Mekanisme Absorpsi Obat & Faktor Faktor yang Mempengaruhi Abosrpsi-Materi Kuliah Farmakologi Farmasi

Summary

This video explains the mechanisms of drug absorption across membranes, focusing on various processes like passive diffusion, active transport, receptor-mediated endocytosis, vascular uptake, and phagocytosis. The video highlights factors affecting drug absorption, such as molecular size, solubility, and ionization, along with the role of concentration gradients. It further explores how drugs move from areas of low to high concentration, aided by proteins or other cell structures. The video provides examples of different drug types, including weak acids and bases, and discusses how their properties influence absorption. Overall, it provides a detailed overview of drug transport mechanisms.

Takeaways

• 😀 Passive diffusion is the most common and simplest drug absorption mechanism, driven by the concentration gradient between the administration site and the bloodstream.
• 😀 The speed of absorption via passive diffusion depends on the difference in drug concentration: the greater the difference, the faster the absorption.
• 😀 Drug absorption through passive diffusion requires certain properties, such as a drug size that is not too large and fat solubility for easier membrane crossing.
• 😀 Drugs that are neither too polar nor too nonpolar tend to be absorbed more easily in the body due to their ability to pass through the lipid membrane.
• 😀 The degree of ionization affects drug absorption: weak acids tend to be more ionized in the intestine and more absorbed in the stomach, while weak bases are more absorbed in the intestine.
• 😀 Aspirin, a weak acid, is more absorbed in the stomach due to its stability in the acidic environment, demonstrating the impact of ionization on drug absorption.
• 😀 Active transport, unlike passive diffusion, requires energy and proteins (carrier proteins) to move drugs from areas of low concentration to high concentration across the membrane.
• 😀 The rate of absorption through active transport reaches a constant speed once all available carrier proteins are saturated with the drug.
• 😀 Receptor-mediated endocytosis is another mechanism for drug transport, where drugs are absorbed by the cell through the binding of receptors, leading to membrane folding and drug internalization.
• 😀 Phagocytosis is a process where macrophages help in the transport of drugs across the membrane, encapsulating them within the cell and releasing them into the bloodstream.
• 😀 There are at least five major drug transport mechanisms: passive diffusion, active transport, receptor-mediated endocytosis, vascular endocytosis, and phagocytosis.

Q & A

What is the most common mechanism of drug absorption?

The most common mechanism of drug absorption is passive diffusion. This process occurs when a drug moves from an area of high concentration to low concentration across a membrane, driven by the concentration gradient.

How does the concentration gradient affect drug absorption?

The greater the difference in the concentration gradient between the site of administration and the bloodstream, the faster the drug will be absorbed. As the concentrations equalize, the rate of absorption slows down.

What factors determine whether a drug can pass through passive diffusion?

Several factors affect passive diffusion, including the molecular size of the drug, its solubility in fat, and its degree of ionization. The drug must have an appropriate balance between polarity and nonpolarity, allowing it to cross the membrane effectively.

Why is fat solubility important for drug absorption through passive diffusion?

Fat solubility is crucial because the middle part of the cell membrane is made of lipids (fats). Drugs that are soluble in fat can more easily pass through this lipid-rich layer, facilitating absorption.

How does ionization affect drug absorption?

Drugs that are weak acids or weak bases can become ionized depending on the pH of the environment they are in. Weak acids tend to be non-ionized in acidic environments (like the stomach), aiding absorption, while weak bases tend to be more ionized in acidic conditions, limiting absorption.

What is the role of carrier proteins in active transport?

Carrier proteins help drugs cross membranes by binding to them and transporting them from areas of low concentration to areas of high concentration, requiring energy in the process. This makes active transport an energy-dependent mechanism.

How does the saturation of carrier proteins affect drug absorption?

Once all available carrier proteins are saturated with the drug, the rate of absorption becomes constant, as the number of proteins available to transport the drug is limited. Before saturation, the absorption rate increases with higher drug concentrations.

What are the main steps involved in receptor-mediated endocytosis for drug absorption?

In receptor-mediated endocytosis, a receptor on the cell membrane binds to the drug. The drug-receptor complex then triggers the cell membrane to fold around the drug, forming a vesicle that brings the drug into the cell and releases it into the bloodstream.

What is the difference between vascular absorption and phagocytosis in drug transport?

Vascular absorption involves the formation of a vesicle by the cell membrane that engulfs the drug, while phagocytosis requires the help of macrophages to engulf and transport the drug. Both mechanisms protect drugs from harsh polar or nonpolar environments during transport.

Why might a drug not be absorbed through passive diffusion?

Drugs that are too large, highly polar, or highly nonpolar may not be able to pass through the membrane via passive diffusion. In such cases, other mechanisms like active transport, receptor-mediated endocytosis, or phagocytosis are required for absorption.