Section 2: Mechanisms of Drug Action Flashcards
True or False:
Drugs generally exert several effects rather than a single one
True (Pg. 282)
Why is it important to obtain a patient medical history and being able to recognize and understand the reasons why certain drugs are prescribed?
May help establish a field diagnosis. Thus, being able to use the right drug to manage the illness, disease, or condition. (Pg. 282 NOTE)
True or False:
Drugs do not confer any new functions on a tissue or organ; they only modify existing functions.
True (Pg. 283)
Pharmacology Terminology:
A drug that interacts with a receptor and initiates the expected response
Agonist (Pg. 283)
Pharmacology Terminology:
A drug that attaches to a receptor but does not stimulate a response.
Or
Designed to inhibit or counteract the effects of other drugs or undesired effects caused by normal or hyperactive physiological mechanisms
Antagonist (Pg. 283)
Pharmacology Terminology:
The opposition of effects between two or more medications that occurs when the combined (conjoint) effect of two drugs is less than the sum of the drugs acting separately.
Antagonism (Pg. 283 Box 13-4)
Pharmacology Terminology:
Medical or physiological factors that make it harmful to administer a medication that would otherwise have therapeutic value
Contraindications (Pg. 283 Box 13-4)
Pharmacology Terminology:
The tendency for repeated doses of a drug to accumulate in the blood and organs, causing increased and sometimes toxic effects; it occurs when several doses are administered or when absorption occurs more quickly than removal by excretion or metabolism
Cumulative action (Pg. 283 Box 13-4)
Pharmacology Terminology:
A substance that decreases a body function or activity
Depressant (Pg. 283 Box 13-4)
Pharmacology Terminology:
A systemic reaction to a drug resulting from previous sensitizing exposure and the development of an immunological mechanism
Drug allergy (Pg. 283 Box 13-4)
Pharmacology Terminology:
A state in which withdrawal of a drug produces intense physical or emotional disturbance, previously known as habituation
Drug dependence (Pg. 283 Box 13-4)
Pharmacology Terminology:
Beneficial or detrimental modification of the effects of one drug by the prior or concurrent administration of another drug that increases or decreases the pharmacological or physiological action of one or both drugs
Drug interaction (Pg. 283 Box 13-4)
Pharmacology Terminology:
Abnormal or peculiar responses to a drug (accounting for 25% to 30% of all drug reactions) thought to result from genetic enzymatic deficiencies or other unique physiological variables and leading to abnormal mechanisms of drug metabolism or altered physiological effects of the drug.
Idiosyncrasy (Pg. 283 Box 13-4)
Pharmacology Terminology:
The enhancement of effect caused by the concurrent administration of two drugs in which one drug increases the effect of the other drug.
Potentiation (Pg. 283 Box 13-4)
Pharmacology Terminology:
Undesirable and often unavoidable effect of using therapeutic doses of a drug; action or effect other than those for which the drug was originally given.
Side effect (Pg. 283 Box 13-4)
Pharmacology Terminology:
A drug that enhances or increases body function or activity
Stimulant (Pg. 283 Box 13-4)
Pharmacology Terminology:
The combined effect of two drugs such that the total effect equals the sum of the individual effects of each agent (1+1=2)
Summation (Pg. 283 Box 13-4)
Pharmacology Terminology:
The combined action of two drugs such that the total effect exceeds the sum of the individual effects of each agent. (1+1=3 or more)
Synergism (Pg. 283 Box 13-4)
Pharmacology Terminology:
The desired, intended action of a drug
Therapeutic action (Pg. 283 Box 13-4)
Pharmacology Terminology:
Decreased physiological response to the repeated administration of a drug or chemically related substance, possibly necessitating an increase in dosage to maintain a therapeutic effect (tachyphylaxis)
Tolerance (Pg. 283 Box 13-4)
Pharmacology Terminology:
A side effect that proved harmful to the patient
Untoward effect (Pg. 283 Box 13-4)
Pharmaceutical Phase:
All drugs must be in ________ to cross the cell membranes to achieve absorption. The term ________ refers to the rate at which a solid drug goes into solution after ingestion. The faster the rate of ________, the more quickly the drug is absorbed.
Solution, Dissolution, Dissolution (Pg. 283)
The study of how the body handles a drug over a period of time.
Pharmacokinetics (Pg. 283)
The process of absorption, distribution, biotransformation, and excretion. These factors affect a patients response to drug therapy
Pharmacokinetic Phase (Pg. 283)
The movement of drug molecules from the entry site to the general circulation
Absorption (Pg. 283)
The rate and extent of a drug depend on the ability of the drug to cross the cell membrane.
Which type of process does the drug cross the cell membrane through?
Passive diffusion and active transport (Pg. 283 - also described in chapter 11)
The Pharmacokinetic Phase includes which processes?
Drug Absorption
Drug Distribution
Biotransformation
Excretion
(Pg. 283-289)
True or False:
Most drugs enter the cell by carrier-mediated mechanism. Yet some drugs enter by passive diffusion to assist them across the membrane.
False (Pg. 283)
Most drugs enter the cell by passive diffusion.
The rate and extent of absorption depend on these 6 factors:
- The nature of the absorbing surface (cell membrane) the drug must traverse
- Blood flow to the site of administration
- The solubility of the drug
- The pH of the drug environment
- The drug concentration
- The form of the drug dosage
(Pg. 283-284)
True or False:
Drugs that are prepared in oily solutions are absorbed more slowly than drugs dissolved in water or in isotonic sodium chloride
True (Pg. 284)
Ionized (electrically charged) or Nonionized (uncharged)?
Lipid (fat) soluble and readily diffuses across the cell membrane?
Nonionized (Pg. 284)
Ionized (electrically charged) or Nonionized (uncharged)?
Lipid insoluble and generally does not cross the cell membrane?
Ionized (Pg. 284)
An acidic Drug such as aspirin (Nonionized) does not dissociate well in an acidic environment such as the stomach.
Aspirin does or does not absorb easily in the stomach?
Does (Pg. 284) vice versa
Loading dose Vs. Maintenance dose
Loading dose (Large dose)- A large quantity of drug that temporarily exceeds the capacity of the body to excrete the drug.
Maintenance dose (Smaller dose)- The amount of a drug required to keep a desired steady state of drug concentration in tissues.
(Pg. 284)
4 main routes of drug administration
Enteral (gastrointestinal tract)
Parenteral (other than gastrointestinal tract)
Pulmonary (inhalation or ET tube)
Topical (skin and mucous membranes)
(Pg. 284)
Enteral (gastrointestinal tract) route, allows for which four types of absorption?
Oral absorption
Gastric absorption
Absorption from the small intestine
Rectal absorption
(Pg. 284-285)
Oral Absorption:
Drugs that are absorbed in the upper gastrointestinal tract enter the 1.____. They initially bypass gastrointestinal fluids and the liver. Drugs absorbed in the stomach and intestines pass through the 2.___. of the liver. They are subject to first-pass metabolism.
A. Systemic Circulation
B. Portal Vein System
- A
- B
(Pg. 284-285)
The initial biotransformation of a drug during passage through the liver from the portal vein that occurs before the drug reaches the general circulation.
First-Pass Metabolism (Pg. 285)
Gastric Absorption
Not considered an important site of drug absorption. The length of time a medication remains in the stomach varies, depending on the pH of the environment and gastric mobility (Pg. 285)
Most drug absorption occurs in which part of the small intestine?
Upper part (Pg. 285)
The pH of intestinal fluid is (alkaline or acidotic?) which increases the rate of absorption of basic drugs.
Alkaline (Pg. 285)
Which drug routes are considered to have a “slow” rate of absorption?
Enteral, Subcutaneous (Pg. 284 Table 13-2)
Which drug routes are considered to have a “Rapid” rate of absorption?
Sublingual, Endotracheal, Pulmonary (Pg. 284 Table 13-2)
Which drug routes are considered to have a “Moderate” rate of absorption?
Intramuscular, Topical (Pg. 284 Table 13-2)
Which drug routes are considered to have a “Immediate” rate of absorption?
Intravenous, Intraosseous (Pg. 284 Table 13-2)
What are the 6 commonly used parenteral (any route other than gastrointestinal route) routes for administering medications?
Subcutaneous Intramuscular Intravenous Intradermal Intraosseous Endotracheal
(Pg. 285-286)
Subcutaneous injection is only used for small volumes of drugs. How many mL may be injected?
0.5 mL or less (Pg. 285)
More info: slow rate of absorption
Why does the intramuscular route absorb more rapidly than the subcutaneous route?
IM into the skeletal muscle has greater tissue blood flow (Pg. 285)
Which route bypasses the absorption process and produces an almost immediate pharmacological effect?
Intravenous route (Pg.285)
Which route of administration is primarily used for allergy testing and to administer local anesthetics?
Intradermal route (Pg. 285)
Which medications are known to be effective when administered via the IO route?
amiodarone, epinephrine, atropine, sodium bicarbonate, dopamine, dobutamine, lidocaine (Pg. 286)
When is administration of medication through the ET tube reserved for?
Situations in which an IV or an IO cannot be established (Pg. 286)
Which medications can be administered by the ET tube?
naloxone, atropine, vasopressin, epinephrine, lidocaine (Pg. 286)
True or False:
During administration of the ET tube route, 2 to 2 1/2 times the recommended IV dose (diluted in 10 mL of normal saline) is recommended.
True (Pg. 286)
What is the acronym NAVEL used for, and what does it stand for?
Medication administered through the ET tube via the pulmonary route
Naloxone Atropine Vasopressin Epinephrine Lidocaine
(Pg. 286 NOTE)
Why is Topical Route -Nasal so effective and easily administered?
Intranasal results in rapid absorption of the medication into the bloodstream and cerebrospinal fluid. Manages seizures, pain, hypoglycemia, opiate overdose, and other medical conditions (Box 13-9) (Pg 286)
The rate at which distribution of a drug occurs depends on what?
Distribution depends on the permeability of capillaries to the drug molecules. (pg. 286)
Where are drugs generally first distributed to?
Organs that have a rich blood supply (Heart, Liver, Kidneys, and Brain) (Pg. 287)
What are the two general processes that create drug reservoirs?
Plasma protein binding
Tissue binding
(Pg. 287)
As a drug enters the circulatory system, they may attach to plasma proteins (mainly albumin). What is this called?
Drug protein complex (Pg. 287)
More info: A drug bound to plasma protein is pharmacologically inactive
An anatomical-physiological feature of the brain thought to consist of walls of capillaries in the central nervous system and surrounding glial membranes; its function is to prevent or slow the passage of chemical compounds from the blood into the central nervous system
Blood-brain barrier (Pg. 287)
More info: Only permits lipid-soluble drugs
A protective biological membrane that separates the blood vessels of the mother and the fetus
Placental barrier (Pg. 287)
What’s the difference between the blood-brain barrier and the placental barrier?
Placental barrier allows the passage of certain non-lipid soluble drugs (steroids, narcotics, anesthetics, and some antibiotics). (Pg. 287)
Process in which drugs are chemically covered to metabolites (smaller components)
Biotransformation (metabolism) (Pg. 287)
What tissues are involved during drug metabolism to “detoxify” a drug and render it less active?
Liver (primary site), plasma, kidneys, lungs, and the intestinal mucosa (Pg. 287)
The elimination of toxic or inactive metabolites, primarily by the kidneys; the intestines, lungs,and mammary, sweat, and salivary glands also may be involved
Excretion (Pg. 288)
What factors influence the action of drugs?
Age, body mass, gender, pathological state, genetic factors, environment, and time of administration (Pg. 289)
Why are children who weigh less than 150 lbs and are less than 18 years old always based on body mass for drug doses?
The average adult drug dose is calculated on the basis of drug quantity needed to produce a particular effect when administered to 50% of the population. This population includes only persons between the ages of 18 and 65 who weigh about 150 lbs (68kg) (Pg. 290)
What is the study of how a drug acts on a living organism?
Pharmacodynamics (Pg. 290)
A chemical interaction between the drug and various receptors throughout the body is what common form of drug action?
Drug receptor interaction (Pg. 290)
Drug receptor interaction term:
The propensity of a drug robbing or attach itself to a given receptor
Affinity (Pg. 290 Box 13-10)
Drug receptor interaction term:
The ability of a drug to initiate biological activity as a result of binding to a receptor site
Efficacy (intrinsic activity) (Pg. 290 Box 13-10)
Drug receptor interaction term:
An agent that combines with different parts of the receptor mechanism and inactivated the receptors so that the agonist cannot be effective regardless of its concentration
Noncompetitive antagonist (Pg. 290 Box 13-10)
Drug receptor interaction term:
An agent that binds to a receptor and stimulates some is its effects but may antagonize the action of other drugs with greater efficacy
Partial antagonist (Pg. 290 Box 13-10)
Range that is based on the concentration that provides the highest probability of response with the least risk of toxicity
Therapeutic range (Pg. 291)
Plasma level profile terms:
Duration of action
The period from onset of drug action to the time when a drug effect is no longer seen (Pg. 291 Box 13-11)
Plasma level profile terms:
Loading dose
A bolus of a drug given initially to attain a therapeutic plasma concentration (Pg. 291 Box 13-11)
Plasma level profile terms:
The amount of drug necessary to maintain a steady therapeutic plasma concentration
Maintenance dose (Pg. 291 Box 13-11)
Plasma level profile terms:
The lowest plasma concentration that produces the desired drug effect
Minimum effective concentration (Pg. 291 Box 13-11)
Plasma level profile terms:
Onset of action or latent period
The interval between the time a drug is administered and the first sign of its effect (Pg. 291 Box 13-11)
Plasma level profile terms:
Peak plasma level
The highest plasma concentration attained from a dose (Pg. 291 Box 13-11)
Plasma level profile terms:
Termination of action
The point at which the effect of a drug is no longer seen (Pg. 291 Box 13-11)
Plasma level profile terms:
The plasma concentration at which. Drug is likely to produce serious adverse effects
Toxic level (Pg. 291 Box 13-11)
The time it takes to metabolize or eliminate 50% of a drug in the body
Biological half-life (Pg.291)
A drug is considered to be eliminated from the body after how many half-lives have passed?
5 (Pg. 291)
Measurement of the relative safety of a drug
Therapeutic index (TI) (Pg. 292)
What is the difference between Lethal Dose 50 (LD50) and Effective Dose 50 (ES50)?
LD50 is the dose of a drug that is lethal in 50% of laboratory animals tested. Whereas, ED50 is the dose that produces a therapeutic effect in 50% of a similar population.
TI=LD50/ED50
(Pg. 292)
When a drug is “fairly safe”, it has what kind of TI range?
Wide (Pg. 292)
Example: naloxone has a wide margin between the effective dose
What are some aspects that can affect drug potency and effectiveness?
Temperature, Light, Moisture, and Shelf life (Pg. 293)
What are the components of a drug profile?
Drug name: generic, trade, etc.
Classification: group to which drug belongs
Mechanism of action: way drug causes its effects
Indications: condition for which drug is administered
Pharmacokinetics: how body handles drug
Side/adverse effects: Undesired effects
Dosages: Amount of drug robbery administered
Routes: how drug is given
Contraindications:
Special considerations:
Storage requirements:
(Pg. 293-294)
Pregnancy Category Ratings for Drugs:
Either (1) studies in animals have revealed adverse effects on the fetus and there are no controlled studies in pregnancy women or (2) studies in women and animals are not available. Drugs in this category should only be given if the potential benefit justifies the risk to the fetus.
Category C (Pg. 295 Box 13-13)
Pregnancy Category Ratings for Drugs:
Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester, and there is no evidence of risk in later trimester; the possibility of fetal harm appears to be remote.
Category A (Pg. 295 Box 13-13)
Pregnancy Category Ratings for Drugs:
Either (1) animal reproductive studies have not demonstrated a fetal risk but there are no controlled studies in pregnancy women or (2) animal reproductive studies have shown an adverse effect (other than decreased fertility) that was not confirmed in controlled studies on women in the first trimester, and there is no evidence of risk in later trimesters
Category B (Pg. 295 Box 13-13)
Pregnancy Category Ratings for Drugs:
There is positive evidence of human fetal risk, but the benefits for pregnant women may be acceptable despite the risk, as in life-threatening diseases for which safer drugs cannot be used or are ineffective. An appropriate statement must appear in the “Warnings” section of the labeling of drugs in this category
Category D (Pg. 295 Box 13-13)
The term “clearance” refers to the complete:
Removal of a drug by the kidneys (Pg. 289)
Pregnancy Category Ratings for Drugs:
Studies in animals or human beings have demonstrated fetal abnormalities, there is evidence of fetal risk based on human experience, or both; the risk of using the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are of may become pregnant.
Category X (Pg. 295 Box 13-13)
