Pharmacology 2nd meeting

Pharmacokinetics
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Terms in this set (55)
Pharmacokinetics
examines the way in which the body handles drugs
Oral route
is the most used and convenient method of administration of drugs. Drugs passes into the intestines via the stomach.
Phospholipids
are simply lipids (fats) that contain an atom of phosphate
Hydrophobic
tends to repel or not to absorb water example oil and fats.
Hydrophilic
ability to mix well, dissolve, or to be attracted to water
Passage through channels or pores
are extremely small (approximately 4 angstroms or less), and only the smallest of compounds and those that are specific for certain molecules. (e.g., potassium or sodium)
Passage with the aid of a transport system
are selective they move drugs from one side of the cell membrane and some transport system requires the expenditure of energy.
P-Glycoprotein
or multidrug transporter protein. It is a transmembrane protein that transports a wide variety of drugs out of cells.
Direct penetration of the membrane itself (the most common)
most drug movement directly penetrate membranes, a drug must be lipid soluble (lipophilic).
Polar molecules
have an equal number of protons (which bear a single positive charge) and electrons (which bear a single negative charge). They are considered as charge molecules
Ionsare defined as molecules that have a net electrical charge (either positive or negative). Except for very small molecules, they are unable to cross membranesProcess of absorptionthe movement of a drug from its site of administration into the blood.The rate of absorptiondetermines how soon effects will begin.The amount of absorptiondetermine how intense effects will be.Passive diffusionrefers to the movement of substances from an area of higher concentration to an area of lower concentrationFacilitated diffusionrefers to the movement of substances from an area of higher to an area of lower concentration using a carrier protein in the cell membraneActive transport- refers to the movement of a substance across a cell membrane going from an area of lower concentration to an area of higher concentration. this type of transport, proteins within the cell membrane act as "pumps," using cellular energy (ATP) to move the substance.Endocytosistransportation process in which the cell membrane engulfs material. when a portion of the cell membrane folds in on itself, encircling extracellular fluid and various molecules or microorganisms. The resulting vesicle breaks off and is transported within the cell.Acidstend to ionize in basic (alkaline) media.the proximal duodenumAcidic part of the stomach (weak acid) nonpolar and easily absorbed. Located in_____Basestend to ionize in acidic mediadistal ileumbases are best absorbed in the ___Blood FlowThe greater the concentration gradient, the more rapid absorption will be. Example of disease with low blood flow is any form of shock.Surface areaa major determinant of the rate of absorption. The larger the surface area, the faster absorption will be. The larger the surface area, the faster absorption will be. For this reason, orally administered drugs are usually absorbed from the small intestine rather than from the stomach.Lipid Solubilityhighly lipid-soluble drugs are absorbed more rapidly than drugs whose lipid solubility is low. Because lipid soluble drugs can readily cross the membranes that separate them from the blood, whereas drugs of low lipid solubility cannot.P-Glycoproteincommon seen to patients that are multidrug resistant.BioavailabilityA term that is used to describe the amount (sometimes referred to as the fraction) of the administered dose that reaches the systematic circulation which is available to have an effect.DistributionA drug enters the systemic circulation, it is distributed to the body's tissues.Abscessesis a pus-filled pocket of infection that has no internal blood vessels, it lacks a blood supply and antibiotic cannot reach the bacteria within. The abscess must first be surgically drainedTumors (solid)have a limited blood supply. The major reason why solid tumors are resistant to drug therapy; blood flow to the outer regions of tumor is relatively high, blood flow becomes progressively lower toward the core.Blood flow to tissuesthe rate at which drugs are carried by the blood to the tissues and organs of the bodyability of a drug to exit the vascular systemthe ability to leave the blood at capillary beds because most drugs do not produce their effects within the blood.typical capillary BedIn most capillary beds, "large" gaps exist between the cells that compose the capillary wall. Drugs and other molecules can pass freely into and out of the bloodstream through these gaps. As illustrated, lipid-soluble compounds can also pass directly through the cells of the capillary wall.Blood Brain Barrierunique anatomy of capillaries in the CNS because if its tight junctions that prevent drug passage.placental drug transferThe membranes of the placenta separate the maternal circulation from the fetal circulation BUT the membranes of the placenta do NOT constitute an absolute barrier to the passage of drugs.protein bindingMany drugs bind reversibly to plasma albumin. While bound to albumin, drug molecules cannot leave the vascular system.Volume distributionis used to reflect the amount of drug left in the blood stream (Plasma) after all the drug has been absorbed and distributed.MetabolismThis is the process by which the body modifies or breaks down chemicals (including drugs) allowing eventual elimination from the body.liverMetabolism of drugs mainly occurs in the ____first-pass metabolism or first-pass effectremoval or modification of a drug, before it is available to have an effect. only a fraction of drug may eventually reach the tissues to have a therapeutic effectEnzyme-inducing or -inhibiting drugs-Some drugs increase the activity of enzymes in the liver that break down drugs - so a larger dose of affected drug is needed for a therapeutic effect. (Enzyme inducers, e.g. carbamazepine) -Some drugs may inhibit or reduce enzyme production which reduces the rate at which another drug is inactivated - so a smaller dose of affected drug is needed for a therapeutic effect.Hepatic microsomal enzyme-Most drug metabolism takes place in the liver. (enzyme inhibitors, e.g. erythromycin) -also known as P450 system.P450 refers to cytochrome P450play an important role in the adverse drug reactions patients may have when taking several drugs at the same time or when there are drug-food interactions. Because there are individual genetic differences in the enzyme pathways, different patients may respond differently to the same medicationsEntero-hepatic recyclingThe liver can transfer substances, including drugs, either unchanged or as conjugated drug (metabolite), to the gallbladder in bile.Glomerular filtrationacts like a sieve, allowing small drugs and those not bound to plasma proteins to filter from the blood to the proximal tubuleActive secretion(by transport carriers) into the proximal tubuleTherapeutic window or indexDenotes the maximum and minimum levels between which a drug is effective; above the maximum level the drug becomes toxic, and below the minimum, the drug is ineffective (subtherapeutic).Half-life (t1/2)The duration of action of a drug. This is the period of time required for the concentration or amount of drug in the body to be reduced by one-half of its original value.Dosingare based on half-life data giving regimens that produce stable blood levels - keeping them below toxic, but above minimum effective levels.Pharmacodynamicsis the study of the way drugs affect the body. Drug response can cause a primary or secondary physiologic effect or both. The primary effect is desirable, and the secondary effect may be desirable or undesirable.Dose responseis the relationship between the minimal versus the maximal amount of drug dose needed to produce the desired drug response.Onset of actionis the time it takes to reach the minimum effective concentration (MEC) after a drug is administered.Peak actionoccurs when the drug reaches its highest blood or plasma concentrationDuration of actionis the length of time the drug has a pharmacologic effect.time-response curveevaluates three parameters of drug action: the onset of drug action, peak action, and duration of action.