Pharmacokinetics MADE EASY FOR BEGINNERS

Summary

In this video, we continue the pharmacology series with a focus on pharmacokinetics, covering absorption, distribution, metabolism, and excretion of drugs. Key concepts like bioavailability, drug movement through the body, and factors influencing pharmacokinetics are discussed. The video also explains different methods of drug absorption and the impact of drug properties on these processes. Additionally, it covers the elimination of drugs and the difference between first-order and zero-order kinetics. Subscribe and turn on notifications for the next video on pharmacodynamics.

Takeaways

• 💊 Pharmacokinetics (PK) studies the movement of drugs through the body, from absorption to excretion.
• 🧬 PK parameters include absorption, distribution, metabolism, and elimination (ADME).
• 🔬 Drug absorption involves the movement of a drug into the bloodstream, affected by the method of administration and drug properties.
• 💉 Intravenous (IV) medications provide 100% bioavailability since they are administered directly into the bloodstream.
• 📊 Distribution refers to the delivery of a drug from the bloodstream to tissues, influenced by blood flow, polarity, and drug size.
• 🧪 Metabolism is the body's process of breaking down drugs, primarily occurring in the liver.
• 🚮 Elimination is the removal of drugs and their metabolites from the body, mainly via the kidneys and biliary system.
• ⚖️ First-order kinetics means the rate of drug elimination is proportional to its concentration in the body.
• 🕒 Zero-order kinetics means the drug is eliminated at a constant rate, regardless of concentration, making half-life calculations meaningless.
• 📈 Volume of distribution (Vd) indicates a drug's propensity to remain in plasma or distribute to tissues, affecting dosing requirements.

Q & A

What is the main focus of this video in the pharmacology series?

The main focus of this video is to provide a good review on pharmacokinetics and discuss the different parameters involved in the movement of drugs through the body.

What does 'PK' in pharmacokinetics stand for and what does it represent?

'PK' in pharmacokinetics stands for 'pharmaco-kinetic', where 'pharmaco' means medication and 'kinetic' refers to movement, representing the movement of drugs through the body.

How does the body process drugs after they enter, excluding intravenous medications?

After drugs enter the body, excluding intravenous medications, they undergo absorption, distribution, metabolism, and excretion. These are the four main pharmacokinetic parameters.

What factors can influence the pharmacokinetic parameters of a drug?

Factors that can influence pharmacokinetic parameters include patient-related factors such as age, weight, and overall health, as well as drug properties like acidity/basicity, lipophilicity, size, and charge.

What are the different methods through which a drug can cross a membrane to enter the bloodstream?

Drugs can cross a membrane through passive diffusion, facilitated diffusion, active diffusion, and endocytosis, depending on the drug's properties and the presence of carrier proteins or energy requirements.

Why is bioavailability an important concept in pharmacokinetics?

Bioavailability is important because it refers to the amount of drug absorbed that reaches the bloodstream, which affects the drug's efficacy and the percentage of the dose that actually contributes to the therapeutic effect.

How does the distribution of a drug depend on its biochemical properties and the individual's characteristics?

The distribution of a drug depends on its lipophilicity, size, and charge, as well as the individual's blood flow, tissue permeability, and the presence of barriers such as the blood-brain barrier.

What is the volume of distribution and how does it relate to dosing?

The volume of distribution is a theoretical volume that indicates the propensity of a drug to remain in the plasma or redistribute into the tissues. It is important for dosing because a high volume of distribution requires higher doses to achieve a given plasma concentration, while a low volume requires lower doses.

What are the primary ways through which drugs and their metabolites are eliminated from the body?

The primary ways for drug elimination are through the kidneys and the biliary system, with the liver releasing drugs into the bile, which then moves into the gastrointestinal tract for excretion.

What are the differences between first-order and zero-order elimination kinetics?

First-order elimination kinetics means the rate of elimination is proportional to the drug's concentration, with a constant half-life. Zero-order elimination kinetics means the rate of elimination is constant and independent of the drug's concentration, with the percentage of drug eliminated changing over time and no constant half-life.