Absorption is the process by which drugs enter the body. 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 online lecture lecturio. Thus making it difficult to determine its effects directly. How a drug works and what happens to it upon entering the body are important factors in drug design, in order to ensure optimal action in the desired amount of time. Aug 14, 2017 there are four factors that will influence the pharmacokinetic drugs test. Clinical pharmacokinetics is the application of pharmacokinetic principles to the safe and effective therapeutic management of drugs in an individual patient. List two physiologic factors that can alter each of the processes of absorption, distribution, and excretion.
Factors effecting on drug distribution ashok kari 1, gandhu sateesh, bharatha suresh, bodavula samba siva rao2 1. Many factors can affect a drug s absorption, distribution, metabolism, excretion, and ultimate effect. Genetic factors in drug metabolism american family physician. Factors affecting renal excretion of drugs include. If you continue browsing the site, you agree to the use of cookies on this website. A combination of metabolism and excretion constitutes drug elimination from the body.
There are four factors that will influence the pharmacokinetic drugs test. 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 the renal excretion of drugs hall, stephen d. Lipid soluble compound metabolized into more polar compound eliminated. Factors affecting the renal excretion of drugs stephen hall. The proposed research will attempt to remedy this shortcoming by quantitating the effect of changes in renal blood flow, drug protein binding, drug concentration, aging, and several experimental disease states upon the renal clearance of model substrates in an isolated perfused rat kidney preparation iprk. The effect of chronic renal failure on drug metabolism 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. Impaired renal function may lead to a clinically significant accumulation of drugs eliminated by the kidneys, if more than 50% of the dose is normally excreted unchanged in the urine and the renal function is less than 50% of the normal value. In elderly patients, or those with chronic renal disease see the record on renal disorders including interstitial nephritis, glomerulonephritis, hypertensive nephrosclerosis, diabetic nephropathy, and polycystic kidney disease, renal function becomes progressively reduced such that drug excretion may. Absorption can be facilitated by heat, massage or vasodilators. The use of mathematical principles and methods to explain the plasma concentration with time changes in a discipline. Transdermal administration, drug testing and analysis, 10, 5, 821831, 2017. Only relatively polar drugs are excreted in appreciable amounts by the kidneys.
Introduction to pharmacokinetics and pharmacodynamics. In elderly patients, or those with chronic renal disease see the record on renal disorders including interstitial nephritis, glomerulonephritis, hypertensive nephrosclerosis, diabetic nephropathy, and polycystic kidney disease, renal function becomes progressively reduced such that drug excretion may become impaired. Distribution, metabolism and excretion are sometimes referred to collectively as drug disposition. Many factors affect the rate and pathway of metabolism of drugs, and the major influences can be subdivided into internal physiological and pathological and.
Pdf overview of factors affecting oral drug absorption. The speed with which drugs move in and out of the body varies widely among different people. A drug, which is either biologically active itself or a prodrug, may be excreted in its original chemical state. Indiana universitypurdue university at indianapolis, indianapolis, in, united states. Some drugs are irritating and should be administered with meals to reduce adverse effects.
Factors affecting urinary excretion of testosterone metabolites conjugated with cysteine andreu fabregat bioanalysis research group, imim, hospital del mar, 08003 barcelona, spain. These factors may affect how the body absorbs the drug, how the body breaks down metabolizes and eliminates the drug, or what effects the drug has on the body. Overview of pharmacokinetics clinical pharmacology. Greater the lipid water solubility coefficient, more is the lipid solubility of the drug and greater is the absorption. The urinary excretion of both compounds was unrelated to age, sex, urinary volume, or creatinine, nor was any consistent diurnal. Pharmacokinetics definition, principles, factors affecting. Factors governing the extent of drug absorbed from the mucosal surface include the concentration the active ingredient, the vehicle used for its delivery, contact time with the mucosal surface. Factors affecting drug activity flashcards quizlet. Feb 27, 2019 drug distribution is a subject that is covered in a branch of pharmacology called pharmacokinetics. Laboratory of chemical pharmacology, national heart and lung institute, national institutes of health bethesda, md. Examples of genes affecting chd include the cholesteryl ester. Factors affecting pharmacokinetics of drugs medicilon inc. Overview of pharmacokinetics clinical pharmacology merck. The renal excretion of drugs is mainly controlled by three factors.
Or excretion is defined as the process where by drugs or metabolites are irreversibly transferred from internal to external environment through renal or non renal route. Factors affecting urinary excretion of testosterone metabolites conjugated with cysteine. Factors contributing to variability in drug pharmacokinetics. Excretion drug excretion is defined as the removal of drugs from the body.
It can be slowed by coadministration of vasoconstrictors, a practice commonly used to prolong the local action of local anesthetics. Factors affecting drug absorption and distribution request pdf. Excretion of unchanged or intact drug is needed in termination of its pharmacological action. Feb 27, 2019 various factors can affect renal excretion, such as. Dhanvanthari institute of pharmaceutical sciences, kothagudem, khammam. Given by any route other than intravenously, drug molecules must cross tissue membranes e. Excretion the interrelationship between drug distribution, biotransformation and excretion and the drug in figure 1. Explain how bioavailability can impact drug response and product selection. The following factors can affect the blood concentrations of a drug. Toxicants are removed in the kidney by glomerular filtration, tubular excretion by passive diffusion, and active tubular secretion. Lipid water solubility coefficient is the ratio of dissolution of drug in lipid as compared to water. Overview of response to drugs msd manual consumer version. Genetic and environmental factors affecting drug disposition.
Drugrelated factors affecting pharmacokinetics the physicochemical properties of a drug, including its solubility and permea bility, affect its absorption. Pharmacokinetic is a quantitative study of drugs in the body absorption, distribution, metabolism and excretion of the law. Clinical pharmacokinetics pharmacology education project. Unionized drugs and metabolites are usually able to diffuse out of the renal tubule and are reabsorbed into the blood. Absorption, distribution, metabolism, and excretion. Many factors affect the rate and pathway of metabolism of drugs, and the major influences can be subdivided into internal physiological and pathological and external exogenous factors as.
Membrane structure and function the cell membrane is a semipermeable lipoid sieve containing numerous aqueous channels, as well as a variety of specialized carrier molecules. Factors influencing drug response intrinsic genetic. 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. Intravenous administration does not involve absorption and, hence, there is no loss of drug. Acidification of urine increases reabsorption and decreases excretion of weak acids, and, in contrast, decreases reabsorption of weak bases. Inhalation volatile anesthetics, as well as many drugs which affect pulmonary function, are administered as aerosols. Additional factors affecting drug reabsorption include lipid solubility, drug size, and urine flow.
Possible factors affecting this stage include the rate of blood flow perfusion to the tissue, the tissue mass itself, and vascular and tissue membrane permeability. Pharmacodynamics, described as what a drug does to the body, involves receptor binding, postreceptor effects, and. 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. Factors affecting distribution of drug tissue permeability of drug 1. Factors affecting the urinary excretion of endogenously. Factors effecting bioavailability studies bodavula samba siva rao department of pharmacy, khammam college of pharmacy, khammam, andhra pradesh the goal of most oral dosage forms is to serve as a vehicle for the delivery of drugs to the blood stream for distribution to the site of action. Physiological factors affecting absorption pharmatutor.
Drugs that are bound to large proteins in the plasma cannot be filtered out of the plasma, and hence remain in the blood circulation. If we need to understand the basics we must be aware of the fact that drug effect in the body cannot be directly measured for e. Species differences have a major influence on the renal excretion of ionized drugs. Ultimately, the expression of an enzyme, and therefore, the responses to drugs that it metabolizes will be an integration of all the nongenetic factors that can control the enzyme impinged upon the individuals genetic constitution. Factors affecting drug absorption and distribution. Limits gf but doesnt limit active tubular secretion 3. Clinical pharmacokinetics is the application of pharmacokinetic principles to the safe and effective therapeutic management of drugs in. Pharmacokinetics, sometimes described as what the body does to a drug, refers to the movement of drug into, through, and out of the bodythe time course of its absorption, bioavailability, distribution, metabolism, and excretion. Factors affecting urinary excretion of testosterone. With oral administration, several factors affect the absorption of a drug.
Additional factors affecting drug reabsorption include lipid solubility, drug size, and. 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. Drug excretion is the process of eliminating a drug from the body. Clinical pharmacokinetics is the application of pharmacokinetic principles to. Alternatively, all or a portion of a drug may undergo chemical modification and be eliminated as biologically active, or inactive, metabolites see the record on drug biotransformation. Compare the roles of passive diffusion and carriermediated transport in. Impaired renal function may lead to a clinically significant accumulation of drugs eliminated by the kidneys, if more than 50% of the dose is normally excreted unchanged in the urine and the renal function is less than 50% of the.
Drugs are absorbed from the site of administration into the systemic circulation, where they may interact with the proteins. Many factors can affect a drugs absorption, distribution, metabolism, excretion, and ultimate effect. Factors affecting renal drug excretion glomerular filtration o drugs enter the kidney from the renal artery o glomerulus can be thought of as a spaghetti strainer spaghetti proteins is not filtered, whereas salt added to the spaghetti small molecules such as drugs or different ions are filtered. Excretion of drugs excretion is defined as the process where by drugs or metabolites are irreversibly transferred from internal to external environment through renal or non renal route. The drug distribution is usually varied, and depends on several factors such as. Drug absorption, drug distribution, drug dissolution, drug solubility introduction. For most tissues, passive aqueous diffusion through channels.
Pharmaceutical factors a chemical factors b physicochemical properties of drug substances 1. The factors affecting absorption of drugs are related both to the drugs and to the body. Various factors can affect renal excretion, such as. This method is very effective if the drug is excreted in the unchanged form.