Pharmokinetics Flashcards
What is pharmokinetics ?
The study of drug movement throughout the body
What happens to drug as it moves through the body
why is it important to know pharmokinetics ?
help maximize beneficial effects and minimize harm
What do all phases of pharmokinetics require ?
movement- get to the site of action , get to site of metabolism, get to site of elimination
What are the 3 ways a drug can pass through a cell membrane ?
- through channels and pores ( small compounds like minerals and electrolytes )
- Passage using transport systems ( PGP=P glycoprotein , multi drug transporter
- direct penetration of membrane - most common way but drug has to be lipid soluble, meaning lipophilic
Ions are molecules that contain
a net electrical charge
what is a quaternary ammonium compound ?
will always have a positive charge and will contain at least one atom of nitrogen
What is pH dependant ionization ?
Acid is a proton donor ,will ionize to basic ( alkaline )
Base is a proton acceptor , will ionize in acidic media
What is pH partitioning ?
AKA ion trapping, acidic drugs accululate on the alkaline side, basic drugs accumulate on the acidic side
what is absorption ? and what will it determine ?
movement of a drug from administration site to the blood, it will determine how soon there will be effects and the amount will show how intense these effects will be
what are some of the factors that will impact drug absorption ?
Rate of dissolution
Surface area
Blood flow
Lipid solubility
pH partitioning (Ion trapping
What are the enteral routes of administration ?
sublingually, oral( most preffered) and rectal
what are the parenteral routes of adminstration ?
intravenously, intramuscularly, subcutaneously
oral administration is usually in the form of ?
tablets, enteric coated preparations, sustained release preparations
distribution is ?
movement of drug throughout the body
the blood flow will determine ?
The rate of delivery of the drug
how can abscesses and tumours impact drug distribution
solid tumours have limited blood supply and low limited blood flow will impact therapy
with capillary beds, drugs will pass which way ?
They will pass between capillary beds instead of through them to exit the vascular system
What is the problem with the placenta for drug transfer ?
membranes of the placenta are not an absolute barrier to drugs, movement is the same as other membranes
what is the most important plasma protein for drugs ? why is this ?
albumin, which always remains in the blood stream and can impact drug distribution and can result in drug interactions leading to toxicity
true or false drugs can form irreversible bonds with some proteins ?
FALSE - drugs can form reversible bonds with some proteins
most drugs must enter cells in order for what to take place ?
metabolism and excretion
true or false, some drugs must enter the cell in order to each the site of action ?
True
do drugs need to cross the cell membrane to access the receptors ?
No because they are located usually on the surface of the membrane
one of the most common ways drugs produce their effects is by ?
bind to the receptors on the external surface on the membrane
what is another name for drug metabolism ?
bio transformation ( when the chemical structure of the drug is altered
biotransformation takes place where
Usually in the liver
cytochrome P450 is what ?
enzyme needed to metabolize drugs in the liver
what are some of the consequences of drug metabolism ?
Drug inactivation
Increased therapeutic action
Activation of prodrugs
Increased or decreased toxicity
Accelerated renal drug excretion- Most important
What is enterohepatic re circulation
Repeating cycle in which drug is transported
From the liver into the duodenum (via the bile duct)
Back to the liver via the portal blood
enterohepatic recirculation happens only with drugs that have
have undergone glucuronidation
What should be considered for drug metabolism ?
Age( older adults have a slower metobolims, kids have not yet fully developped the liver so they are more sensitve to drugs
Induction of drug-metabolizing enzymes
P450 inducers – INCREASE Metabolism
P450 inhibitors – DECREASE Metabolism
First-pass effect
Nutritional status
Competition among drugs
What is excretion ?
This can be defined as Removal of drugs from the body
What are some of the ways drugs can exit the body ?
through urine, sweat, saliva, breast milk, or expired air
Organ responsible for excretion ?
the kidneys
What are the steps in renal drug excretion ?
Glomerular filtration
Passive tubular reabsorption
Active tubular secretion
factors that can modify renal excretion ?
pH-dependent ionization
Competition for active tubular transport
Age
What are the non renal route of drug excretion
Lungs (especially anesthesia)
Sweat/saliva (small amounts)
Bile
breast milk
What is the half life of a drug ? what does it determine?
Defined as the time required for the amount of drug in the body to decrease by 50%- will determine the dosing interval
duration of effects is determined by ?
combination of metabolism and excretion
drugs that are above the minimum effecrive dose, there will be ?
a maintenance of the therapeutic response
drug levels produced with repeating doses
still unlcear on the graph
