MECHANISMS OF DRUG ABSORPTION

This document discusses renal and non-renal routes of drug excretion. It describes the key organs and processes involved in excretion, including the nephron in renal excretion and factors that determine if a drug is excreted renally or non-renally. Non-renal excretion includes biliary excretion through the liver and bile ducts. Clearance, excretion ratio, and other pharmacokinetic concepts relating to measurement of excretion are also covered.

The phenomenon of complex formation of drug with protein is called as Protein drug binding. The proteins are particularly responsible for such an interaction. A drug can interact with several tissue components.

The details about the elimination of the drug from the body by various methods. drug metabolism, drug transformation, drug elimination process. factors affecting.

This document discusses linear and nonlinear pharmacokinetics. [1] Linear pharmacokinetics follow first-order kinetics where the rate of drug absorption, distribution, metabolism and excretion is proportional to dose. [2] Nonlinear pharmacokinetics occur when these processes become saturated at high doses due to limited enzyme or transporter capacity. [3] Michaelis-Menten kinetics are often used to model nonlinear processes and estimate parameters like Vmax and Km.

Factors influencing absorption of drugs can be categorized as pharmaceutical or patient related. Pharmaceutical factors include drug properties like solubility, particle size and polymorphism that impact dissolution rate, a key step for absorption. Patient factors involve aspects like age, disease state, gastrointestinal pH and transit time. Together, these factors determine the extent and rate of drug absorption after oral administration.

FACTORS AFFECTING DRUG ABSORPTION Physicochemical factors Pharmaceutical factors Patient related factors

This document discusses various approaches to enhancing the bioavailability of drugs, including enhancing drug solubility, permeability, stability, and gastrointestinal retention. It describes how bioavailability can be improved by increasing a drug's dissolution rate through methods like micronization, nanosuspensions, and use of surfactants. Permeability can be enhanced using lipid technologies, ion pairing, or penetration enhancers. Stability can be improved with enteric coatings or complexation. Gastrointestinal retention time can be lengthened to boost absorption.

The document discusses protein-drug binding, including the two main classes of binding: intracellular and extracellular. It describes the reversible mechanisms of binding such as hydrogen bonds and hydrophobic bonds. Key factors that affect protein-drug binding are the physicochemical properties of the drug and protein, their concentrations, and the number of binding sites. The significance of protein binding is that the bound fraction of a drug is pharmacologically inactive.

The various factors that determine the extend of binding of drugs to various proteins present in the body is outlined in this presentation.

Introduction to biopharmaceutics, mechanism of drug absorption, ADME, Transport mechanism of drug absorption.

Factors that can affect protein-drug binding include drug properties, protein properties, drug interactions, and patient characteristics. Drug properties like lipophilicity, concentration, and affinity determine binding, while protein concentration and binding sites influence binding. Drug interactions can occur via competition for binding sites or with normal constituents. Patient age, genetic variations, and disease states can also impact binding by altering protein levels.

The document discusses nonlinear pharmacokinetics and chronopharmacokinetics. Nonlinear pharmacokinetics occurs when the body's absorption, distribution, metabolism, or excretion of a drug becomes saturated at higher doses. This can cause the rate of drug elimination to decrease. Examples of processes that can become saturated include drug metabolism and renal excretion. Circadian rhythms can also impact drug pharmacokinetics by influencing absorption, distribution, metabolism, and excretion over 24-hour periods. Accounting for these temporal changes can improve drug therapy for circadian phase-dependent diseases.