Drug molecules with very low aqueous solubility often have lower bioavailability because of the limited amount of dissolved drug at the site of absorption. The invivo bioavailability of a drug product is demonstrated by the rate and extent of drug absorption, as determined by comparison of measured. The other major factor which determines the rate of drug distribution is blood perfusion. Some basic thermodynamic concepts will be introduced, particularly that of thermodynamic activity, an important parameter in determining drug potency. Phar 7633 chapter 12 physicalchemical factors affecting oral. For instance,a drug administered orally in tablet or capsule form it has to undergo disintegration and deaggregation rapidly.
However, many drugs are given in solid dosage forms and therefore must dissolve before absorption can take place. Long intestinal transit time is desirable for complete absorption of drug e. Blood perfusion rate the rate at which blood perfuses to different organs varies widely. Absorption ionisation in man, stomach is ph 2 and small intestine ph 6 weak acids unionised form is more prevalent in the stomach. With this book as their guide, readers have access to all the current information needed to thoroughly investigate and accurately determine a compounds pharmaceutical properties and their effects on drug absorption. Physicochemical factors affecting absorption authorstream presentation. Genetic and environmental factors affecting host response to drugs. Factors affecting gastrointestinal absorption of levothyroxine. The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug concentration gradient. Effect of certain formulation factors on the dissolution and. Factors affecting dissolution rate divided into five classes a. In each region, the absorption rate increased with the drug lipophilicity. Pharmaceutical factors a chemical factors b physicochemical properties.
Smt kishoritai bhoyar college of pharmacy, kamptee. 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. In the previous chapter, it has been shown how physiological and pathological factors can affect drug metabolism and how these factors vary in importance. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Physiologic factors related to drug absorption applied. The oral absorption of any chemical entity reflects a complex spectrum of events. Overview of factors affecting oral drug absorption naining song a,b, shaoyu zhang b, changxiao liu a a tianjin state key laboratory of pharmacokinetics and pharmacodynamics, tianjin institute of. Physicochemical factors affecting skin absorption request pdf.
In this chapter we examine some of the important physicochemical properties of drugs in aqueous solution which are of relevance to such liquid dosage forms as injections, solutions, and eye drops. Clinically relevant drug interactions are indicated as c, d, and x. Although some absorption of acids takes place in the stomach, absorption also occurs in small intestine due to. When the standard consists of intravenously administered drug, this is known as relative bioavailability. Factors related to the physicochemical properties of the drug.
Mar 10, 2020 steric factors determined by the stereochemistry of the receptor site surface and that of the drug molecules are, therefore, of primary importance in determining the nature and the efficiency of the drug receptor interaction. Membrane permeability tends to restrict the transfer and distribution of drugs once they are delivered to the tissue. Pdf overview of factors affecting oral drug absorption. The safety profile of the ingredients used in topical dosage forms and its evaluation is an issue of utmost importance. Nov 02, 2017 this feature is not available right now. The following factors are commonly reported as significantly influencing the extent of nasal absorption. Properties pdf win32 programming is required to give optimal absorption. Topics on drug metabolism 2 bioavailability humans. A suitable equilibrium between safety and efficacy is crucial before. Physicochemical properties effect on absorption of drugs. A mechanistic approach to understanding the factors affecting. The absorption rates of the acylsalicylic acids were different in the intestinal regions. 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 nasal absorption drug formulation design. There are, however, factors outside the body that can also have a profound influence on drug metabolism. Physiological factors affecting drug toxicity sciencedirect. But it depends on the amount of carriers by which the drug molecules can be bound.
Physicochemical factors of drugs affecting absorption, distribution, and excretion. A mechanistic approach to understanding the factors affecting drug. The glucose is transported along with sodium from the git membrane. Describe various methods that may be used to study oral drug. Qureshi, predicting absorption characteristics of drugs october 30, 2012 page 1 absorption mechanism of drugs from the gi tract. The influence of physicochemical properties on adme. Apr 27, 2016 introduction of absorption transport process factors affecting drug absorption with examples. In general, drugs with lower than 10 mgml in aqueous solutions are expected to. The book emphasizes oral absorption, explaining all the physicochemical methods used today to analyze drug candidates. However, it was shown that the absorption rates in the small intestine tended to reach a ceiling at the high lipophilicity.
Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. A mechanistic approach to understanding the factors affecting drug absorption. Wafik gouda the rate of absorption of poorly soluble drugs is dissolution ratelimited. List the major factors that affect drug absorption from oral and nonoral routes of drug administration. Physicochemical characters affecting absorption physical properties that are due to shape, size and physical form of any drug molecule, usually unaffected by chemical changes, affect the bioavailability of therapeutic moieties. 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. Apr 15, 2020 a combination of the structure and function of the nasal mucosa as a barrier to absorption, the properties of the active drug and the formulation within which it is contained will affect the extent to which a compound is absorbed nasally. Othe af90t is a fully automatic capsulefilling machine that can fill a large variety of powder formulations into hard gelatin capsules.
Regulatory toxicology and pharmacology 3, 389398 1983 physiological factors affecting drug toxicity keith bailey bureau of drug research, health protection branch, tunneys pasture, ottawa, ontario kia ol2, canada received july b, 1983 physiological factors that affect the fate of drugs in the body and thereby have effects on their pharmacology and toxicology involve the systems that. The rate and extent of absorption of a drug depend on the effective concentration of that drug, i. Jun 25, 2019 the solubility enhancement of a drug substance by salt formation is related to several factors including the thermodynamically favored aqueous solvation of cations or anions used to create the salt of the active moiety, the differing energies of the salt crystal lattice, and the ability of the salt to alter the resultant ph. Solubility as shown with equation 1, the prerequisite for good oral drug absorption is ensuring a sufficient compound amount is in solution at the primary site of absorption. Physicochemical characters affecting absorption physical. Physicochemical parameters affecting drug action dr. Peristaltic contraction promotes drug absorption by increasing the drug membrane contact and by enhancing dissolution especially of poorly soluble drugs. Physicalchemical factors affecting oral absorption drug dissolution so far we have looked at the transfer of drugs in solution in the gi tract, through a membrane, into solution in the blood. Factors affecting drug absorption and distribution.
For assessing potential absorption behaviour of drugs from the gi tract, the following points may be useful. Concepts and theoretical calculations of oral bioavailability bioavailability f is the extent to which an active moiety is absorbed from a pharmaceutical. 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. Bioavailability physicochemical and dosage form factors. Consumption of food is one of the major factors affecting the gi system and. Pharmaceutical factors a chemical factors b physicochemical properties of drug substances 1. With the possible exception of the general anesthetics, such drugs must possess a high structural specificity to. Direct and indirect methods may be used to assess drug bioavailability. Pathological and physiological factors affecting drug.
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