Module 3 Flashcards
Ch. 4,5
what is absorption
movement of a substance from administration site across body membranes, to circulating fluids
what is dissolution
how quickly a drug disintegrates and disperses into simpler form- which makes it more bioavilable
distribution
the process of transporting drugs through the body after they have been absorbed or injected
excretion
removing drugs from the body
metabolism
process of chemically converting a drug to a form that is usually more easily removed from the body
pharmacogenomics
study of genetic variations that influence an individual’s response to drug therapy
pharmacokinetics
study of drug movement throughout the body, how a body handles medications
why do nurses care about pharmacokinetics?
we need to know how a drug is supposed to act and what it looks like if a drug is working or not. it is important to know how fast a drug can get absorbed, how it gets distributed in the body etc.
What are some barriers that medications face as they pass through our systems? These barriers can impact how much of the drug actually works in our bodies.
- Acid, digestive enzymes, in the stomach and liver
- Blood- brain barrier
- Proteins- some drugs are protein binding
- Membranes (that coat linings in our bodies) Ex) intestines
what are the 4 pharmacokinetics processes
absorption, distribution, metabolism, excretion
Name two ways that drugs pass through membranes in the body and describe, in your own words, what they mean.
- Active transport: energy is required for this drug to get through the membrane
- Diffusion or passive transport: does not need energy, but chemical (drug) moves down the concentration gradient
Drugs that are lipid soluble pass through membranes in the body more easily than drugs that are not lipid soluble. What is the reason for this?
It is more likely to get through the barrier. The head is hydrophilic which means it likes fat- therefore fat is easy to get through this layer. Water is much harder to pass through this layer because again, fat and water don’t like each other.
Small molecules such as urea and alcohol can pass easily through pores in the plasma membrane, and large molecules do not pass easily through those same membranes. What is another way for those large molecules to influence those target cells?
They can bind to receptors on the outside of the cell membrane which activates second messengers which can produce a change.
What is the primary pharmacokinetic factor that determines the length of time it takes a drug to produce an effect? Why do you think this is?
ABSORPTION! if we don’t absorb it, there won’t be any impact in the body
Ex) transdermal patch over a scar= won’t absorb
There are numerous factors that affect absorption. What are those factors?
drug formulation, dose, route of administration, size of drug molecule, surface area of the absorptive site, digestive motility, blood flow, lipid solubility of drug, ionization, pH
explain how drug formulation affects absorption
the form of the drug helps determine how quickly it is absorbed. liquids (orally) are absorbed much faster than tablets
explain how dosage affects absorption
a higher dose of a drug is absorbed faster
explain how route of administration affects absorption
IV administrations are much faster absorbed
explain how size of drug molecule affects absorption
Size of drug molecule: larger drug molecules take longer to absorb than smaller ones
explain how the surface area affects absorption
the larger surface area, the faster absorption
explain how digestive motility affects absorption
changes in GI motility (capability of motion) can speed up or slow down absorption.
Ex) when you have diarrhea or take a laxative, your intestinal motility speeds up very quickly. If you have a drug in there, it won’t get absorbed as much because it is going through your system so fast- doesn’t have time to absorb
explain how blood flow affects absorption
greater blood flow to the site allows for faster absorption. you need blood flow for something to get absorbed
explain how lipid solubility of drug affects absorption
lipid-soluble drugs are absorbed faster than water-soluble drugs
explain how pH affects absorption
how acidic of basic it is
what does ionization mean
It gains a charge. It either gets an electron or releases an electron. You take an aspirin and goes into the stomach. It gains a charge because it is in an acidic environment, and it doesn’t get absorbed because it is now ionized. The enteric coat prevents it from dissolving in the stomach and allows it to dissolve in the intestine- there isn’t any acid in the intestine.
How can PH levels impact the ionization of a medication?
Briefly explain what happens to aspirin when it leaves the acidic environment of the stomach and enters the alkaline environment of the small intestine.
It impacts the absorption.
The aspirin becomes ionized in the digestive tract. In an ionized form, it is not as likely to be absorbed and distributed to cells
how can drugs impact the absorption of a medication?
some block absorption. Ex) tetracycline, when it is taken with calcium or magnesium the tetracycline does not get absorbed because it interacts with magnesium and calcium. (Mg, Ca can significantly delay the absorption of a drug, so you should not give tetracycline with calcium or magnesium supplements
how can food impact the absorption of a medication?
high fatty foods delay the emptying of your stomach
how can your stomach impact the absorption of a medication?
depending if it is full or empty could delay the absorption of a drug or medication
Why would a patient who takes a laxative impact the absorption of another drug?
If meds pass through fast, they don’t have time to absorb.
Explain the pathway for the distribution of medication.
IV drugs goes right into the blood, inhaled drugs go right to the lungs
What elements impact the body’s ability to transport medication around the body?
BLOOD FLOW!
Some places in the body can hold onto drugs. What are some of those places? What is an example of a medication that would build up in your teeth?
skin, bone, adipose tissue, teeth
ex) tetracycline is an antibiotic that could build up in teeth. it should never be given to children because of how they are growing and their bones. If it gets in there system, it can cause teeth to be gray or discolored.
Ex) Anesthesia- obese people hold on to the gas longer because the adipose tissue absorbs it
Some drugs have an affinity (love) for proteins that are in the bloodstream. When they bind to proteins, they cannot affect the target organ. Why is this important to know?
proteins will attach to the protein in the blood, and whatever part of that drug attaches to the protein won’t work because it’s attached to the protein.
Ex) couminin- blood thinner, anticoagulant, when you take it, it has a 99% affinity for proteins (99% will bind, leaving 1% able to absorb)
how could low albumin(protein) levels cause someone to have aspirin toxicity?
If someone doesn’t have a lot of protein in their blood and they take a drug that has 99% affinity and you don’t have much protein in your blood, more of that drug is floating around in your body which could lead to toxicity. *too much of the drug is working in your body.
Some foods and other drugs compete for protein-binding sites. When this happens, one drug is more potent in the body. Why is this important to know?
If you are given two drugs with 99% affinity, one of the drugs could ‘kick’ the other off and ‘win’ or dominate. This could lead to blood toxicity since only one of the drugs will bind to blood. Then there would be too much of one drug in the body= toxic.
what does addition mean?
the action of drugs sum together as a total. Combined effect of two drugs equals the sum of their individual effects.
what does synergism mean?
the action of drugs result in a potentiated or greater than additive effect. Some drugs are synergistic to other drugs. Ex) alcohol and pain med= act upon each other and give you a greater impact
what does antagonism mean?
the action of one drug blocks or has opposite effects of the other drug
what does displacement mean?
when one drug removes another drug at a protein-binding site, which alters the desired effect. It makes the displaced drug more active.
explain the blood brain barrier
anatomical structure that prevents certain substances from gaining access to the brain
explain the fetal-placental barrier
special anatomical structure that inhibits entry of many chemicals and drugs to the fetus
what does metabolism mean as far as medications go?
process of chemically converting a drug to a form that is more easily removed from the body. It also involves complex pathways that alter drugs and minerals
why is it important for nurses to check a patient’s liver and kidney function prior to administering medications?
- liver and kidneys are primary areas for drug metabolism. they have high metabolic rates
- if liver isn’t working, it can’t break down meds and the meds stay in body longer and become toxic.
- if kidneys aren’t working, they can’t excrete drugs
what is the primary source for drug metabolism in the body?
liver
what is enzyme induction?
the ability to increase metabolic activity
what is enzyme inhibitor?
the ability to reduce metabolic activity in the liver, so the liver would break down things slower
what routes are drugs eliminated from the body?
feces, bile, urine, sweat, saliva
(lungs, liver) RENAL= primary
can drugs be excreted through breast milk?
YES, this is why it is important for pregnant women to avoid certain drugs and alcohol. The fetal-placental barrier allows for these chemicals to pass through
What determines the duration of action of a medication?
Drug concentration (how much of that drug is given), dosage- how often you give it, route, drug and food interactions, drug supplement interactions. Drug herbal interactions, drug to drug interactions and plasma half life
describe minimum effective concentration
the amount of drug is required to produce a therapeutic effect
describe toxic concentration
the level of drug that will result in serious adverse effects
describe therapeutic range
the drug concentration between the minimum effective concentration and the toxic concentration
onset of drug action
amount of time it takes to produce a therapeutic effect after drug administration
peak plasma level
when medication has reached its highest concentration in the bloodstream
duration of drug action
amount of time a drug maintains its therapeutic effect- there are multiple factors that impact the duration of drug action
plasma half life
the length of time required for a medication’s plasma concentration to decrease by one- half after administration. Drugs with a short half-life have to be taken more often, as the effect in the body does not last as long.
loading dose
a higher amount of a drug, usually given only once or twice to ‘prime’ the bloodstream with a sufficient level of drug. *particularly important for drugs with prolonged half-lives and for situations in which it is critical to raise the drug plasma levels quickly
maintenance dose
they keep the plasma drug concentration in the therapeutic range
why is the half-life of a medication important to know?
it is important to know how long the drug stays in the body and how often drugs can be taken again. The longer the half life, the longer it will take to leave your body
i. At 0 hours (initial dose): 100 mg
ii. After 10 hours (1st half – life): 50 mg (half of 100)
iii. After 20 hours (2nd half-life): 25 mg (half of 50)
iv. After 30 hours (3rd half life): 12.5 mg (half of 25)
v. After 40 hours (4th half-life): 6.25 mg (half of 12.5)
before giving a medication, which two organs would you want to know the health of before giving the medication?
kidneys and liver
what is the definition of pharmacodynamics? Why do we, as nurses, care about this?
how a medicine changes the body- why it does in the body
Nurses must know whether or not a drug will produce a significant change in patients. You won’t be able to assess it the drug is working. You won’t know what to look for for side effects.
what are the three phases of determining a therapeutic response?
phase 1- lowest dose
phase 2- desirable range
phase 3- plateau
describe phase 1 in a therapeutic response
lowest dose, if we don’t have enough drug on board, it is not going to do anything, there is no effect
describe phase 2 in a therapeutic response
desirable range, therapeutic, we are getting enough on board and we gotta keep it right there!
describe phase 3 in a therapeutic response
plateau, you could give more of that med and nothing will change. If I take more of this drug, will that be better? No! the more you take will not give you more impact. When people are at the plateau, they can devolve toxicity.
*Know that people respond to medications in different ways. A dosage of one drug might impact one person in one way and another in another way.
Genetics
how do you determine whether an average dose is effective for a patient? What would you assess?
you would need to know what to look for. you would assess by knowing what should be happening and what the patient might be experiencing- how will I know if the meds are working?
when a patient is given a dose of medication and they reach phase 3, a plateau is reached. What would you say to a patient that said “If I take more, I will have a better effect?”
no, that not true. You get to a certain point where the medication can’t do anymore in your body, so giving you more won’t provide any therapeutic benefits. You can harm yourself if you take too much.
potency
strength of a drug, a specific concentration or dose. A drug that is more potent will produce a therapeutic effect at a lower dose, compared with another drug in the same class. Potency is one way to compare the doses of two independently administered drugs in terms of how much is needed to produce a desired response.
efficacy
the magnitude of maximal response that can be produced from a particular drug
which is more important; efficacy or potency?
efficacy is almost always more important than potency
agonist
to stimulate
partial agonist
kinda stimulate, but not as much as agonist
antagonist
to block
duration of drug action
time period during which a drug produces its therapeutic effect
agonist-antagonist
blocks and stimulates
affinity
the strength of binding between a drug and its receptor
median effective dose
(ED50)
the dose of a drug that produces a therapeutic effect in 50% of the population
median lethal dose
(LD50)
dose of a drug that is lethal to 50% of the population
median toxicity dose
(TD50)
dose of a drug that produces toxic effects in 50% of the population
conjugates definition
chemical compound formed when a drug is combined with another substance, often to enhance excretion
drug- protein complexes
formed when drugs bind to plasma proteins that affect their distribution and action
