Factors affecting distribution of drugs include those related to the drug and those related to the body. Her work has appeared in metroparent magazine, anew heart. Get a printable copy pdf file of the complete article 2. Drugs given orally will generally be absorbed by the gastrointestinal tract. Distribution in pharmacology is a branch of pharmacokinetics which describes the reversible transfer of a drug from one location to another within the body once a drug enters into systemic circulation by absorption or direct administration, it must be distributed into interstitial and intracellular fluids. Effects of the investigational drug on the pharmacokinetics of other drugs. Clinical pharmacokinetics is the application of pharmacokinetic principles to the safe and effective therapeutic management of drugs in an individual patient. Physiological factors and drug absorption pharmacokinetics.
Drug distribution throughout the body occurs primarily via the circulatory system, which consists of a series of blood vessels that carry the drug in the blood. Determine drug protein binding constants using in vitro methods. The absorption, distribution, metabolism and excretion of. Due to this decline in organ function, drug absorption, distribution, metabolism and excretion adme processes in elderly people are worse than those of young people.
Factors affecting drug distribution through infusion by the infusion physics study group 051809 convection enhanced delivery ced is a technique used to distribute drugs inside the brain parenchyma using pressure to cause the movement of infused fluid. Factors effecting on drug distribution ashok kari 1, gandhu sateesh, bharatha suresh. In 2006 she began channeling her knowledge into healthrelated articles for print and online publications. Differences in drug distribution among the tissue essentially arise as result of a number of factors. 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. Other factors affecting drug absorption and distribution. Older people, even when thin, may store large amounts of fatsoluble drugs because the proportion of body fat increases with age. 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. Agerelated changes in the kidneys, liver, and other organs will influence the way many medications work. Drug distribution, metabolism, and excretion slower. After a drug has entered tissues, drug distribution to the interstitial fluid is determined primarily by perfusion.
Likewise, plasma levels will depend on dosage, time and route of drug administration, the bioavailability of the drug and time of blood sampling. Drug distribution drugs msd manual consumer version. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Binding to tissues also affects drug concentrations in the bloodplasma and. Greater the lipid water solubility coefficient, more is the lipid solubility of the drug and greater is the absorption. In general, because of a loss of muscle mass, elderly persons are physically smaller. Factors affecting distribution of drug tissue permeability of drug 1.
Explain how manipulation of these factors can increase toxicity. Developmental pharmacokinetics in pediatric populations. For poorly perfused tissues eg, muscle, fat, distribution is very slow, especially if the tissue has a high affinity for the drug. For instance, obese people may store large amounts of fatsoluble drugs, whereas very thin people may store relatively little. Drug distribution to tissues clinical pharmacology msd manual. Physiological properties of drug pka, lipid solubility, etc. Interaction, guideline, metabolism, inhibition, induction, transport. 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. Greater the lipid solubility, more is the distribution and vice versa. Pharmacokinetics in older patients rosemont pharma. Transfer of drugs from bloodstream to tissues around the body.
Table 1 lists the extent of plasma protein binding of selected drugs. Factors affecting drug metabolism free download as powerpoint presentation. The following table highlights some of these other factors. Drug metabolism and pharmacokinetics in malnutrition. Pharmacological action of drug depends upon its concentration at the site of action thus distribution plays important role in onset of action intensity of action duration. Therapeutic response and toxicity are therefore likely to be altered. Lipid water solubility coefficient is the ratio of dissolution of drug in lipid as compared to water. Responding to these risks before they become problems can be difficult. Drug distribution to tissues clinical pharmacology. Morgan on general factors affecting drug metabolism. Introduction to pharmacokinetics and pharmacodynamics ashp. As you learned in study session 5, the incidence of malaria varies from place to place and at different times. Guideline on the investigation of drug interactions european. Explain how volume of distribution, drug clearance, and halflife can be affected by protein binding.
Chapter objectives list physiological factors that influence drugs and may lead to an. Factors affecting dissolution rate divided into five classes a. Drug distribution across the placenta is a special case and considered separately. Factors affecting drug distribution through infusion.
In addition, absorption, distribution, metabolism, excretion and concurrent drug administration may profoundly affect plasma drug concentrations. Data obtained show that the doses and dosage regime in the undernourished or malnourished depend on three factors, namely environment, patient and the drug concerned. Pathological and physiological factors affecting drug. Low molecular weight drugs pass through by simple diffusion. D associate professor department of pharmaceutics, sharadchandra pawar college of pharmacy, pune, maharashtra, india 2. Once a toxicant has been absorbed through any of the body systems, it can then move throughout the body systemically by the circulatory system or on a cellular level by different transport mechanisms. Clinical pharmacokinetics is the application of pharmacokinetic principles to the safe and effective therapeutic management.
Drug distribution in special compartments and bioavailability. Describe how drug distribution can affect the apparent volume of distribution. Distribution is generally uneven because of differences in blood perfusion, tissue. Nutritional status, multiple chronic diseases, and functional and cognitive deficits are other agerelated factors that may have an impact on drug therapy. Factors that affect malaria transmission study session 6 factors that affect malaria transmission introduction. 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. Furthermore, drug sensitivity is different in the elderly, who are prone to have adverse reactions to drugs.
This article throws light upon the eight main physiological factors that affect the rate of drug absorption. If possible, the data files used in the simulation preferably including drug. Clinical pharmacokinetics is the application of pharmacokinetic principles to the safe. After a drug enters the systemic circulation, it is distributed to the bodys tissues. Evaluate the impact of change in drug protein binding or displacement on free drug concentration. Introduction to pharmacokinetics and pharmacodynamics. Generally, the bioavailability of oral drugs follows the order. Maternal factors dose and duration of therapy low dose, infrequent dosing, short duration if drug contraindicated, may consider pump and dump route of administration drugs given iv before of poor po bioavailability are usually poorly absorbed by infant through milk drug pharmacokinetics. Definition drug distribution is defined as the reversible transfer of drug between one compartment blood to another extra vascular tissue 5.
The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug concentration gradient. Effects of cellular pharmacology on drug distribution in tissues. Factors affecting drug absorption and distribution. 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. Developmental factors affecting drug pharmacokinetics in neonates and infants.
The factors that influence the tissue distribution of such drugs include drug transport. While drug prevention and treatment have traditionally focused on changing individual behaviours, such efforts can have only limited impact when changes are not made to the environment, that is, to the social determinants of drug use. The factors affecting absorption of drugs are related both to the drugs and to the body. A healthcare professional for more than 10 years, rica lewis has obtained numerous certifications in the industry. 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. A variety of factors contribute to drug use and other problem outcomes, both individual and environmental. For compounds with molecular diameter above 100 a transfer is slow. Distribution of a drug is not uniform throughout the body because different tissues receive the drug from plasma at different rates and to different extents. In this paper, the agerelated changes in drug absorption, 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. Developmental pharmacokinetics in pediatric populations ncbi. Distribution of a drug may also vary from person to person.
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