Introduction to pharmacokinetics and pharmacodynamics ashp. Drug absorption, drug distribution, drug dissolution, drug solubility introduction. Factors affecting drug absorption and distribution request pdf. The final step involves solubilization or dissolution of the drug substance into the dissolution medium. A drug injected intravascularly directly enters the systemic circulation and exerts its. Other factors that also impact drug absorption include the following. Department of pharmacology adapted from lectures of jeffrey l. Pharmaceutic factors affecting drug bioavailability toxicology. Peristaltic contraction promotes drug absorption by increasing the drug membrane contact and by enhancing dissolution especially of poorly soluble drugs. Intestinal transporters play an important role in drug absorption. 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.
For drug absorption to be most efficient, the properties of the drug itself and the ph of the environment where the drug is located must be considered. Absorption is the process by which drug molecules cross biological membranes. Factors affecting drug abuse in adolescent females in rural. Ppt drug absorption powerpoint presentation free to. The influence of the dosage form on the bioavailability of. Overthecounter meds, dietary supplements, and certain foods also can cause an interaction. But it depends on the amount of carriers by which the drug molecules can be bound. Although the solid solution is an attractive approach to increase drug absorption, only one drug, griseofulvin, is currently marketed in this form. Suspensions a drug in a suspension is in solid form, but is finely divided and has a large surface area. There are many recent advances and factors affecting bioavailability. Pharmacopoeia recommends 6 or 12 units in disintegration or dissolution testing a compounder wheather a b. Factors affecting gastrointestinal absorption of drugs springerlink. Factors affecting drug abuse in adolescent females in. Studies of 45 compound of different chemical classes and a wide range of solubilities revealed that initial dissolution rate of these substances is directly proportional to their respective solubilities.
The speed with which drugs move in and out of the body varies widely among different people. Anatomical and physiological factors affecting drug absorption by r. Factors affecting drug metabolism pdf 1430z03rjj4j idocpub. This process is more complex if the person takes other drugs and has other diseases, because drug drug and drug disease interactions are possible. Long intestinal transit time is desirable for complete absorption of drug e. Just as the absorption and distribution of a drug are influenced by its physicochemical properties so is its interaction with the drug metabolising enzymes. Request pdf factors affecting drug absorption and distribution the pharmacokinetic properties of a drug comprise the relationship between its absorption. 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. 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. 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. Certain changes within each of the four categories will produce uniform or predictable changes in drug absorption. In this case also the carrier proteins are required, but transfer is occurred due to absorption of other molecule, which facilitate movement of drug molecule. The most important factors affecting adsorption are. A drug injected intravascularly directly enters the systemic circulation and exerts its pharmacological effects.
Drug absorption drugs merck manuals consumer version. Physicochemical factors affecting drug absorption i. After reading this article you will learn about the pharmaceutic factors affecting drug bioavailability. Rate of gastric emptying is a major determinant of initial delay in drug absorption. 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. Pharmaceutic factors affecting drug bioavailability. Various processes underlie the successful absorption of drugs. Factors affecting distribution of drug tissue permeability of drug 1. Factors affecting drug absorption small intestine stomach. Physiologic factors related to drug absorption applied. A guide to helping older adults avoid harmful drug effects. For example, highfiber foods and calcium supplements may bind with a drug and prevent it from being absorbed. It is usually associated with oral drugs and their absorption through the git. O factors affecting drug metabolism pharmaceutical chemistry.
Dosage forms eg, tablets, capsules, solutions, consisting of the drug plus other ingredients, are formulated to be given by various routes eg, oral, buccal, sublingual, rectal, parenteral, topical, inhalational. This process is more complex if the person takes other drugs and has other diseases, because drugdrug and drugdisease interactions are possible. List the major factors that affect drug absorption from oral and nonoral routes of drug administration. The systemic absorption of a drug is dependent on 1 the physicochemical. A drug substance is considered highly permeable when the extent of absorption in humans is determined to be 90 % or more of the administered dose based on a massbalance determination. The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug concentration gradient. A mechanistic approach to understanding the factors. The bioavailability of active drug can be varied from rapid and complete absorption to a slow, sustained rate of absorption or. Depending on the drug, toxicity may cause symptoms similar to a side effect or something more severe, including organ damageor a lifethreatening overdose. The following table highlights some of these other factors. The factors affecting absorption of drugs are related both to the drugs and to the body. It should be noted that these steps can also occur simultaneously during the dissolution process. Smaller particle sizes reduce internal diffusional and mass transfer limitation to the.
Describe various methods that may be used to study oral drug. Terms in this set 27 what are the 6 major factors affecting drug absorption related to the composition of the drug. Factors affecting drug absorption free download as powerpoint presentation. It also occurs by subcutaneous, intra muscular and transdermal routes of administration of drugs. For most drugs, the concentration at the site of the receptor determines the intensity of a drugs effect fig ure 14. The extent of absorption is linked to lipophilicity, and the partition coefficient between the nasal mucosa and any buffer solution used 4,35, allowing the drug to partition into the lipid cell membrane 36. Smt kishoritai bhoyar college of pharmacy, kamptee.
Knowledge of the adme process and the factors influencing drug absorption and. Factors affecting bioavailability global events usa. For assessing potential absorption behaviour of drugs from the gi tract, the following points may be useful. Drug absorption is determined by the drugs physicochemical properties, formulation, and route of administration. Many factors can affect a drug s absorption, distribution, metabolism, excretion, and ultimate effect. Factors affecting nasal absorption drug formulation design. Matrix technologies have often proven popular among the oral controlled drug delivery technologies because of their simplicity, ease in manufacturing, high level of reproducibility, stability of the raw materials and dosage form, and ease of scaleup and process validation. Certain changes within each of the four categories will produce uniform or predictable changes in drug. Basic pharmacokinetics sample chapter pharmaceutical press. Each route of drug application presents special biopharmaceutic consideration in designing a drug product. Physiologically, a drugs absorption is enhanced if there is a large surface area available for absorption e. Drug administration often the goal is to attain a therapeutic drug concentration in plasma from which drug enters the tissue therapeutic window between toxic concentration and minimal effective concentration. A mechanistic approach to understanding the factors affecting drug absorption.
Many factors can affect a drugs absorption, distribution, metabolism, excretion, and ultimate effect. Apr 27, 2016 introduction of absorption transport process factors affecting drug absorption with examples. Overview of response to drugs msd manual consumer version. Factors affecting surface drug absorption many factors affect how the application of a particular drug will be absorbed by the skin surface. Anatomical and physiological factors affecting drug absorption. However, the absorptive process does not occur during direct injection of drug by intravenous or intra arterial injection. Fig shows a loglog plot of solubilities of several drug vs their corresponding. Factors affecting drug metabolism drug metabolism metabolism. 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. Factors affecting drug absorption and distribution. A mechanistic approach to understanding the factors affecting. Factors affecting gastrointestinal absorption of drugs. Drug response can be affected by a wide range of factors, including genetics, age and certain environmental considerations. Other factors affecting drug absorption and distribution.
Adolescents in rural communities tend to use more alcohol and tobacco than other substances howard et al. Greater the lipid water solubility coefficient, more is the lipid solubility of the drug and greater is the absorption. The glucose is transported along with sodium from the git membrane. Consumption of food is one of the major factors affecting the gi system and. Laxatives and diarrhea, which speed up the passage of substances through the digestive tract, may reduce drug absorption. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Pdf overview of factors affecting oral drug absorption. Scribd is the worlds largest social reading and publishing site.
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. The action of a drug requires the presence of an adequate concentration of the drug in the fluid bathing the target tissue, and this, in turn, is determined by the dynamic relationship between absorption into the plasma following administration, the extent and rate of its distribution and the rate of. Physicochemical parameters affecting drug action posted jun 29, 2014, 10. Drugs and xenobiotics often are metabolized by several different phase i and phase ii pathways to give several metabolites. The factors affecting absorption of drugs are related both to the drugs and to the body factors related to drugs. A free powerpoint ppt presentation displayed as a flash slide show on id. There are many factors that can affect the absorption process of orally administered drugs. The action of a drug requires the presence of an adequate concentration of the drug in the fluid bathing the target tissue, and this, in turn, is determined by the dynamic relationship between absorption into the plasma following administration, the extent and rate of its distribution and the rate of inactivation by the body. Last updated on thu, 12 mar 2020 pharmaceutical chemistry.
A seminar on physicochemical properties affecting drug absorption. 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. Lipid water solubility coefficient is the ratio of dissolution of drug in lipid as compared to water. The relative amount of any particular metabolite is determined by the concentration and activity of the enzymes. Pdf this article provides an overview of variables that can affect drug absorption following oral administration in recent years, including both. One medication potentially can alter the effect of another, either reducing its effectiveness, making it toxic, or creating side effects. Drug particles can diffuse readily between the stomach and small intestine so that absorption is.
Drugs that are weak acids will pick up a proton when placed in an acidic environment and will, thus, be unionized. Because so many factors affect drug response, doctors must choose a drug appropriate for each person and must adjust the dose carefully. Factors affecting drug metabolism free download as powerpoint presentation. Qureshi, predicting absorption characteristics of drugs october 30, 2012 page 1 absorption mechanism of drugs from the gi tract. For example, blood pressure medication may need to be reduced with age to prevent blood pressure from going too low, which can present as dizziness or lightheadedness. Technological advancements in the area of matrix formulation have made controlledrelease product development. Food, other drugs, and digestive disorders can affect drug absorption and bioavailability. Pharm acy pharmaceuticaal technology srinivasa rao college of pharmacy visakhapatnam41 andhra pradesh 1 under the guidance of dr. Amount of drug that exists in unionized form and in ionized form is a function of pka of drug and ph of the fluid at the absorption site, and it can be determined by handersonhasselbach equation. A schematic diagram illustrating the processes involved in the dissolution of solid dosage forms is shown in fig. The absorption of lipophilic drugs is thought to occur via an alternative pathway to aqueous channels, namely the transcellular route. Contents introduction definition factors affecting absorption conclusion references 3.