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desired outcome of admin of a drug
3 therapeutic effects of drugs?
Tx s/s, cure, prevent
How are pharmacotherapeutics of a drug determined?
clinical drug trials are sent to the FDA
Off label use of a drug?
using a drug in a way that is not therapeutically OK'd for by the FDA
Should the nurse question off label uses of meds?
When is this OK?
yes, but it is OK if the literature supports use of the drug for other things or the doctor can explain why they are using it
movement of drug particles in the body and the processes that occur during this movement
the effect of the body on the drug
4 phases of pharmacokinetics?
- 1. absorption
- 2. distribution
- 3. metabolism
- 4. excretion
the movement of the drug from the site of admin to the bloodstream
movement from blood -> tissues -> cells
drug is converted into another substance or substances
removal of the drug or drug substance after metabolism
What must occur for drugs to move through the body?
must pass cell membranes
3 ways that drugs pass through cell membranes?
1. pass b/t spaces of channels b/t molecules in the membrane if the drug molecules are very small
2. use transport system that may not require use of enery
3. penetrate the membrane directly - if soluble in lipids
What method of entering cell membranes is the most commonly used by drugs?
Describe a polar molecule.
Can polar molecules penetrate the cell membrane?
There is a neutral overall charge but one end is positive and the other end is negative
no, they are hydrophilic
What are ions?
molecules with a net charge
`process of inducing a molecule to carry a charge
What will happen to acids in a basic environment?
Bases in an acidic environment?
acids give up a positive charge in a basic env and bases accept a positive charge in an acidic env
What will happen to most molecules if they become ionized?
they will not be able to pass through the cell membrane....very small ions can pass through channels but most cannot pass at all
What will occur if the pH on either side of the cell membrane differs?
What is this process called?
the molecules tend to go to the side where they will ionize. Once they get there, they cannot pass back through
ion trapping or pH portioning
How may the movement of drug molecules be altered?
altering the pH on one side of the membrane
What is the completeness of absorption?
the portiuon of the drug that is absorbed
2 factors that affect the rate of absorption?
1. route of admin
2. rate of absorption / rate of dissolution
Route rate of absorption in order?
Large surface area increases/decreases the rate of absorption?
How does blood flow affect rate of drug absorption?
Implications for patients with impaired circulation?
increased blood volume = increased rate of absorption
they do not absorb drugs as quickly as others do
thins that affect the rate of absorption?
- 1. surface area
- 2. blood flow volume
- 3. lipid solubility
- 4. pH differences b/t site of admin and plasma
- 5. physiological condition of the pt
How does pH b/t site of admin and plasma affect drug absorption?
will be absorbed faster if if pH diff. favor the molecules being ionized in the plasma
3 factors that affect the distribution of a drug throughout the body?
- 1. blood flow to the tissues
- 2. drug's ability to leave the blood
- 3. drug's ability to enter cells
2 types of pathophysiologic conditions that are mostly avascular?
1. abscesses - pus-filled pockets surr. by normal tissues
2. solid tumors
Where does the drug leave the vascular space?
in the capillary bed b/t the widely spaced cells here
How do proteins affect the distribution of drugs?
drugs form reversible bonds with proteins/albumin
drug molecules attached to albumin/protein cannot pass through cap walls and will have no effect - drugs that are highly protein bound will require higher doses to have an effect
the bonds are reversible and will eventually dissolve and leave the drug free to act
How does protein-binding of a drug affect its dosing?
What may occur if a person has abnormal protein levels?
drug dosages are calculated based on drug protein-binding ability and normal protein in the body
if protein levels are abnormally low then there will be an abnormal amount of free drug in the body and may overdose
Displacement in relationship to protein binding?
if 2 drugs are given and 1 has more affinity for albumin the other drug will be displaced from the albumin and will be more highly distributed than normal - will need to reduce it's dose
2 ways drugs may cross the BBB?
- 1. lipophilic
- 2. have a transport system
The placental membrane separates ___ from ___.
How does it differ from other membranes in the body in relation to drug molecules passing?
separates maternal and fetal circulation
any molecule that can pass through a membrane can pass through the placenta
In order to pass through the placenta a molecule must be ____, _____, and not ____ ____.
- 1. lipophilic
- 2. non-ionized
- 3. protein-bound
How may hepatic dysfunction affect drug distributuion?
causes less albumin = increased drug free in body
Consideration when giving infants meds that work on brain?
BBB is not fully dev. and drugs may have increased affect
How can malnutrition affect the distribution of drugs?
albumin will be decreased = increased free drug
How may alcohol affect the distribution of drugs?
affects the liver - lower albumin
How may obesity affect the distribution of drugs?
if drugs are highly lipophilic they will go to adipose cells and circulating levels will be decreased
Where does drug metabolism occur?
mostly in the liver
also in the sm int, lungs, kidney, brain, olfactory mucosa, and skin
Pt who have decreased drug metabolism?
What effect does this have?
neonates, children, and older adults
can decrease metabolism and increase adverse effects from the drug
How may malnutrition affect the metabolism of drugs?
may prolong drug effects r/t poor hepatic metabolism
How may obesity affect the metabolism of drugs?
can increase the rate of transformations = need higher drug doses
another term for the metabolism of a drug into other forms
What usually occurs when a drug is metabolized?
drug will be changed from lipophilic to hydrophilic so it can be excreted in the renal system
products of metabolism
drugs that are incative until metabolized into an active form
Most drugs are metabolized into active/inactive form?
What does it mean if a drug is highly metabolized?
every time it passes through the liver in circulation a large number of drug molecules are metabolized
drugs that are taken orally go -> portal vein -> liver where most of the drug will be metabolized and not a lot will circulate
may need higher doses to get therapeutic effect or give by another route so it doesn't go strait to liver
Describe how drug is metabolized in liver based on percetage and number of drug molecules metabolized with each pass?
same percentage of drug molecules will be metabolized with each pass but there will be less number of molecules metabolized with each pass b/c the drug number in body will be decreasing
Cytocrome P-450 system?
enzyme system that predominantly carries out metabolism
Where is most of the P450 system located?
in the liver
How may drugs affect the p450 system?
How will this affect other drugs?
drugs can stim or repress enzyme p450 enzyme synth
this can alter the met. of other drugs/substrates for that enzyme
if the enzyme is increased the drug will be met. faster and their will be less drug circulating
What will occur if 2 or more drugs are met. by the same enzyme?
they will compete for the enzyme and at least one of them will have altered met.
Why does each individual met. drugs differently?
genetic differences is isoenzymes
If a person poorly metabolizes a drug how will this affect the amount of circulating levels of the drug?
What may occur?
the circulating level will be higher than expected
more therapeutic affect and more side effects
What will drug levels be like if a person is a rapid metabolizer?
What may need to be done?
lower than normal circulating levels
How can grapefruit affect the p450 system?
How does this affect drug metabolism?
decreases isoform 3A in the intestines but does not affect the liver amnt
drugs that rely on 3A for met. will have higher levels
What is St John's Wart?
How may it affect the p450 system?
herb for depression
- opposite effect from grapefruit
- (increases 3A)
How may inflammation affect the p450 system?
can increase enzymes and metabolism of drugs
the drugs will be ineffective without higher doses
How may body temp affect the p450 system?
hypothermia can decrease met. of drugs and their effectiveness and can increase adverse affects
Most common route for drug excretion?
GI, sweat, lungs, saliva, breast milk
Major pathophysiologic change that can affect drug excretion? - 3 things that may cause this?
What other body system can decrease excretion if damaged?
- decreased renal functioning:
- 1. decreased CO = decreased perfusion
- 2. elderly
- 3. renal drug toxicity
3 processes involved in renal excretion?
- 1. glomerular filtration
- 2. tubular reabsorption
- 3. active tubular secretion
How does drug get from bloodstream into renal system?
drug enters the glomerulus through caps around it unless they are bound to proteins which are too big to pass through
What occurs during tubular reabsorption of a drug?
When will this not occur?
the conc. gradient of the drug causes it to go from the renal tubule back into the blood stream so that only some of the blood is excreted
this will not occur unless the drug is lipophilic - if the met. of the drug makes it hydrophilic all of the drug will be excreted
What occurs during active tubular secretion of a drug?
active transport systems in the renal tubule move some drugs from the blood into the urine
What 2 types of drug metabolites are hydrophilic and cannot undergo tubular reabsorption?
ions and polar compounds
How can the renal excretion of a drug be encouraged?
How can this be useful?
if the pH of the urine causes the drug to ionize then the drug will be excreted b/c it will not be able to be reabsorbed
urine is acidic and if the drug is basic = ionization and if the urine is made more basic by a drug then it can be made to ionize a toxic acid to encourage its excretion
What may occur is 2 drugs are taken together that both use the active transport system?
How can this be used to advantage?
the drugs will compete for the active transport and be in the system longer than normal
2 drugs may be given together in order to deliberately slow their rate of excretion
Factor that affects excretion of durgs through bile?
How does this occur?
some of the bile that leaves the liver -> intestine is reabsorbed into the portalk circulation and returned to general circulation = drug molecules are reabsorbed
How is it expressed?
amount of time that is required to remove half of the blood conc of a drug\
will always be a percentage
What will happen to the half life a drug if the pt has renal or liver problems?
the half life may be longer
How long does it take for this to be achieved?
the amount of drug coming in matches the amount being excreted
4 to 5 half lives
Can steady state be achieved faster by increasing the dose of the medicine?
no, it is achieved based on the amnt of time required for 4 to 5 half lives to occur
When can the full pharmacotherapeutic response of a drug be measured?
What implications does this have?
once the drug has reached steady state
before adjusting a dose must allow steady state to occur to measure effects of the drug
What may be done if therapeutic effect of a drug is needed quickly and can't wait for steady state?
loading dose = high level of the drug so get therapeutic effect
rate in which the drug is cleared from the circulation
2 major modes of clearance?
renal excretion and hepatic metabolism
biological, chem, and physiologic actions of a drug withing the body and study of how these actions occur
How do drugs cause therapeutic responses?
they turn on/off, promote, or block the body's already existing functions - they cannot make the body do a new function
How do most drugs create their effects in the body?
they attach to cell receptors and stim the cell to act or block other molecules from attaching to the receptor
How do drugs attach to body cell receptors?
using hormones, NT, etc
drugs that attach to a receptor and stim cell to act
drugs that attach to receptors in order to block other stimulatory molecules from attaching
Intrinsic activity of a drug?
drug's ability to stimulate its receptor
How may receptors change?
Why does this occur?
they may be become less sensitive or their numbers can be changed
in response to stim. or inhibition
What can occur if an agonist drug is cont. given?
the receptors are cont stimulated and may become less sensitive
What can occur is an antagonist is cont. given?
stim of the receptor is cont blocked and it may become hypersensitive
How do nonreceptor drugs work?
they interact chem with substances in the body
minimum effect concentration - min. amnt of a drug required to have an effect at all
What will occur with additional dosing after MEC is reached?
response to drug increases as more drug is given until a plateau is reached and increasing the dose will have no effect
What is the potency of the drug r/t?
the amnt of drug that must be given in order to produce a particular response - it pharmacologic activity
r/t to its affinity for receptors
Efficacy of a drug?
What is this r/t?
how well a drug prod. its desired effect
r/t its intrinsic activity
dose that is required to produce the therapeutic response in 50% of the population
is used as the standard starting dose
dose that is admin consistently over time
dose that would be fatal in 50% of the population
relationship of the ED50 to the LD50
Narrow therapeutic index?
The closer the therapeutic index is to ___ the more risk of OD.
the LD50 and ED50 do not differ by much
How is the measured?
dose that reaches MEC but below the level at which adverse effects occur
measure blood levels of the drug
What must be noted if a blood sample is order for drug blood levels?
must note when the last dose was given