Introdução à FARMACOCINÉTICA | Aula 2 | Farmacologia rápida e fácil | Flavonoide

Introduction to Pharmacokinetics

Overview of Pharmacokinetics

• Flávia Masson introduces herself as a pharmacist and discusses the focus of the second video lesson on pharmacology, specifically pharmacokinetics and pharmacodynamics.

• The term "pharmacokinetics" is explained: "fármaco" refers to drugs, while "cinética" relates to movement, indicating how drugs move through different compartments in the body.

The Drug's Journey

• The drug is likened to a protagonist in a game whose goal is to establish itself within the body, facing challenges from the body's defenses.

• Each phase of pharmacokinetics represents a challenge that the drug must overcome; although these phases occur simultaneously in practice, they are explained separately for clarity.

Phases of Pharmacokinetics

Key Phases Explained

• The four main phases of pharmacokinetics are identified: absorption, distribution, metabolism, and excretion.

• Absorption: How the drug enters the bloodstream.

• Distribution: How it spreads throughout the body.

• Metabolism: How the body chemically modifies the drug.

• Excretion: How the body eliminates the drug.

Absorption Phase

Mechanism of Absorption

• The primary objective during absorption is for drugs to reach systemic circulation via blood vessels acting as transport routes.

• Various administration routes (vias de administração) allow drugs entry into circulation; however, some drugs can bypass certain phases by being applied topically.

Topical Administration Benefits

• Topical medications can directly target affected areas (e.g., burns), minimizing systemic exposure and potential side effects compared to oral medications that undergo all phases before reaching their site of action.

Distribution Phase

Understanding Distribution

• Once in circulation, drugs travel through various compartments within the body (blood plasma, fat tissue, etc.), akin to navigating different empires.

• The body's attempt at equilibrium among compartments leads to local binding by proteins which may limit free drug availability until saturation occurs.

Compartment Dynamics

• As free molecules escape one compartment due to saturation limits, they encounter similar binding dynamics in subsequent compartments until an overall balance is achieved across all areas.

Metabolism Phase

Metabolic Processes

• Depending on administration route, drugs may face significant metabolic challenges where they undergo irreversible transformations aimed at facilitating elimination from the body.

• A key transformation involves converting lipophilic molecules into more polar forms that are easier for excretion processes.

Biotransformation and Drug Excretion

Understanding Biotransformation

• Biotransformation refers to the process by which our body converts drugs into forms that are easier to eliminate, reducing their duration in circulation and potential side effects.

• The discussion will delve deeper into metabolism in a later class, emphasizing its importance in understanding drug processing.

Phases of Drug Excretion

• The final phase of drug processing is crucial for students to grasp; it involves various pathways through which drugs can be excreted from the body.

• Most medications are primarily excreted via the urinary route (urine), but there are alternative pathways as well, indicating a complex elimination process.

Implications for Medication Dosing

• As drug molecules are expelled from the body, their concentration decreases, signaling when it's appropriate to take the next dose.