Pharmacokinetics Flashcards
What does the effect of a drug depend on
the ability of the drug to travel through the body and reach the brain intact
What does concentration of a drug at the site of action depend on
1) dose administered
2) rate of accumulation/removal from site of action
what is pharmacokinetics
refers to the processes involved in the movement of drugs within biological systems with respect to absorption, distribution, metabolism, excretion
what is absorption
refers to getting the drug from where it is administered to the brain
what are the factors related to the body that affect absorption
Area of absorptive surface
vascularity
pH
presence of other substances
GI motility
functional integrity of absorptive surface
diseases
what are the factors related to drugs that affect absorption
lipid water solubility
molecule size
degree of ionization
physical forms
chemical nature
dosage forms
formulation
concentration
what influences how well a drug passes through a membrane
1) concentration
2) lipid solubility
what is lipid/water solubility
drugs must be hydrophobic enough to cross lipid membrane and hydrophilic enough to dissolve in plasma
what molecules are hydrophobic
lipids, uncharged molecules
what molecules are hydrophilic
charged (polar) molecules
what is the oil-water partition coefficient
the relative solubility between the two media
what does a higher oil-water coefficient mean
molecule is able to pass through the membrane more easily and less easily dissolves in water
what does a lower oil water partition mean
molecule is more easily dissolved in water and less easily passes through the membrane
what is the relationship between barriers and time of effect
the more barriers a drug has to pass through the longer/slower the route of administration is
what is the slowest route of administration
oral
what is the fastest route of administration
inhalation/ intravenous
what is intramuscular administration
into a muscle
what is subcutaneous administration
under the skin
what is intranasal administration
applied to the mucous membranes of the nose
what is sublingual administration
under the tongue
what is transdermal administration
applied to the skin
what is intravenous administration
into a vein
why is oral administration the slowest
the drug must pass through the stomach enzymes/acid and the liver
what is the first pass effect
applies only to drugs taken orally
blood supply to GI tract goes directly to liver then the rest of the body
what factors affect the first pass effect
rate of movement of contents through GI tract
empty stomach
more acidic environment
why is intravenous injection fast
drug passes directly into the blood stream bypassing all the barriers
why are some drugs that are ineffective when taken orally effective intravenously
there is a faster onset and higher concentration of the drug into the bloodstream
what are the disadvantages of IV administration
1) drug has to be soluble
2) weakens veins
3) can get a blood clot formation
4) dangerous (aids, hiv, bacteria)
5) hard to stop overdose if induced with IV
what is the seconded fastest method of administration
intramuscular injection
what is the third fastest method of administration
subcutaneous, sublingual, intranasal
why is inhalation administration effective
lungs have a large surface area and are in close proximity of blood vessels
what is the blood brain barrier
regulates passages of substances from the blood stream to the brain
how can a drug pass through the blood brain barrier
1) tiny
2) active transport system
3) lipid soluble
why should we care about routes of administration
the faster the absorption, the more intense the high
the more intense the high, the more likely you are to get addicted
how does metabolism affect a drug
metabolism may make a drug less active (first pass), more active, or have no effect on drug activity
what is plasma half life
amount of time it takes to eliminate half of the drug from the blood stream
how are most drugs removed from the body
excreted from the kidneys
when are the kidneys most effective
when the concentration of the drug is high
why is excretion of psychoactive drugs slow
they are very lipid soluble
how can excretion of acidic drugs be increased
by making the urine more basic
how can the excretion of basic drugs be increased
making the urine more acidic
