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40 Cards in this Set

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Therapeutic effect of the drug
p47 depends on if and how much reaches its target cells
Pharmacokinetics
"medicine" and "movement or motion"
study of drug movement in the body. Helps nurses better understand and predict the actions and side effects of medications in their patients
Study of pharmacology helps a nurse . . .
p47 Better understand and predict the actions and side effects of medications in their patients. For most medications, the greatest barrier is crossing the many membranes that separate the drug from its target cells.
Barriers to medication . ..
dig. enzymes and stomach acids break it down or make it less active, phagocytes make attempt to remove it, immune response may be triggered, certain organs try to excrete
The many processes of pharmacokinetics are grouped into 4 categories:
absorption, distribution, metabolism, excretion
Pharmacokinetics variables depend on the ability of a drug:
to cross plasma membranes
Drugs use two processes to cross body membranes
1. Diffusion/passive transport - Movement of a chemical fr. an area of higher conc. to area of lower conc. 2. Active transport - movement of a chemical against a conc. or electrochemical gradient. (large or ionized molecules or H2O soluble)
Plasma Membrane
Consists of lipid bilayer, lipophilic, and is relatively impermeable to large molecules, ions, and polar molecules. For ex: Drug molecules that are small, nonionized, and lipid soluble will usually pass through plasma membranes by simple diffusion and more easily reach their target cells.
Some drugs do NOT need to enter plasma membrane of the target cell
Once bound to the receptor on plasma mem, some drugs activate a second messenger w/in the cell that produce the physiological change
Absorption
p48 Process involving the movement of a substance fr. its site of admin, across body mem, to circulating fluids.
Most Drugs must be absorbed to
Produce its effect.
The degree of ____of a drug also affects its absorption
p49 ionization - high pH like the stomach allows the ionization of a drug, like aspirin. In the acid environment of the stomach, aspirin is in its nonionized form and is easily absorbed and distributed by the bloodstream. It becomes ionized when it enters sm. int because of alkaline environment.
Unlike acidic drugs,, medications that are weakly basic are in their nonionized form in an . .. .
p49 alkaline environment; basic drugs are absorbed and distributed better in alkaline environments of the sm. int. Acids are absorbed in acids, bases in bases. Non-ionized leads to absorption.
What foods/ minerals slow drug absorption?
High fat meals slow stomach motility. Tetracyclines slow w/ calcium, Fe, magnesium. Dietary supplements also slow it. Herbal weight loss pill ingredients create a laxative effect and decrease intestinal transit time and reduce drug absorption. Nurse must advise on these interactions.
What is the simplest factor determining distribution of a drug in the body?
p49 blood flow to body tissues. Heart, liver, kidneys, and brain - high flow. Skin, bone, and adipose - low.
Which is more easily distributed in the body, lipid soluble drugs or water?
p49 Lipid Soluble! These are not limited by the barriers that normally stop water-soluble drugs; thus, they are more completely distributed to body tissues.
Which tissues accumulate and store drugs after absorption?
bone marrow, teeth, eyes, and adipose tissue have a high affinity for some medications. It will slowly release it over months into the circulation.
Drug -protein complexes
p49 Not all drug molecules in the plasm will reach their target cells, because many drugs bind reversibly to plasma proteins, particularly albumin. these are too LARGE to cross capillary membranes. ie Coumadin - anticoagulant
Drug-drug and drug-food
p50 interactions may occur when one agent displaces another fr. plasma proteins. The displaced medication can immediately reach high levels producing an adverse effect. ie Coumadin and aspirin - chance of hemorrhage!
Blood brain barrier and fetal-placental barrier
p50 Brain and placenta have special anatomical barriers that inhibit many chemicals and medications from entering. Sedatives, anitanxiety agents, and anticonvulsants easily cross, but antitumor medications do not!
Metabolism (aka biotransformation)
p50 The process of chemically converting a drug to a form that is usually more easily removed fr the body. Site - liver (primary), kidney, and cells of intestinal tract
Medications undergo many types of biochemical reactions as they pass through the liver including
p50 hydrolysis, oxidation, reduction and during metabolism the addition of side chains are added - CONJUGATES. These make drugs more water soluble and more easily excreted by the liver.
Most metabolism in the liver is accomplished by the . . .
p50 Hepatic microsomal enzyme system. This enzyme complex is sometimes called the P-450 system, named after cytochrome p-450 (ETC), wh. is a key component of the system. Inactivates drugs and accelerate their excretion. Sometimes, it can make it more active than original.
Example of metabolism increasing activity of a drug
Narcotic analgesic codeine undergoes biotransformation to morphine - greater ability to relieve pain! PRODRUGS - no pharmacological activity unless they are first metabolized by body.
A few drugs have the ability to increase metabolic activity in the liver, a process called . ..
Enzyme induction. When metabolism is occurring at a faster rate, more of the drug is needed to achieve the optimum therapeutic effect.
Decrease in hepatic metabolic activity . . .
More sensitive to drugs therapy, ie infants, elderly, those with severe liver damage (cirrhosis)
The rate at wh. medication are excreted determines . .. .
p51 . . their concentration in the bloodstream and tissues. This is important because the concentration of drugs in the bloodstream determines their duration of action. Excretion - primarily kidneys - roughly 180 L of blood is filtered by kidneys ea day.
Which products in kidneys is excreted and which are reabsorbed?
Which are not filtered at the glomerulus?
p51 ionized and water-soluble drugs generally remain in the filtrate for excretion. Nonionized and lipid soluble drugs return to circulation. Proteins, blood cells, conjugates, and drug-protein complexes are not filtered because of their large size.
Certain drugs may be excreted more quickly if the __ of the filtrate changes.
p51 pH. Weak acids such as aspirin are excreted faster when the filtrate is slightly alkaline, because aspirin is ionized in an alkaline environment, and the drug will remain in the filtrate and be excreted in the urine. Weakly basic drugs like Valium are excreted faster in a slightly acid filtrate.
Drugs that can easily be changed into a gaseous form are especially suited for excretion by the ______.
p51 Respiratory system. The rate of respiratory excretion is dependent on factors that affect gas exchange, including diffusion, gas solubility, and pulmonary blood flow. The faster the breathing rate, the greater the excretion of volatile anesthetics after a surgery. also water soluble agents such as alcohol. Lungs excrete most drugs in their original unmetabolized forms.
The "funny taste" clients sometimes have from IV drugs is an example of ---------.
p52 Glandular activity (elimination mechanism) of saliva. Also in breast milk and sweat. Water soluble drugs may be excreted through these glands.
Biliary excretion
p52 Some drugs are secreted in the bile. Enter duodenum and leave the body in the FECTES. MOST bile is circulated back to the liver by enterohepatic recirculation. May be recirculated a number of times. Extremely influentila in prolonging activities of cardiac glycosides,etc. Eventually, these drugs are metabolized by liver and excreted. Continues for weeks.
The therapeutic response of most drugs is directly related to their .....
p52 . . .level in the plasma. Although the concentration of the medication at its t.t.is more predictive of drug action, this quantity is impossible to measure in most cases. Blood sample for conc of drug in blood.
Minimum effective concentration
toxic concentration
Therapeutic Range
p53. The amount of drug required to produce a therapeutic effect. The level of drug that will result in serious adverse effects. The plasma drug concentration between the minimum effective concentration and toxic concentration is called the therapeutic range of the drugs.
For ea. drug administered, the nurse's goal is to keep its plasma concentration in the _________.
Maintenance Dose
p53 Therapeutic Range, doses of medication given to keeps medication in therapeutic range in the plasma.
The most common description of a drug's duration of action is its _____.
p53 plasma half life (t 1/2), defined as the length of time required for the plasma conc. of a medication to decrease by half after admin.
Theoretically it takes approximately ------ to reach an equilibrium (drug coming in to maintain therapeutic level w/ amount being excreted) of the drug to be maintained at a therapeutic level.
p53 4 half lives. If the medication is given as a continuous infusion, the plateau can be reached quickly and be maintained w/ little or no fluctuation in drug plasma levels.
The plateau may be reached faster by admin. of loading doses followed by regular maintenance. What is a loading dose?
p53,54 is a higher amount of drug, often given only once or twice, that is administered to "prime"the bloodstream w/ a level sufficient to quickly induce a therapeutic response.
Enterohepatic Recirculation
Most bile is circulated back to the liver (different from biliary excretion - leaves through feces). Recirculated drugs (in the bile) are ultimately metabolized by the liver and excreted by the kidneys.
The nurse understands that which of the following terms refers to the removal of larger drug metabolites from the bloodstream to the urine?
Secretion