Pathological and physiological factors affecting drug absorption, distribution, elimination, and response in man. Gastrointestinal tract physiology and drug absorption. A mechanistic approach to understanding the factors affecting drug absorption. Overview of response to drugs msd manual consumer version. Drug absorption depends on the lipid solubility of the drug, its formulation and the route of administration. After reading this article you will learn about the pharmaceutic factors affecting drug bioavailability. Factors affecting drug absorption and distribution.
Factors affecting drug absorption and distribution request pdf. Formulation factors affecting the dissolution rates of drugs from tablets and capsules, and thus influencing their absorption characteristics, include the surface area, polymorphic form, solvates and salt of the drug, the excipients and the process of manufacture. Now this lecture from absorption of drug with factor affecting drug absorption. In order to develop a drug product that elicits the desired therapeutic objective, the pharmaceutical scientist must have a thorough understanding of the biopharmaceutic properties of the drug and drug product and the physiologic and pathologic factors affecting drug absorption from the application site. Impact of physiological, and biopharmaceutical factors in absorption and metabolism mechanisms on the drug oral bioavailability of rats and humans. For the processes of drug absorption, distribution, and elimination.
Each route of administration has its own anatomical, physiological, and pathological factors that can affect drug bioavailability. Some disorders like diabetic neuropathy causes gastric. In pharmacology, bioavailability is a subcategory of absorption and is the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. Factors affecting bioavailability global events usa. Pharmacokinetics of drugs following iv bolus, iv infusion, and oral. The absorption of ionized forms of a drug would cause the phabsorption curve to shift to the right for a weak acid, and to the left for a weak base, the extent of the shift depends on the relative permeability of the ionized form of the drug. The speed with which drugs move in and out of the body varies widely among different people.
Drug absorption, drug distribution, drug dissolution, drug solubility introduction. In addition, it is common for multiple medical conditions to be present in older patients which can lead to a greater potential for medication problems due to polypharmacy. Pharmacokinetics in the older patient in general drug absorption, distribution in the body, activity, metabolism and excretion can all change as a result of ageing. The plasma and the ecf volume also increase but there is a fall in albumin content. The following table highlights some of these other factors. Although drugs are used primarily for the treatment of disease, surprisingly little is known of the way in which disease states or physiological factors modify drug action in man. Pdf overview of factors affecting oral drug absorption. Other factors affecting drug absorption and distribution. For drugs which can be ionized the drugs pka and the ph of the blood will have a large effect on the transfer rate across the capillary membrane. Factors to be considered when choosing certain route. With both drugs, absorption from the intestines proceeded 10 times faster at a given ph than from the stomach. Pharmaceutic factors affecting drug bioavailability toxicology.
The rectum is an interesting area for drug absorption because it is not buffered and has a. Pharmacokinetic factors influencing variability in human drug response. In the first chapter, the principles underlying drug absorption, distribution, metabolism and elimination are described, with drug metabolism highlighted within the context of these fundamental processes. Absorption barrier an overview sciencedirect topics. Absolute dose of a drug varies with species as different species are of different sizes. This article throws light upon the eight main physiological factors that affect the rate of drug absorption. Routes of administration factors to be considered when. Physiological factors that impact oral drug absorption. Drug metabolism and pharmacokinetics in malnutrition. Overview of factors affecting oral drug absorption naining song a,b, shaoy u zhang b, changxiao liu a a tianjin state key laboratory of pharmacokinetics and pharmaco dynamics, tianjin inst. Terms in this set 27 what are the 6 major factors affecting drug absorption related to the composition of the drug. Pharmaceutical factors a chemical factors b physicochemical properties of drug substances 1.
Low molecular weight drugs pass through by simple diffusion. Drug absorption involves the movement of the drug from its injectionadministration site into the systemic circulation. Intravenous administration does not involve absorption and, hence, there is no loss of drug. List two physiologic factors that can alter each of the processes of absorption. A mechanistic approach to understanding the factors affecting. Factors affecting drug absorption small intestine stomach. The rate and extent of absorption after a particular route of administration are dependent on many drug and patient factors. Drug absorption occurs from the gut wall by passive diffusion. The epithelial absorption profile of drugs may vary regarding the rate and the lag time. Laxatives and diarrhea, which speed up the passage. Key factors influencing adme properties of therapeutic. Director clinical pharmacology program september 30, 2010 office of clinical research training and medical education national institutes of health clinical center goals of drug absorption and bioavailability lecture factors affecting drug absorption estimation of. Already at this stage, there are several individual factors that can affect drug response, such as the patients age, gastric ph, a highfat diet, cardiovascular or digestive diseases, rate of gastric emptying and gastric motility. Othe af90t is a fully automatic capsulefilling machine that can fill a large variety of powder formulations into hard gelatin capsules.
Physiological factors and drug absorption pharmacokinetics. Goals of drug absorption and bioavailability lecture factors affecting drug absorption estimation of bioavailability clinical significance of differences in bioavailability prediction of bioavailability in highthroughput drug candidate screening. Physiologically, a drugs absorption is enhanced if there is a large surface area available for absorption e. This chapter discusses in detail the factors affecting protein and peptide absorption, barriers to protein absorption, penetration. There are many recent advances and factors affecting bioavailability. Physiological factors influencing oral drug absorption. The ph of the intestinal lumen, gastric emptying time, intestinal transit time, sur face area of the gastrointestinal tract, intes tinal blood flow, gut bacteria and gut wall. This process is more complex if the person takes other drugs and has other diseases, because drug drug and drug disease interactions are possible. In rectal absorption both low and high molecule weight compounds in a constant ratio of absorption. The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug concentration gradient. This article throws light upon the five major factors modifying drug effect and dosage. Explain the consequences of increased or decreased drug absorption. There are various factors which control of absorption through the oral route and thus affect the.
In addition to protein availability, other factors may affect drug absorption and distribution in the body as a whole or at specific sites within the body. These dressings combine physically different components into a single product and. Physiological factors affecting absorption pharmatutor. Factors affecting distribution of drug tissue permeability of drug 1. Factors affecting drug absorption flashcards quizlet. The gi tract is the most favored site of absorption because of many reasons like high surface area available for absorption, availability of various transport mechanisms, high. Pharmaceutical factors a chemical factors b physicochemical properties of drug substances.
Knowledge of the adme process and the factors influencing drug absorption and. Large interindividual variations in drug response can arise from multiple genetic and environmental factors affecting drug absorption, distribution, biotransformation, excretion, interaction with receptor sites, or combinations of these. Drug absorption and factor affecting drug absorption by dr. It is well recognised that the clinical response to drug administration varies widely between individuals and that most of this variability is pharmacokinetic in origin. Laxatives and diarrhea, which speed up the passage of substances through the digestive tract, may reduce drug absorption. In pharmacokinetics, bioavailability is related to absorption and is the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. Request pdf factors affecting drug absorption and distribution the pharmacokinetic properties of a drug comprise the relationship between its absorption. It also occurs by subcutaneous, intra muscular and transdermal routes of administration of drugs. Food, other drugs, and digestive disorders can affect drug absorption and bioavailability.
Explain the meaning of the terms absorption, distribution, metabolism, and excretion. Factors affecting surface drug absorption many factors affect how the application of a particular drug will be absorbed by the skin surface. A slightly dated article by orme 1984 could also act as a standalone resource for preexam reading, and was used top. Some drugs are not affected by food, while the absorption of a third group of drugs is enhanced by food bile secretion by liver in response to food in gi tract increases drug absorption.
Factors affecting drug absorption authorstream presentation. Absorption is the process by which drug molecules cross biological membranes. List the factors that influence drug absorption and explain how they alter drug uptake. Factors which influence gastrointestinal drug absorption. Oral absorption, intestinal metabolism and human oral. A relatively large volume of nonirritant drugs can be given.
Apr 27, 2016 introduction of absorption transport process factors affecting drug absorption with examples. Factors affecting dissolution rate divided into five classes a. Pathological and physiological factors affecting drug. Levothyroxine lt4 is a drug with a narrow therapeutic index, applied in small amounts micrograms, which makes interactions in the absorption phase clinically significant. Factors affecting this absorption will depend on the physiology of the administration sites and the membrane barriers present at those sites that the drug needs to cross in order to reach the systemic circulation. A mechanistic approach to understanding the factors. It is a process by which absorption of drug from site of administration. Kinetics is the study of the rate of a process and the factors affecting on it. This chapter discusses various aspects of drug absorption and bioavailability. With oral administration, several factors affect the absorption of a drug.
A drug needs to be lipid soluble to penetrate membranes unless there is an active transport system or it is so small that it can pass through the aqueous channels in the membrane. Rate constants for the transport of unionized and ionized drug moieties were determined from the stomach and from the intestine. Pharmacokinetic factors influencing variability in human drug. Factors affecting pharmacokinetics of drugs medicilon inc. Lipid water solubility coefficient is the ratio of dissolution of drug in lipid as compared to water. In order to discuss this topic, the factors affecting drug metabolism will be split into internal i. Learn vocabulary, terms, and more with flashcards, games, and other study tools. In order to gain an insight into the numerous factors that can potentially influence the rate and extent of drug absorption into the systemic circulation, a schematic. This route provides a high local concentration of the drug without affecting the general circulation. Factors affecting drug absorption free download as powerpoint presentation.
Other factors that also impact drug absorption include the following. The placental membrane is a lipid barrier that is less selective than the bloodbrain barrier, allowing the passage of lipidsoluble drugs more easily than watersoluble drugs. The factors affecting absorption of drugs are related both to the drugs and to the body. Because so many factors affect drug response, doctors must choose a drug appropriate for each person and must adjust the dose carefully. Pharmaceutic factors affecting drug bioavailability. The absorption, distribution, and excretion of drugs objectives after studying this chapter, the reader should be able to. Fortunately, martinez and amidon 2002 do an excellent overview of the factors which affect intestinal drug absorption, and this article still seems to be available for free.
We also give an overview of the current tools, technologies, and. Absorption is the process of a drug moving from its site of delivery into the bloodstream. Drug bioavailability an overview sciencedirect topics. Pharmacokinetics in older patients rosemont pharma. The chemical composition of a drug, as well as the environment into which a drug is placed, work together to determine the rate and extent of drug absorption. Drug absorption absorption for the drug to act on the system, its adequate concentration conc. Other routes will require an absorption step before the drug reaches the systemic circulation. Before drugs can be clinically effective, they must be absorbed. Many factors can affect a drug s absorption, distribution, metabolism, excretion, and ultimate effect. Greater the lipid water solubility coefficient, more is the lipid solubility of the drug and greater is the absorption.
The absorption rates varied with ph for both drugs. Re absorption by the urine ph effect, the application of acidic or alkaline drugs, changes the ph of the urine, can reduce renal tubular reabsorption of drugs. Several factors can affect the absorption of a drug into the body. Factors modifying drug effect and dosage pharmacodynamics. Other factors include a persons age, sex, level of physical activity, and level of stress. The bioavailability of active drug can be varied from rapid and complete absorption to a slow, sustained rate of absorption or. Drug absorption drugs merck manuals consumer version. Each route of drug application presents special biopharmaceutic consideration in designing a drug product. Medicilons pharmacokinetics department offers the clients a broad spectrum of high quality of services in the areas of in vitro adme.
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