pharm D2 Flashcards
pharmokinetics
pharmokinetics is the study of the effect of a body on a given drug . > this is via determining the amt of the drug in the body at any given time after adminitstration.
it allows us to determine proper dose and dosage interval to achieve a desired therapeutic drug concentration.
Pharmokinetics describe the impact of a drug on the body as a function of time. at what time can we determine the concentration of a drug?
Using pharmkinetics principles, we are able to determine the concentration of a drug in the body at an given time after administration.
drug presence in the body often follows described/ studied patterns such as that of zero-order or frist order kinetics. Most drugs act according to first order kinetics where a constant FRACTION of the drug is removed per unit of time.
what is zero order kinetics?
zero order kinetics describes the pattern of drug removal from teh system where a certain set AMOUNT of drug is removed per unit of time (example, ethanol.. ) this is in contrast to first order kinetics where a certain FRACTION of the drug is removed per unit of time (half life is a unit used here)
T/F in considering the drug effect on the body,. we consider the concentration of the drug in the blood to be proportional to the amount of effect on the body.
True. It is assumed that the concertration of the drug in the blood is proportional to the efect on the body
what is the difference bt plasma and serum?
Plasma is the liquid porton of blood without rBS (still has clotting factor), while serum is the liquid portio of lood without RBC and without clotting factor (so, plasma without clotting factor)
how many phases of drug clearnace are there?
there are 2 phases of drug clearance, The first is rapid- alpha= the redistribution phse. calculations are not concerned at all with alpha.
more important for calucilations is Beta, the second phase. Beta describes the nature of the clearnace (zero or first order, details..).
Beta describes the initial concentration of the drug admisnistered S well as the half life of the drug
what two parameters does the beta phase of drug clearance describe?
the Beta phase (the 2nd or 2 phases of drug cleanrace) allows extrapolation of the initail concetration of the drug adminiteaterd, as well as the half life of the drug.
There is a formaula that relates concentration per amount time to the half life of the drug. Is the elinimation constant of the formula proportional or the inverse to the rate of elimination of the drug?
the kinetic constant (which relates the rate of durg eliniation of half life) is PROPRTIONAL to the rate of drug elimination. The faster the drug is eliminated from the system, the larger the value of Ke.
what is the equation that relates the rate of eliminiation of a drug to the half life of the drug?
0.693= (Ke) x ( T 1/2)
what do nicotinic receptors impact?
nicotinic receptors impact ion channels = ionotropic
nicotinic receptors are found in all pregangklionic sites
what do muscarinic receptors impact?
muscarinic receptors impqct/alter metabolism =metabotropic. muscarinic receptors are found in parasymtph, post-ganglionic sites
what kind of receptors are syumpathtetic post ganglionic sites?
sympathtetic post ganglionic sites have adrenergic receptos (4 types of importnace here are alha 1,2 and beta 1,2)
what is an agonist?
an agonsit is a compound that activates a receptor. the opposite is an ANTAgonsit that inhibits a receptor/ blocks the receptor
name some factors that alter drug absorption
there are a lot of factors that can alter drug absorption. —
- the time of administration (bf/after dinner, etc)
- GI dysfunc inhibits absorption
- age (older = increased dysfunc body systems)
- environment (such as of bofy- other drugs, etc in the system)
- distribtuion of drugs (body weight, composition,etc)
what is CYP and what are its activators? - and what does this mean?
CYP (most common, CYP3A4 = cytochrome P = oxidizing enzyme.
CYP involved in >50% drug metabolism, via oxidizing drugs thereby eventually inactivating them via glomerulus/renal excretions of ions
CYP activation = metabolism of drug
CYP inactivation = drug stays in body system longer *confounds expected rate of drug metabolism so that body does is higher than what clinically claculated for = bad.
CYP activators = phenytoin, phenylbarbitol, St.Jhn;s wort, rifampin
CYP inactivators = grapefruit juice, some anti- -bacterials, -fungals, histamines.
