Pharmacokinetics and pharmacodynamics of injected drugs page 8-11
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dose response curve
QUESTION FROM LAST YEAR: WHAT DOES IT DETERMINE
depict relationship between dose of drug administration and resulting effect
DETERMINES SIZE OF RESPONSE WITH CORRELATION TO DOSE
potency or affinity on drug dose response curve and factors that influence it
depicted by the curves location along the dose-axis of the dose-response curve
influenced by absorption, distribution, metabolism, excretion, and affinity for the receptor.
BE ABLE TO PICK OUT MOST POTENT ON GRAPH- TEST FROM LAST YEAR- THIS WILL BE THE CURVE THAT IS CLOSEST TO THE LEFT. THE SLOPE THAT GOES TO THE MAX THE QUICKEST THE MORE TO LEFT THE MORE POTENT THE MORE TO RIGHT THE LESS POTENT
Slope on drug dose response curve
- influenced by the number of receptors that must be occupied for drug effects to occur.
- -the steeper the slope the greater the effect small changes in dosage are likely to produce
- EX:if drug must occupy majority of receptors for response to occur, slope will be steep.
- -small increase in dose, large increase in effect (NM drugs, inhaled anesthetics)
efficacy or intrinsic activity of dose response curve
- the maximal effect of a drug
- -the plateau on the curve
If you give a complete antagonist what would it do to the drug dose response curve
right shift and decrease maximal response
Test question from last year
- margin of safety
- the difference between the dose of drug that produces desired effect and the one that produces the undesired effect
the ____ the therapeutic index the safer
the range of drug dosages which can treat disease effectively while staying within the safety range
If LD is 100 and ED is 10 what will the TI be?
QUESTION FROM LAST YEARE
If drug has a TI of 1 what does this mean?
QUESTION FROM LAST YEAR
dose will be therapeutic in some and toxic in others. The higher the TI the safeR it is
how does individual variability effect dose response curve
- elderly patients- have decreased cardiac output, enlarged fat content, decreased protein binding and decreased renal function.
- -enzyme activity
- -genetic disorders- variations in metabolic pathways
- -drug interactions- interact to impair absorption, compete with plasma protein binding sites, alter metabolism by enzyme induction or inhibition, change rate of renal excretion.
what is the morst important mechanism by which drugs exert pharmacologic effects
by interaction of a drug with a specific protein molecule in lipid bilayer of cell membranes
what are the 3 excitable transmembrane proteins
- voltage-sensitive ion channels
- ligand gated ion channels
- transmembrane receptors
voltage sensitive ion channels
- open and close in response to changes in voltage across the cell membranes and are represented by classic ion channels such as Na, Cl, K, and Calcium channels.
- -at normal resting membrane potential the channels are closed, when cell becomes depolarized they open
what is the largest subunit of each voltage gated ion channels
ligand gated ion channels
- acetylcholine receptors, serotonin receptors, gamma aminobutyric acid receptors.
- -open and close in response to changes in the presence of extracellular ligands and are involved primarily in fast synaptic transmission between excitable cells.
- a molecule able to bind from a complex with a receptor and produce a response
- -hormones or neurotransmitters that are exogenously administered drugs
- interact selectively with extracellular compounds ( drugs, hormones, neurotransmitters) to initiate a cascade of biochemical changes that lead to the ultimate pharmacologic or physiologic response
- -located in lipid cell membrane
- -This is how water soluble drugs can interact with cell with out penetrating lipid bilayer
transmembrane receptors notify the cell of receptor occupancy by a ligand such as a exogenous drug
what are the 5 receptor familes
- gamma-aminobutyric acid
- guanine nucleotide proteins
gamma aminobutyric acid
- activation of GABA
- -chloride channel receptors that result in hyperpolarization or an increase in ion conductance that prevents depolarization, inhibiting neuronal activity
- closely related to receptors
- -inhibitory receptors that are selectively permeable to anions and mediate rapid inhibitory synaptic transmission (primarily in spinal cord)
- *enhanced by volatile anesthetics
5-hydroxtryptamine receptors (5HT)
- selectively permeable cations
- -exert a variety of effects in CNS
- -glutamic acid does not cross BBB so it must originate from local metabolism
- -activates via metabotropic and ionotropic recptors
guanine nucleotide receptors
- g proteins- intermediaries of intracellular communication that reflects the molecular mechanism of action of multiple drug classes including opioids, sympathomimetics, and anticholinergics
- * 2nd messengers
concentration of receptors in a cell membrane is dynamic they either _______ or _______ in response to stimuli
increase (up regulation) or decrease (down regulation)
- chronic administration of an antagonist results in up regulation as the number and sensitivity of the receptors increase as a response to chronic blockade.
- - patient will develop tolerance requiring higher doses of the antagonist to counteract the increase receptor number
- continued stimulation of cells with agonists generally results in a state of desensitization which is down regulation.
- -effect that follows continued or repeated exposure to the same concentration of drug is diminished.
- -takings increasing doses to get same effects
receptor occupancy theory
- a drug produces its effect by interacting with a specific macromolecule (receptor)
- -true for agonist drugs
state of receptor activation
- States that full agonists convert most receptors from an inactive to activated state,
- partial agonists convert only a fraction of the receptors they occupy, and antagonists don’t activate any receptors they occupy. Increased doses of a partial agonist in the presence of a full agonist will produce a competitive antagonism of the agonist effect
strongest- involved shared electron pairs between atoms.
electrostatic bonds formed by opposites attracting
occur between hydroxyl or amino groups and a negative carboxyl group
van de waals
weak bonds between atoms of two molecules
strength of bonds from strongest to weakest
covalent, ionic, hydrogen, hydrophobic, van der waals
measuring plasma drug concentrations
- measurements at selected intervals are more informative than isolated determination.
- -need to know if measuring free and protein bound drugs, or one or the other
relationship of plasma and receptor drug concentration
- direct relationship between
- -dose of drug administered
- -resulting plasma concentration
- -intensity of drug effect
initial dose of medication
- needed to establish a therapeutic concentration of drug promptly
- -will be larger than maintenance dose
- -changes in VD will influence size of initial dose
when are maintenance doses decreased
with renal or hepatic impairment due to prolonged elimination time
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