Factors affecting drug absorption and distribution. Some disorders like diabetic neuropathy causes gastric stasis and decrease the drug absorption. Factors which influence gastrointestinal drug absorption. In general, children require smaller doses than adults. Factors affecting gastrointestinal absorption of drugs. Interactions that alter absorption with food or nutrient can be avoided by separating the administration of drugs and food intake by about 2 hours. 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. Factors affecting drug absorption and distribution sciencedirect. What are the 6 major factors affecting drug absorption related to the composition of the drug. This article throws light upon the eight main physiological factors that affect the rate of drug absorption.
However, other factors affect drug response as well. A mechanistic approach to understanding the factors affecting. Two factors that can produce drug interactions are modulation of absorption distribution and metabolism driven by the combined activity of drug transporters and metabolizing enzymes. Factors affecting pharmacokinetics of drugs medicilon inc. Factors affecting renal excretion of drugs include. Pdf overview of factors affecting oral drug absorption. Any change, like crushing tablets, that may affect the rate of absorption, metabolism or. Pharmaceutic factors affecting drug bioavailability. Solubility of drug plays a prime role in controlling its dissolution from dosage form. Factors affecting drug absorption linkedin slideshare. Solubility and permeability are considered as the major physicochemical factor that affect the rate and extent of oral drug absorption, moreover other. A drug is transported across the biological membrane by several methods, of which passive diffusion is the most important. Physiologic factors related to drug absorption applied.
Factors affecting drug absorption and distribution anaesthesia and. Physiological factors affecting oral absorption objective. 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. Absorption of drugs is dependent on numerous factors that vary depending on the route of administration. Physiological factors and drug absorption pharmacokinetics. In general drug absorption, distribution in the body, activity, metabolism and excretion can all change as a result of ageing. Formulation sublingually given drugs are rapidly absorbed. Unintentional alterations in either the rate or amount of drug absorption can lead to ineffective oral therapy on the one hand, or toxic reactions on the other. Physiological factors affecting drug absorption rate of gastric emptying is a major determinant of initial delay in drug absorption. View the article pdf and any associated supplements and figures for a period of 48 hours. Many drugs will bind strongly to proteins in the blood or to food substances in the gut. Considering the structure of membranes transport processes b. Introduction to pharmacokinetics and pharmacodynamics.
Intestinal motility is a determinant of the extent of drug absorption. Each route of drug application presents special biopharmaceutic consideration in designing a drug product. Pdf formulation considerations and factors affecting. Either youngs formula based on age or clarks formula based on weight can be used for calculating the doses for children but the formula based on body surface area is more reliable. What are the factors affecting the dose and action of drugs. Definitions pharmacokinetics oevaluate the way in which a drug interacts with various barriers within a biological system pharmacodynamics ostudy of the relationship between systemic exposure of a drug and its biological effects on tissue oabsorption can be defined as the movement of active drug or prodrug from the site of administration across biologic. Factors affecting absorption of a drug from its dosage form.
After reading this article you will learn about the pharmaceutic factors affecting drug bioavailability. Physiological factors influencing oral drug absorption. 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. For most drugs, the concentration at the site of the receptor determines the intensity of a drug s effect figure 14. Drug absorption involves the movement of the drug from its injectionadministration site into the systemic circulation. Factors influencing product bioavailability include drug sol ubility. Impact of physiological, physicochemical and biopharmaceutical factors in absorption and metabolism mechanisms on the drug oral bioavailability of rats and humans. Pathological and physiological factors affecting drug absorption, distribution. Pathological and physiological factors affecting drug.
Physiological factors affecting absorption pharmatutor. Influence of food and diet on gastrointestinal drug absorption. Lipid water solubility coefficient is the ratio of dissolution of drug in lipid as compared to water. Drug absorption, drug distribution, drug dissolution, drug solubility introduction. The bioavailability of active drug can be varied from rapid and complete absorption to a slow, sustained rate of absorption or. To understand the physiological factors which affect the oral absorption of drug products physiological factors. Physiologically, a drug s absorption is enhanced if there is a large surface area available for absorption e. Reactions between components of pdf itself or between components and cover of container. Pharmacists must also understand the relationship of drug dosage to therapeutic efficacy. The excessively rapid movement of git impairs absorption. Some disorders like diabetic neuropathy causes gastric stasis. Factors affecting drug absorption small intestine stomach. Drug absorption from pulmonary epithelia occurs only after inhaled drug deposits in the lung and undeposited aerosolized particles clear out of the lung in expired air.
The chemical nature of a drug has little influence on its bulk transfer in the blood stream. 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. 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. Drug absorption and distribution inhibition of transporters can affect drug absorption andor distribution to different sites. Solubility and permeability are considered as the major physicochemical factor that affect the rate and extent of oral drug absorption, moreover other physicochemical properties always show their. Drug absorption depends on the lipid solubility of the drug, its formulation and the route of administration. Other factors that also impact drug absorption include the following.
The following are the factors which affect the adsorption, 1 nature of the adsorbate gas and adsorbent solid i in general, easily liquefiable gases e. Absorption is a primary focus in drug development and medicinal chemistry, since the drug must be absorbed before any medicinal effects can take place. Journal of pharmacokinetics and biopharmaceutics 5. 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. Depending on the situation, drugs are administered via different routes. Minimum aqueous solubility of 1% is required to avoid potential solubility limited absorption problems. Pharmaceutical factors a chemical factors b physicochemical properties of drug substances 1. 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. Factors which affect extent of adsorption, chemistry study. However, most drugs have to cross membranes to exert their.
Depending upon the type of inhalation technology, only about 2050% of the pulmonarydelivered dose is deposited in the. Moreover, the drugs pharmacokinetic profile can be easily and significantly changed by adjusting factors that affect absorption. Factors affecting drug absorption free download as powerpoint presentation. Drug absorption is defined as the process of movement of unchanged drug from the site of administration to systemic circulation. Pharmacokinetics in older patients rosemont pharma. The pharmacokinetic properties of a drug comprise the relationship between its absorption, distribution and inactivation. Large interindividual variations in drug response can arise from multiple genetic and environmental factors affecting drug absorption, distribution, biotransformation, excretion, interaction. Binding to plasma proteins will increase the rate of passive absorption by maintaining the concentration gradient of free drug.
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