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MODULE 2-BIOPHARM GLOSSARY OF USEFUL TERMS:
A’s
Absolute Bioavailability -is the extent or fraction of drugs absorbed upon extravascular administration in comparison to the dose size administered. Absorption -of drugs is the process of uptake of compound from the site of administration into the systemic circulation. A prerequisite for absorption is that the drug be in aqueous solution. The only relatively rare exception is absorption by pinocytosis. Accumulation -is the increase of drug concentration in blood and tissue upon multiple dosing until steady state is reached. Area Under the Curve is the integral of drug blood level over time from zero to infinity and is a measure of the quantity of drug absorbed and in the body. Area Under First Statistical Moment Curve- the area under the curve observed for the product of time and concentration versus time.
B’s
Biliary Recycling [Enterohepatic Recirculation]- is the phenomenon that drugs emptied via bile into small intestine can be reabsorbed from the intestinal lumen into systemic circulation. Bioavailability -is defined as both the relative amount of drug from an administered dosage from which enters the systemic circulation and the rate at which the drug appears in the blood stream. Bioequivalence - of drug product is achieved if its extent and rate of absorption are not statistically and significantly different from those of the standard when administered at the same molar dose. Bioequivalent Requirement- is a requirement imposed by the Food and Drug Administration for in vitro and/ or in vivo testing of specified drug products which must be satisfied as a condition of marketing. Biological half-Life [see Elimination half-life] Biopharmaceutics -deals with the physical and chemical properties of the drug substance, the dosage form and the body, and the biological effectiveness of a drug product upon administration. Or -It is about the drug delivery system , which is the drug availability to the human or animal body from a given dosage form. BioPhase -is the site of action of drugs in the body. It is the drug/receptor interaction on molecular level or the influence of biopolymers by the presence of the drugs. The BioPhase maybe the surface of the cells, or within the cell, i.e.., one of the organelles. Blood Flow Rate -is the speed of blood perfusion in an organ .This is expressed in ml/100 gram of organ weight/min. Blood flow rate may differ several fold between rest, or immobilization and exercise.
Blood, Plasma or Serum Levels- demonstrate the concentration of dosage form in blood, plasma, or serum upon administration by various routes. Blood, plasma or serum levels are plots of drug concentration versus time on numeric or semi-log graph paper .This is obtained from blood sample by venipuncture in certain time intervals after administration of drug product and chemical or microbiological analysis of the drug in the biological fluid.
C’s
Central Compartment -is the sum of all body regions [organs and tissues] in which the drug concentration is in instantaneous equilibrium with that in blood or plasma. The blood or plasma is part of the central compartment. Chronopharmacokinetic -is the study of pharmacokinetic drug parameters as affected by circadian rhythm or diurnal variation. Circadian Rhythm -is the biological clock controlling rhythms of processes during a twenty- four-hour cycle which is based on endogenous factors. Clearance- is the hypothetical volume of distribution in ml of the unmetabolized drug which is cleared per unit of time [ml/min. or ml/hr.] by any pathway of drug removal [renal, hepatic, and other pathways of elimination] Clinical Pharmacokinetics -is the application of Pharmacokinetic Principles in the safe and effective treatment of individual patients, and in the optimization of drug therapy. A Compartment- in pharmacokinetics is an entity which can be described by a definite volume and a concentration of drug contained in that volume .In Pharmacokinetics, experimental data are explained by fitting them to compartment models. Concentration gradient -is the difference in the concentration in two phases usually separated by a membrane. Creatinine Clearance -is the ratio of creatinine excreted in urine to the concentration of creatinine In plasma. The creatinine clearance decreases with renal impairment and with age
D’s
Depot phase- is that portion of a prolonged released dosage form which liberates the drug from the dosage form at a slower rate than its unrestricted absorption rate. Diffusion layer -is the viscous layer of concentrated drug solution around a dissolving particle. Disposition -is the loss of drug from the central compartment due to transfer [distribution] into other compartments and/or elimination and metabolism.
Enzyme Induction is the increase in enzyme content or rate of enzymatic process resulting in faster metabolism of a compound. If a drug stimulates its own metabolism, it is called auto-induction, and, if it is caused by other compounds. Enzyme inhibition i s the decrease in rate of metabolism of a compound usually by competition for an enzyme system. Excretion of drugs is the final elimination from the body’s systemic circulation via the kidney into urine, via bile and saliva into intestine and into feces, via sweat, via skin and via milk. Extravascular administration refers to all routes of administration except those where the drug is directly introduced into the bloodstream. Extravascular routes are I.M, S.C,P.O, Oral, Rectal, I.P. ,Topical. Etc. Enterohepatic recirculation [Biliary recycling]- is the phenomenon in which the drugs emptied via bile into small intestine can be reabsorbed from the intestinal lumen into systemic circulation. Enzyme induction -is the increase in enzyme content or rate of enzymatic processes resulting in faster metabolism of a compound. If a drug stimulates its own metabolism, it is called Auto-Induction ; and if it caused by other compounds, it is called Foreign-Induction. Enzyme-Inhibition- is the decrease in rate of metabolism of a compound usually by competition for an enzyme system. Excretion of drugs is the final elimination from the body’s systemic circulation via the kidney into the urine, via bile and saliva into intestine and into feces, via sweat, via skin and via breastmilk. Extravascular Administratio n refers to all routes of administration except those where the drug is directly introduced into the bloodstream. Extravascular routes are I.M, S.C, P.O, Oral, Rectal, I.P, Topical, etc. F’S First-pass Effect describes the phenomenon whereby drugs maybe metabolized following absorption, before reaching systemic circulation. Hepatic first pass effect may occur following P.O and deep Rectal administration. It may be avoided by using sublingual and buccal routes. Pulmonary first pass effect cannot be avoided by intravenous, buccal, or sublingual routes. Flip-Flop model is the phenomenon observed if the rate of absorption is slower than the rate of elimination, or if one of the distribution rates is slower than the rate of elimination. G’s The Gastrointestinal Tract [GIT] is a part of the alimentary canal comprising stomach, small and large intestine. A Generic Product is a drug product marketed under the non-proprietary or common name of the drug.
H’s Hepatic clearance is the hypothetical volume of distribution in ml of the unmetabolized drug which is cleared in one minute via the liver. Homeostasis i s the maintenance of the steady state which characterizes the internal environment of the healthy organism. An important function of homeostasis is the regulation of the fluid medium and volume of the cell. I’s Initial phase is that portion of a prolonged release dosage form which is immediately available for absorption. Intravascular administration refers to all routes of administration where the drug is directly introduced into the bloodstream, [i.e. I.V, Intracardiac, intraarterial: Bioavailability=100 percent f= L’s The LADMER System deals with the complex dynamic processes of Liberation-of active ingredient Absorption-into systemic circulation Distribution-by the body fluids Metabolism=in the liver Excretion-of drug from the body Response -to be achieved. Lag time is the period of time which elapses between the time of administration and the time of measurable drug concentration is found in blood .lag time are often found upon P.O administration due to slow disintegration and dissolution of tablets or capsules. Lean body weight is a patient’s body weight minus the fat mass. Drugs of low lipid solubility should be dosed in obese patients according to Lean body weight. Loading dose, Priming dose or Initial dose is the dose size used in initiating therapy so as to yield therapeutic concentration which will result in clinical effectiveness. Local effect- is obtained when the drug product is administered at the site where the pharmacological response is desired and when the drug released from the product acts by adsorption to the skin or mucosa or penetrates into the skin or mucosa, but does not enter the systemic blood circulation or lymphatic stream. M’s Maintenance Dose is the dose size required to maintain the clinical effectiveness, or therapeutic concentration according to the dosage regimen. Mean transit time or Residence Time is the time when t63.2 percent of intravenous dose has been eliminated from the pharmacokinetic system.
Relative Bioavailability is the extent of drug absorbed upon extravascular administration in composition to the dose size of a standard administered by the same route. Renal Clearance is the hypothetical plasma volume in ml [volume of distribution] of the unmetabolized rug which is cleared in one minute via the kidney. S’s Single dose administration occurs when next dose of the same drug is administered only after the drug of the previous dose is completely eliminated from the body. Sorption Promoters or Permeation Enhancers are defined as substances that have no pharmacological properties of their own in the amount used, but which can improve the penetration of drugs into the skin or their permeation through skin or mucosa by reducing the barrier resistance. Steady State is a level of drug accumulation in blood and tissue upon multiple dosing when input and output are ay equilibrium. The steady state drug concentration fluctuate [oscillate] between a maximum and minimum steady state concentration without each dosing interval. Structural Non-Specific Drugs are -Drugs with no functional group [therefore, pharmacological action is not dependent on the chemical structure] -Do not react easily -Acts by physico-chemical properties -highly lipophilic -Examples: ether, nitrous oxide, halothane, phenol, ethyl alcohol, octyl alcohol, acetone. Structural Specific Drugs are -have functional group [Therefore pharmacological action is dependent on the chemical structure] -Acts easily -Examples: antibiotics, sulfonamides, Glycosides, Alkaloids, etc. Sustained Release is the property of prolonged released dosage forms where the liberation [drug release] rate constant is smaller than the unrestricted absorption rate constant. Systemic effect is obtained when the drug released from drug product enters the blood and/ or lymphatic streams and is distributed within the body-or at least in several organs-regardless of site and route of administration. T Total Clearance describes the clearance of the hypothetical plasma volume in ml [volume of distribution] of a drug per unit time due to excretion via kidney, liver, lung, skin, etc. and metabolism. U’s A unit membrane is a physical barrier to transport in the body. It is a lipoidal in nature and consist of a double row of phospholipids sandwiched between one layer of proteins.
Urinary recycling is the phenomenon that occurs when drugs filtered through the glomeruli are reabsorbed from the tubuli into systemic circulation. V’s Vehicle is the carrier of the drug in the drug product. It is composed of all necessary vehicle substances. Vehicle substances are additives which are necessary in formulating a dosage form from the drug. The vehicle substances should be chemically inert and should not have any pharmacological effect in the dose used. Vehicle substance are used to produce from a relatively small amount of drug, dosage form of the desired strength, volume, or consistency suitable for administration. Volume of distribution is not a “real’ volume but an artifact- a hypothetical volume of body fluid that would be required to dissolve the total amount of drug at the same concentration as that found in the blood. It is proportionally constant relating the amount of drug in the body to the measured concentration in biological fluid [blood, plasma, or serum.
