Chs 4-5 Flashcards
(33 cards)
PER IM INJECTION NEVER…
Give more than 3 ml per injection
Pharmacokinetics
What the body does to the drug, how the drug moved into/through and out of body
Pharmacodynamics
What drug does to the body or how to drug works
How the drug is exerting it’s therapeutic effect or how medication changes body to produce s therapeutic effect
PK-order of drug movement through the body
- absorption
- distribution
- metabolism
- elimination
Passive transport/diffusion
Molecules move from area of high concentration to area of lower concentration
Usually small, non-ionized or lipid soluble molecule
Active transport
Need energy (ATP)
Chemicals move against concentration or electrochemical gradient
Usually large ionized or water soluble molecules that have difficulty in bypassing by lipid bi-layer
Absorption
MOVEMENT from the site of administration (oral IV IM) across body membrane to the circulating fluids
Primary PK factor that determines time for drug to produce an effect
IV IS FAST GI IS SLOWER
Distribution
Physiologic movement of drugs from circulation to the tissues; how drugs are TRANSPORTED throughout the body
**how it gets from route of admin.
Go for drug to reach intended tissue site
Factors: Membrane permeability (lipid soluble) Tissue affinity Volume of distribution Protein binding
Blood brain barrier
Protective mechanism for brain and some meds may not be able to pass this barrier
Makes brain tumors difficult to treat
Fetal placenta barrier
No pregnant woman should he given meds without strong consideration of condition
*needs to be approved by OBGYN
Metabolism
Chemically CONVERTS drug so it can be easily removed from the body
LIVER IS THE PRIMARY SITE
-liver metabolized oral drugs before they reach central circulation so oral meds pass through liver first
This is called first pass metabolism
First pass effect
“First passage” of drug through liver after absorption from the GI tract
*why you might have diff dose between IV and oral
ALL ABOUT GETTING DRUG INTO BLOODSTREAM; if this happens you have 100% bioavailability
Pro drug
If drug is this it is inactive until it has been metabolized into active metabolites. First pass metabolism may actually increase activity and reduce time to onset of erects compared to other route of admin.
Ex/codine. -> morphine
What affects bioavailability?
Grapefruit juice (can destroy cytochrome p450 which metabolized meds)
Liver disease (cirrhosis) which destroys liver tissue
Excretion
Primary organ is kidneys
How drugs are REMOVED from the body
Secretion of drugs is less active in infants and elderly
Drug levels are measured in plasma
Therapeutic range= sweet spot
Minimum effective concentration
Amount needed to produce a therapeutic effect
Toxic concentration
Level of drug that can produce serious adverse effects
Too much of it** ALL drugs have side effects
Plasma half life
Length of time needed to decrease drug plasma concentration by 1/2
***reason why some meds you need every 4 hours vs once a day
The greater the half life the greater the time it takes to excrete
Drugs with short half life wear off quickly
Therapeutic range
Plasma drug concentration between minimum effective concentration and toxic concentration
“Sweet spot”
Filtration
Excretion-renal
Free drugs, water soluble agents, electrolytes and small molecules
Secretion
Excretion-renal
Drug protein complexes and large substances
Loading dose
Given to reach steady state more quickly
Higher amount of drug given
Plateau reached faster
Quickly produces therapeutic response
Maintenance dose
Keeps plasma drug concentration in therapeutic range
Therapeutic index
Measure of a drugs safety margin
higher the volume the safer the drug
(More room for error)
Narrow TI drugs require more frequent monitoring
Ex/digoxin-see yellow halos if toxic
