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. Polarity the introduction of polar groups can increase water solubility, crystal form the impact of drug bioavailability is more and more attention, the melting point of the solubility, thus affecting the absorption of drugs, affecting bioavailability. Factors affecting drug absorption linkedin slideshare. The rectum is an interesting area for drug absorption because it is not buffered and has a neutral ph. For example, highfiber foods and calcium supplements may bind with a drug and prevent it from being absorbed. Describe firstorder, onecompartment pharmacokinetics and calculate kinetic parameters.
This article throws light upon the eight main physiological factors that affect the rate of drug absorption. This commentary will discuss barriers to sc absorption as well as physiological and experimental factors that could affect pharmacokinetics of subcutaneously administered large protein therapeutics in preclinical models. Influence of food and diet on gastrointestinal drug. Observed effects of food on drug absorption are the net result of various factors. The distribution and rate of equilibration across the placenta is determined by placental blood flow and the free drug concentration gradient. Dapsone, itraconazole, and ketoconazole may also be less well absorbed in the presence of. Drug absorption, drug distribution, drug dissolution, drug solubility introduction. Factors affecting the absorption of subcutaneously. When the salt of a weak acid dissolves in the stomach, it generates a diffusion layer of relatively high ph which,in turn, promotes. Salt forms of these drugs cannot be prepared because the free base readily precipitates out due to the weak basicity. Lipid water solubility coefficient is the ratio of dissolution of drug in lipid as compared to water. Anatomical, physiological and experimental factors. Factors affecting absorption of a drug from its dosage form.
Write in brief about factors affecting drug absorption. Factors influencing product bioavailability include drug solubility, permeability, and the rate of in vivo dissolution. The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug. Many drugs will bind strongly to proteins in the blood or to food substances in the gut. Factors affecting drug absorption and distribution. Invitro dissolution testing or drug release testing may be used for seeking waiver of required product to conduct invivo bioavailability or bioequivalence studies. Pharmacokinetic part 01 absorption and factors affecting absorption of drugs hindi solution pharmacy. Describe two types of drug interaction and explain how. Anatomical, physiological and experimental factors affecting the bioavailability of sc administered large biotherapeutics. Learn vocabulary, terms, and more with flashcards, games, and other study tools.
The mechanisms of food effect and their consequences can involve multiple factors, including human postprandial physiology, properties of the drug, and how the drug is administered. Bound drug unbound drug clearance free tissue drug concentrations active. Moreover, the drug s pharmacokinetic profile can be easily and significantly changed by adjusting factors that affect absorption. In this regard, the biopharmaceutics classification system has proven to be an important tool for predicting compounds likely to be associated with bioavailability problems. The use of mathematical principles and methods to explain the plasma concentration with time changes in a discipline.
Factors affecting drug absorption free download as powerpoint presentation. The factors affecting absorption of drugs are related both to the drugs and to the body. Scribd is the worlds largest social reading and publishing site. Explain how bioavailability can impact drug response and product selection. Since this variability is largely influenced by the absorption of insulin, a deeper understanding of the factors affecting the absorption of insulin from the subcutaneous tissue is necessary in order to. Intestinal transporters play an important role in drug absorption. Factors affecting absorption of drug pharmacokinetics. Summarize the impact of gestational age, postnatal age, and disease state on drug absorption, distribution, metabolism, and elimination. A mechanistic approach to understanding the factors affecting drug absorption. Factors affecting drug metabolism online lecture lecturio. After completing this article, readers should be able to. Factors affecting drug absorption flashcards quizlet.
Major process for absorption of more than 90% of drugs. Oral administration of a drug with food generally reduces its absorption. Poor bioavailability and poor scalability from preclinical models are often cited. Drugs such as neostigmine and gentamicin, which are highly ionised, are poorly absorbed. Exogenous factors influencing insulin absorption are summarized in table 2. The oral absorption of any chemical entity reflects a complex spectrum of events. Pharmacological and pathophysiological role of histamine and releasers of histamine and betahistine drug what is epg pathshala, eadhyayan, ugc moocs and epathya pharmacokinetic. In most cases, the absorption of drugs from the gastrointestinal tract is reduced or delayed by food. In addition to delaying insulin absorption by decreasing the surfacetovolume ratio, larger injection volumes may also exert a depressive effect on the microcirculation due to an increase in interstitial fluid pressure, thus further delaying absorption 110. Compare the roles of passive diffusion and carriermediated transport in drug absorption. There are four factors that will influence the pharmacokinetic drugs test. Aug 14, 2017 therefore, the drug is required to have certain water solubility.
Factors affecting drug absorption and distribution sciencedirect. List two physiologic factors that can alter each of the processes of absorption, distribution, and excretion. Pdf this article provides an overview of variables that can affect drug absorption following oral administration in recent. Factors which influence gastrointestinal drug absorption deranged. The systemic absorption of a drug is dependent on 1 the physicochemical. Clinical pharmacokinetics is the application of pharmacokinetic principles to the safe and effective therapeutic management of drugs in. This chapter answers parts from section bii of the 2017 cicm primary syllabus, which expects the exam candidate to describe absorption. Factors affecting drug absorption pharmaquest home pages. For many drugs, the gastrointestinal absorption rate, but not the extent of absorption, is reduced by the presence of food in the. Pharmaceutical factors a chemical factors b physicochemical properties. Food, other drugs, and digestive disorders can affect drug absorption and bioavailability.
The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug concentration gradient. Drug absorption drugs merck manuals consumer version. The following factors can affect the blood concentrations of a drug. Write in detail about the factors that are related to the physiological conditions and formulation of dosage form. Anatomical, physiological and experimental factors affecting. Pharmacokinetic part 01 absorption and factors affecting. Other factors that also impact drug absorption include the following.
Factors influencing product bioavailability include drug solubility. Pdf overview of factors affecting oral drug absorption. Physiological factors and drug absorption pharmacokinetics. Neonatal pharmacology and pharmacokinetics american academy. Metoclopramide is a drug that stimulates stomach contraction, relaxes the pyloric sphincter, and, in general, increases intestinal peristalsis, which may reduce the effective time for the absorption of some drugs and thereby reduce the peak drug concentration and the time to reach peak drug concentration. A mechanistic approach to understanding the factors. Physiologically, a drugs absorption is enhanced if there is a large surface area available for absorption e. Pdf factors affecting intraocular bioavailability of drugs. 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. Nov 01, 2002 after completing this article, readers should be able to. The pharmacokinetic properties of a drug comprise the relationship between its absorption, distribution and inactivation. Factors affecting pharmacokinetics of drugs medicilon inc. 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. Absorption, factors affecting absorption includes route of administration, bioavailability and bioequivalence.
In rectal absorption both low and high molecule weight compounds in a constant ratio of absorption. Neonatal pharmacology and pharmacokinetics american. Pharmacists must also understand the relationship of drug dosage to therapeutic efficacy. 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. Introduction to pharmacokinetics and pharmacodynamics. There are many factors that can affect the absorption process of orally administered drugs. Factors that increase gastric emptying will usually increase the rate of absorption of a drug. However, some drugs are unaffected by food, while the absorption of a small number of drugs is increased. Patient related factors affecting on drug absorption, drug absorption, absorption, factors affecting, patient related factors. A mechanistic approach to understanding the factors affecting. 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. The factors affecting absorption of drugs are related both to the drugs and to the body factors related to drugs.
Food effect, also known as fooddrug interactions, is a common phenomenon associated with orally administered medications and can be defined as changes in absorption rate or absorption extent. Pharmaceutical factors a chemical factors b physicochemical properties of drug substances 1. 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. Factors affecting absorption of drug pharmacokinetics medicos scientia. When the salt of a weak acid dissolves in the stomach, it generates a diffusion layer of relatively high ph which,in turn, promotes further.
Absorption is a primary focus in drug development and medicinal chemistry, since the drug must be absorbed before any medicinal effects can take place. For many drugs, the gastrointestinal absorption rate, but not the extent of absorption, is reduced by the presence of food in the gut. Physiochemical factors affecting drug absorption free download as powerpoint presentation. The crystalline form requires a higher amount of energy to free a molecule of. 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. 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. Factors affecting drug absorption authorstream presentation.
Greater the lipid water solubility coefficient, more is the lipid solubility of the drug and greater is the absorption. Necrosis, type of necrosis, oxygen derived free radicle, antioxidant histamine. Factors influencing product bioavailability include drug sol ubility, permeability, and the. Moreover, the drugs pharmacokinetic profile can be easily and significantly changed by adjusting factors that affect absorption. Laxatives and diarrhea, which speed up the passage of substances through the digestive tract, may reduce drug absorption. Factors affecting surface drug absorption many factors affect how the application of a particular drug will be absorbed by the skin surface.
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. Georgetown university, has developed a free database summarizing. Variability in the effect of subcutaneously administered insulin represents a major challenge in insulin therapy where precise dosing is required in order to achieve targeted glucose levels. Trafficking the drug effectively through the lymphatic may alleviate the load on uptake transporters and enhance overall bioavailability of injected therapeutic proteins.1267 1293 575 937 45 86 95 447 168 205 1274 407 873 1377 1417 1231 1536 1570 1151 1007 156 591 1220 1410 891 979 903 905 194 680 1601 1353 1045 108 170 470 1277 593 1394 1489 634 108 963 1427 83