Factors affecting the absorption of subcutaneously. 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. Pharmacists must also understand the relationship of drug dosage to therapeutic efficacy. Physiological factors and drug absorption pharmacokinetics. After completing this article, readers should be able to. Pharmaceutical factors a chemical factors b physicochemical properties. The distribution and rate of equilibration across the placenta is determined by placental blood flow and the free drug concentration gradient. Factors affecting absorption of drug pharmacokinetics medicos scientia. Pharmacokinetic part 01 absorption and factors affecting absorption of drugs hindi solution pharmacy. Explain how bioavailability can impact drug response and product selection.
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. 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. Factors affecting drug absorption pharmaquest home pages. Major process for absorption of more than 90% of drugs. Aug 14, 2017 therefore, the drug is required to have certain water solubility. A mechanistic approach to understanding the factors affecting. Factors affecting drug absorption and distribution. Factors affecting absorption of drug pharmacokinetics. 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. Drugs such as neostigmine and gentamicin, which are highly ionised, are poorly absorbed.
Summarize the impact of gestational age, postnatal age, and disease state on drug absorption, distribution, metabolism, and elimination. Food, other drugs, and digestive disorders can affect drug absorption and bioavailability. In most cases, the absorption of drugs from the gastrointestinal tract is reduced or delayed by food. 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. Factors affecting drug absorption and distribution sciencedirect. Factors affecting drug absorption authorstream presentation. The use of mathematical principles and methods to explain the plasma concentration with time changes in a discipline. Anatomical, physiological and experimental factors. Patient related factors affecting on drug absorption, drug absorption, absorption, factors affecting, patient related factors. Describe two types of drug interaction and explain how. Factors affecting absorption of a drug from its dosage form. Invitro dissolution testing or drug release testing may be used for seeking waiver of required product to conduct invivo bioavailability or bioequivalence studies. For many drugs, the gastrointestinal absorption rate, but not the extent of absorption, is reduced by the presence of food in the gut.
Pdf factors affecting intraocular bioavailability of drugs. 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. Factors affecting drug absorption linkedin slideshare. 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. The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug concentration gradient.
However, some drugs are unaffected by food, while the absorption of a small number of drugs is increased. The pharmacokinetic properties of a drug comprise the relationship between its absorption, distribution and inactivation. Influence of food and diet on gastrointestinal drug. This article throws light upon the eight main physiological factors that affect the rate of drug absorption. 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. Nov 01, 2002 after completing this article, readers should be able to. Salt forms of these drugs cannot be prepared because the free base readily precipitates out due to the weak basicity. Pharmacological and pathophysiological role of histamine and releasers of histamine and betahistine drug what is epg pathshala, eadhyayan, ugc moocs and epathya pharmacokinetic. 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. Physiochemical factors affecting drug absorption free download as powerpoint presentation. This chapter answers parts from section bii of the 2017 cicm primary syllabus, which expects the exam candidate to describe absorption. Binding to plasma proteins will increase the rate of passive absorption by maintaining the concentration gradient of free drug.
The distribution and rate of equilibration across the placenta are determined by placental blood flow and the free drug. 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. Absorption, factors affecting absorption includes route of administration, bioavailability and bioequivalence. The following factors can affect the blood concentrations of a drug. Neonatal pharmacology and pharmacokinetics american. Physiologically, a drugs absorption is enhanced if there is a large surface area available for absorption e. Dapsone, itraconazole, and ketoconazole may also be less well absorbed in the presence of. Lipid water solubility coefficient is the ratio of dissolution of drug in lipid as compared to water. For many drugs, the gastrointestinal absorption rate, but not the extent of absorption, is reduced by the presence of food in the.
Moreover, the drug s pharmacokinetic profile can be easily and significantly changed by adjusting factors that affect absorption. Anatomical, physiological and experimental factors affecting. Factors influencing product bioavailability include drug sol ubility, permeability, and the. The rectum is an interesting area for drug absorption because it is not buffered and has a neutral ph. There are four factors that will influence the pharmacokinetic drugs test. Georgetown university, has developed a free database summarizing. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Write in detail about the factors that are related to the physiological conditions and formulation of dosage form. A mechanistic approach to understanding the factors affecting drug absorption. For example, highfiber foods and calcium supplements may bind with a drug and prevent it from being absorbed. Factors that increase gastric emptying will usually increase the rate of absorption of a drug. 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.
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. Laxatives and diarrhea, which speed up the passage of substances through the digestive tract, may reduce drug absorption. Scribd is the worlds largest social reading and publishing site. Write in brief about factors affecting drug absorption. Pharmaceutical factors a chemical factors b physicochemical properties of drug substances 1. When the salt of a weak acid dissolves in the stomach, it generates a diffusion layer of relatively high ph which,in turn, promotes. Exogenous factors influencing insulin absorption are summarized in table 2. Factors which influence gastrointestinal drug absorption deranged. 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 drug absorption free download as powerpoint presentation. 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. Intestinal transporters play an important role in drug absorption. Drug absorption drugs merck manuals consumer version. 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 influencing product bioavailability include drug solubility. Factors affecting surface drug absorption many factors affect how the application of a particular drug will be absorbed by the skin surface. Factors affecting drug absorption and distribution request pdf. Anatomical, physiological and experimental factors affecting the bioavailability of sc administered large biotherapeutics. Other factors that also impact drug absorption include the following. Oral administration of a drug with food generally reduces its absorption. Many drugs will bind strongly to proteins in the blood or to food substances in the gut. Neonatal pharmacology and pharmacokinetics american academy. List two physiologic factors that can alter each of the processes of absorption, distribution, and excretion. Factors affecting pharmacokinetics of drugs medicilon inc. Absorption is a primary focus in drug development and medicinal chemistry, since the drug must be absorbed before any medicinal effects can take place.
Pdf overview of factors affecting oral 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. The systemic absorption of a drug is dependent on 1 the physicochemical. Factors affecting drug absorption small intestine stomach. There are many factors that can affect the absorption process of orally administered drugs. The oral absorption of any chemical entity reflects a complex spectrum of events. Observed effects of food on drug absorption are the net result of various factors.
In rectal absorption both low and high molecule weight compounds in a constant ratio of absorption. Factors influencing product bioavailability include drug solubility, permeability, and the rate of in vivo dissolution. Trafficking the drug effectively through the lymphatic may alleviate the load on uptake transporters and enhance overall bioavailability of injected therapeutic proteins. Clinical pharmacokinetics is the application of pharmacokinetic principles to the safe and effective therapeutic management of drugs in. The factors affecting absorption of drugs are related both to the drugs and to the body. Compare the roles of passive diffusion and carriermediated transport in drug 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. Drug absorption, drug distribution, drug dissolution, drug solubility introduction. Factors affecting drug absorption flashcards quizlet. 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. Greater the lipid water solubility coefficient, more is the lipid solubility of the drug and greater is the absorption. 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. Necrosis, type of necrosis, oxygen derived free radicle, antioxidant histamine.
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