last part of pharmokinetics that involves removing drugs from the body.
Excretion.
T or F. Drugs will continue to act until they are metabolized or excreted.
True
The rate of excretion determines drug __ __.?
drug blood level.
Some drugs undego reabsorption after renal filtration. what type of drugs are more easily reabsorbed back into circulation.
non ionized, lipid soluble.
where is the primary site for drug excretion?
the kidneys
Weakly basic drugs are excreted better with slightly __ filtrate.
acidic
Weakly acidic drugs are excreted better with slightly __ filtrate?
basic
What lab values indicate renal impairment?
BUN, Creatinie, GFR (glomular filtration rate)
Patients with renal impairment will have diminished ability to excrete medications and may retain drugs for extended periods. How will this affect the drug doses prescribed to the patients ?
the doses will have to be reduced to prevent drug toxicity
Drug excretion is dependent on urine __?
urine PH
along with urine excretion, where else can drugs be excreted?
Glandular, pulmonary, fecal and bilary excretion
This type of excretion invovles being excreted through gases and volatile liquids. Most of the excreted is unmetabolized. Resp rate and blood flow affect this excretion.
Pulmonary excretion
This type of excretion involves excretion through saliva, sweat, and breast milk. Pt can sometimes taste and smell drugs during excretion
Glandular excretion
This type of excretion involves bile recirculated via enterohepatic path. Prolongs drug activity.
Fecal/ Bile excretion
The theraputic response of most drugs depends on their concentration of __?
plasma
the __ estimates the duration of action for most medications or the length of time required for the plasma concentration of a drug to decrease by one half after it is administered.
Half-life.
What does a repeated dosing of a drug allow?
It allows for a plateau drug plasma level to be reached.
For acute needs, what type of half life is desireable
A short half life.
this type of half life leaves the body quickly (4-8) hours. Minimum effective concentration will drop between dosages.
Short half life
this type of half life leaves the more slowly- 24 hours. Greater risk for accumulation and toxicity. Takes a longer time to reach a steady state.
Long half life.
The amount of drug required to produce theraputic effects
Minimum effective concentration.
the range where the drug produces its desired effect.
Therapeutic range. After peaking, drug plasma level falls due to excretion.
Level of drug that results in serious adverse effects
Toxic concentration
What is the nurses goal involving Time-response relationship?
Nurses want to keep administered drugs withing therapeutic range.
Regarding plasma half life, plasma concentration decreases by how much?
1/2
Once the drug in disontinued, it takes approximately __ half lives until elimination
4
How many half lives does it take to reach optimum plasma concentration/ plasma plateau?
4
This dose is given in higher amt to "prime" the blood stream.
Loading dose
this dose is to keep connentration within theraputic range.
Maintenance dose.
Always taken before the next dose. Peak at peak action per drug guide. It represents the lowest level of drug in body.
Trough
What would be the purpose of giving a loading dosem followed by a maintenance dose. For this, you would often need drugs with longer half lives.
You would be able to reach the plateau faster.
What the drug does to the body
Pharmacodynamics.
Dose in the middle of the curve.Produces effective response in 50% of patients. Standard dose for the drug.
Median effective Dose.
What does a frequency distribution curve show?
Some patients get the desired effect at very low dosages while others need a much higher dosage.
this predicts the therapeutic response in 50% of the patients.
Average dose
The dose of the drug that will kill 50% of a group of animals.
LD 50 (median lethal dose)
Describes the drugs margin of saftey.
Therapeutic index (TI)
Desired drug response in 50% of subjects?
Effective dose (ED50)
What does a high TI mean?
That the drug is alot safer
The difference between LD and ED equals TI. what does this mean
The larger the difference, the greater the TI and the safer the drug will be.
A low TI indicates what?
That the drug needs to be closely monitored because it is not as safe.
Describes how the actions of a drug change with increasing dose. involves 3 phases
Dose response relationship
phase of the dose-response relationship in which few target cells are affected.
Phase 1- the lowest phase.
phase of the dose-response relationship that is has the most desirable range.
Phase 2. It is true here that a higher dose equals more effect.
phase of the dose-response relationship in which the plateau is reached.
phase 3. At this phase, increasing the dose will not increase theraputic effect. Increasing dose could cause adverse effects/toxicity.
compares doses of 2 different drugs evaluating which has a theraputic effect @ lower dose
Potency. Drug in the same class can differ in potency and efficacy.
The greatest maximal response produced by a drug. also compares disired theraputic effect of two drugs.
Efficacy. ex) Morphine has a higher efficacy than ASA.
Most drugs produce their actions by activating or inhibiting specific cellular __?.
receptors
Medications bind to __ which is the target for the drug.
receptors. Drug receptor binding is like lock and key. Most drugs enhance or inhibit a physiological process.
Predicts that the response of a drug is proportional to the concentration of receptors that are bound or occupied by the drug.
Receptor theory.
Once occupied, the receptor triggers a second messenger, these cause...?
Biochemical events to occure causing the frug to stimulate or inhibit activity.
Mimic or enhances the action of endogenous (what's already there) substances.
Agaonists. the response may be greater than endogenous activity. ex) beta 2 cells (lungs) enhance bronchiole dilation.
Produces weaker action than endogenous substance
Partial agonist.
A drug that will occupy a receptor and prevent the endogenous chemical from binding to produc action and may also compete with agonist.
Antagonsit. these are useful in blocking excess enogenous activity and may reverse adverse effects of over doses.They also do not have intrisic activity.
