Upgrade to remove ads
Pharm Ch. 4
Terms in this set (75)
motion of drugs throughout the body
source of major differences in responses to drugs
Examples of Individual Variances
All stages of drug movement through the body require molecules to cross...
Four Major Pharmacokinetic processes
What do the four processes determine?
concentration of a drug at its site of action
3 ways to cross cell membrane
1. passage through channels or pores
2. Transport Systems
3. Direct Penetration**
Passage thru channels
very few drugs can do this
must be very small
usually proteins in the cell membrane that move a drug molecule in or out of a cell
drug must be lipophilic
What 3 things must drug be to directly penetrate cell membrane?
Why is it important that the drugs are lipophilic, non-ionized, and non-polar?
Cell membrane is non-ionized and non-polarized
LIKE DISSOLVES LIKE
Amount of drug absorbed influences what?
Rate of absorption influences what
how soon effects of drug will show
site of administration to the blood
PO meds take how long to show effects?
What is the path of PO meds?
Go through GI to be absorped
Hepatic Portal System
Liver for metabolism
Factors that affect absorption
route of administration
rate of dissolution
How do IV get absorped?
Immediate absorption into blood
into blood directly
effects are immediate
What two forms can weak acid or weak base exist in?
ionized or non-ionized
Whether the drugs ionize or stay in uncharged form depends on what?
the pH of the surrounding environment
Where do acids ionize?
Where do bases ionize?
Once a drug is ionized can it cross membranes?
What do drugs want to do?
ionize so concentration gradient moves drug into the blood which is more basic
By feeding tube
Which route is preferred? Why?
IM is used mainly for what?
When is IV used a lot?
What three things does distribution depend on?
1. Blood flow to tissues
2. Ability of drug to leave vascular system
3. Ability of drug to enter cells
Is Blood Flow to tissues usually an issue in distribution?
no only with tumors and abscesses
Ability of drug to leave vascular system
affected by albumin protein binding
AND tightness of capillary junctions
Ability of drug to enter cells
this only applies to drugs that exert their effect INSIDE target cell
How do most cells interact with target cells?
most drugs fit into receptor sites on the SURFACE of cells
If a drug is ionized, does it have trouble leaving the blood? Why?
leaves through gaps
What mainly affects drug leaving the blood?
Why is it hard for drugs to pass the BBB?
very tight junctions
P-Glycoprotein to help drug exit
What is the most common carrier protein?
Can albumin leave the capillaries? Why?
No, it is too large
drugs attached to albumin are trapped in blood
Binding strength of drugs to albumin
different drugs have different strengths of binding
ex: warfarin 99% bound
What drug molecules can exit the capillaries?
Free drug molecules must leave to reach site of action
What does albumin do?
Helps drugs move through blood
ideally lets go of drugs so they can exit
If albumin doesn't let go of bound drug molecules what is the solution?
1. give higher doses
2. find way to break drug-protein complex
Why is exiting the vascular system so easy?
looseness of the endothelial lining of capillaries
What characteristics must CNS drugs have to cross BBB
1. lipid soluble
2. transport system
alteration of drug structure by enzymes
Where does most of metabolism happen
in the liver
What is Cytochrome P450 System ?
enzymes that promote metabolism in liver
CYP1, CYP2, CYP3
Possible consequences of drug metabolism
accelerated renal excretion
increased therapeutic action
activation of prodrugs
What molecules leave the urine the fastest?
How does liver affect metabolism
leads to toxicity
give smaller doses and more spread out
Age variation in metabolism
1 year old liver begins functioning
CYP variation in metabolism
more CYP enzymes = better
some drugs compete for the same CYP system
First Pass Effect
1st pass through through liver drug completely metabolized BEFORE reaching site of action therefor NO THERAPEUTIC effects
What is the solution to first past effect?
use different route
sublingual, topical, IV
Nutritional Status variations in metabolism
Enzymes for metabolism need proper nourishment to work
What is the main organ in excretion?
What are the steps of urine formation
passive tubular reabsorption
active tubular secretion
What are some other ways drugs are excreted?
How does kidney failure affect excretion?
risk of toxicity because less out through kidney and more is left in blood
solution: wait longer between administering doses
most drugs are small enough that they are filtered at glomerulus unless they are bound to ALBUMIN
lipid soluble drugs are mostly reabsorbed into the blood, non-lipid drugs are excreted
some drugs must be actively secreted into the urine
Why are plasma drug levels measured?
due to ease
correlation with therapeutic and toxic effects
Minimum effective Concentration
minimum amount of drug needed to acheive a therapeutic effect
level at which toxic effects occur
plasma drug levels above MEC but below toxic concentration
time required for amount of drug in the body to decrease by 50%
can be dangerous
still give drugs
nurse must monitor closely
T 1/2 determines
Desired plateau plasma level determines
When is plateau achevied?
when amount of drug eliminated between doses equals the dose administered
THIS SET IS OFTEN IN FOLDERS WITH...
Pharmacology Unit 1 Chapter 1
Pharm Ch. 1-3
Pharm Ch 5
Pharm Ch 6
YOU MIGHT ALSO LIKE...
Pharm ch 4
Pharmacology Quiz 1 (pharmacokinetics and pharmaco…
N165- Introduction to Pharmacology- Phamacokinetics
OTHER SETS BY THIS CREATOR
Community Health Final
Psychopharm Test (Names of Drugs with Classes)
Schizophrenia Positive and Negative Symptoms
NURS 431 Midterm