiring energy to transport the drug inside the cell.
• 😀 Factors affecting absorption include the drug's lipophilicity, molecular size, ionization, concentration, and the area available for absorption, such as the intestines being more efficient than the stomach.

Q & A

What is absorption in pharmacokinetics?

Absorption in pharmacokinetics refers to the process through which a drug passes from its site of administration into the bloodstream.

Why don't some medications need to be absorbed?

Some medications, like topical drugs (e.g., eye drops), do not need to be absorbed into the bloodstream because they are administered directly at the site of action.

What are the different types of drug administration routes mentioned?

The video mentions oral administration and intravenous administration. Oral administration requires absorption, while intravenous administration bypasses absorption for a faster effect.

What is the role of blood circulation in drug absorption?

Drugs are absorbed into the bloodstream, and the blood circulation carries them to different parts of the body, including the site of action.

How do drugs cross cell membranes during absorption?

Drugs cross cell membranes through four primary mechanisms: passive diffusion, facilitated diffusion, active transport, and endocytosis.

What is passive diffusion, and how does it work?

Passive diffusion is a process where drugs move from an area of higher concentration to an area of lower concentration without requiring energy. It relies on the concentration gradient.

What is facilitated diffusion, and how does it differ from passive diffusion?

Facilitated diffusion is similar to passive diffusion in that it relies on concentration gradients. However, it involves protein carriers that help larger molecules pass through the membrane.

What is the difference between active transport and passive transport?

Active transport requires energy (ATP) to move drugs against a concentration gradient, while passive transport does not require energy and relies on the gradient for movement.

How does the lipophilicity of a drug affect its ability to cross membranes?

Lipophilic drugs are more likely to cross membranes because the cell membrane's lipid bilayer allows lipophilic substances to pass through more easily.

How does the pH of the environment influence the absorption of weak acids and weak bases?

The pH of the environment affects whether weak acids and weak bases will be ionized or non-ionized. Non-ionized forms are more lipophilic and can cross membranes more easily, which leads to better absorption in certain environments.

What role does the surface area of the intestine play in drug absorption?

The larger the surface area of the intestine, the higher the probability that drug molecules will collide with the membrane and be absorbed. This is why absorption is more efficient in the intestine than in the stomach.

What factors affect drug absorption besides the properties of the drug?

Factors such as gastrointestinal motility, gastric emptying time, vascularization, and the presence of food in the stomach all influence how quickly and efficiently a drug is absorbed.