ABSORPTION OF DRUGS - GENERAL PHARMACOLOGY
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This document discusses drug absorption, which refers to how a drug enters the bloodstream from its site of administration. There are four main methods of drug absorption: passive diffusion, facilitated passive diffusion, active transport, and pinocytosis. Passive diffusion involves drugs moving freely across cell membranes down a concentration gradient. Facilitated passive diffusion uses carrier molecules to transport drugs that have low lipid solubility. Active transport transports drugs against a concentration gradient using carrier proteins and ATP. Pinocytosis involves engulfing fluids or particles by a cell through endocytosis. The rate and extent of drug absorption depends on factors like the drug's lipid solubility, size, and ionization state as well as the route of administration.
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This document discusses drug absorption mechanisms. It begins by defining absorption and noting the importance of both drug concentration and rate of absorption. The main mechanisms of drug absorption are then described in detail: passive diffusion, pore transport, carrier-mediated transport including facilitated diffusion and active transport, ionic or electrochemical diffusion, ion-pair transport, and endocytosis. Various factors affecting each mechanism are also discussed. In conclusion, the mechanisms by which different drug types are typically absorbed are summarized.
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1. The document discusses drug absorption through the gastrointestinal tract. There are three major routes of administration: enteral, parenteral, and topical.
2. Drug absorption involves various mechanisms including passive diffusion, carrier-mediated transport, and active transport. The rate-limiting step is the slowest step that controls the overall rate of drug appearance in systemic circulation.
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When a drug is administered orally, it is absorbed through the gastrointestinal tract and enters the portal circulation, which carries blood directly from the intestines to the liver. This exposes the drug to high concentrations of hepatic drug metabolizing enzymes before it reaches systemic circulation. Many drugs, including propranolol, are extensively metabolized in the liver during first pass. This reduces the amount of unchanged/active drug that reaches the systemic circulation compared to intravenous administration, which bypasses first pass metabolism. Therefore, a higher oral dose is needed to achieve the same systemic drug concentration as a lower intravenous dose.
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The document discusses drug absorption from the gastrointestinal tract. It covers the mechanisms of drug absorption including transcellular, paracellular, and vesicular transport. The key sites of drug absorption in the GI tract are the small intestine, due to its large surface area and permeability. Factors that influence drug absorption include physicochemical properties of the drug like solubility and dissolution rate, pharmaceutical factors like dosage form, and patient factors like disease state and gastrointestinal contents.
Biological process involved in drug targetting
Cellular uptake of drugs can occur through passive diffusion of small molecules or active transport of larger particles via endocytosis, exocytosis, phagocytosis, or pinocytosis. Transport across epithelial barriers relies on passive diffusion, carriers, or endocytosis. Extravasation from blood vessels depends on permeability and physicochemical drug properties, while lymphatic uptake drains drug molecules from tissues. The reticuloendothelial system phagocytoses pathogens and debris from circulation and tissues.
toxicokinetics.ppt
The document discusses toxicokinetics, which is the study of how chemicals move through the body via absorption, distribution, metabolism, and excretion. It specifically addresses:
- Toxicokinetics examines these four processes to understand what the body does to a toxicant.
- Radio labeled doses of chemicals can be used to track their fate throughout tissues and elimination from the body, but may not show the amounts of parent chemicals versus metabolites.
- Absorption of chemicals can occur via passive diffusion, active transport, or facilitated transport across membranes depending on properties like solubility and size. Factors like pH, concentration, food, and gastrointestinal factors influence absorption.
BIOPHAMACEUICS- UNIT 1- DRUG ABSORPTION
Introduction to biopharmaceutics, mechanism of drug absorption, ADME, Transport mechanism of drug absorption.
Biopharmaceutics: Mechanisms of Drug Absorption
Biopharmaceutics is the study of factors influencing drug absorption, distribution, metabolism and excretion (ADME). There are three main mechanisms of drug absorption in the body: 1) transcellular/intracellular transport across epithelial cells, 2) paracellular/intercellular transport between epithelial cells, and 3) vesicular or corpuscular transport through endocytosis. Transcellular transport can occur passively through diffusion, pores or ion pairs, or actively through carriers or pumps. Paracellular transport is between tight cell junctions or through temporary openings. Vesicular transport involves pinocytosis or phagocytosis of substances into cells.
Absorption of drug
Dr. Nilesh S. Kulkarni discusses drug absorption mechanisms. There are three major routes of drug administration: enteral, parenteral, and topical. Gastrointestinal absorption involves three mechanisms: transcellular/intracellular transport, paracellular/intercellular transport, and vesicular transport. Transcellular transport can occur via passive diffusion, active transport, facilitated diffusion, or ion-pair transport. Paracellular transport involves permeation through tight junctions or temporary openings between cells. Vesicular transport involves endocytosis of materials through pinocytosis or phagocytosis.
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ABSORPTION OF DRUGS - GENERAL PHARMACOLOGY
- 1. D R . I . S H E I K N A S A R A S S O C I A T E P R O F E S S O R D E P A R T M E N T O F P H A R M A C O L O G Y ABSORPTION OF DRUG
- 2. ABSORPTION OF DRUG PHARMACOKINETIC -the branch of pharmacology that studies the fate of pharmacological substances in the body, as their absorption, distribution, metabolism, and elimination. DRUG ABSORPTION is a pharmacokinetic parameter that refers to the way a drug is absorbed from a pharmaceutical formulation into the bloodstream.
- 3. ABSORPTION is the process by which drug molecules gain access to the bloodstream from the site of drug administration. The speed of this process (THE RATE OF DRUG ABSORPTION) and its completeness (THE EXTENT OF DRUG ABSORPTION) depend on the route of administration.
- 4. METHODS OF DRUG ABSORPTION I. PASSIVE DIFFUSION II. FACILITATED PASSIVE DIFFUSION III. ACTIVE TRANSPORT IV. PINOCYTOSIS
- 5. I.PASSIVE DIFFUSION Drugs diffuse across a cell membrane from a region of high concentration (eg, GI fluids) to one of low concentration (eg, blood). Diffusion rate is directly proportional to the concentration gradient but also depends on the molecule’s lipid solubility, size, degree of ionization, the area of absorptive surface.
- 6. II.FACILITATED PASSIVE DIFFUSION Certain molecules with low lipid solubility (eg, glucose) penetrate membranes more rapidly than expected. A carrier molecule in the membrane combines reversibly with the substrate molecule outside the cell membrane, and the carrier-substrate complex diffuses rapidly across the membrane, releasing the substrate at the interior surface. In such cases, the membrane transports only substrates with a relatively specific molecular configuration, and the availability of carriers limits the process. The process does not require energy expenditure, and transport against a concentration gradient cannot occur.
- 7. III.ACTIVE TRANSPORT Active transport requires specific carries and ATP. The specific carrier protein carry the drugs that closerly resemble the structure of the naturally occurring metabolites specific for the carrier. It is capable of transporting from low to high concentration compartments.
- 8. IV.PINOCYTOSIS In Pinocytosis, fluid or particles are engulfed by a cell. Pinocytosis probably plays a small role in drug transport, except for protein drugs. Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane, and bringing it into the cell. Exocytosis describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell.
- 10. THANK YOU