Pharmodynamics and kinetics Flashcards
____ refers to how effective a drug is at producing a response
Efficacy
drugs with a ____ first pass effect have ____ bioavailability
high, low
what is the primary site of drug elimination
the kidney
Rate of renal excretion = ?
filtration + secretion - reabsorption
When does steady state occur?
occurs after multiple drug doses when the average drug concentration no longer changes, i.e. when the amount of drug going into the body is equivalent to the amount of drug leaving the body over the dosing interval. Approximate by multiplying half-life by 5.
Which phase of drug metabolism is enzymatic, which increases water solubility via conjugation and deactivates active metabolites?
phase 2
What is pharmacokinetics
what the body does to the drug
Describe phase 2 of drug metabolism
enzymatic, increases water solubility via conjugation and deactivates active metabolites
What is the primary site of drug metabolism
the liver
which are more easily absorbed: hydrophilic or lipophilic drugs
lipophilic
When environmental pH is lower than the drug pH, more of the ______ form predominates
un-ionized, protonated
un-ionized drugs are more ____ soluble, and therefore cross cell membranes ____
lipid soluble, cross cell membranes readily
What is bioavailability
the percentage of a drug dose that reaches systemic circulation
The magnitude and percent of clinical response is called
clinical efficacy
What is Tmax
the time at which the drug reaches Cmax, the highest measured concentraion in the plasma
What is the consequence of a drug being protein bound?
it cannot be filtered through the glomerulus, and it is not typically bioavailable.
What is the most important transport protein that moves drugs out of cells
P-glycoprotein
What is ion-trapping
a phenomenon where the drug will accumulate more in the compartment where it is more ionized (aka the compartment that has a pH further from the drug’s pKa)
Lipophilic drugs go into ____, hydrophilic drugs go into ____
fat, fluid compartmetns
What is the Area under the time concentration curve (AUC) a measure of?
the animals total exposure to the drug
If the environmental pH is higher than the drug pKA, the ____ form predominates
ionized (deprotonated) form
Which of the four processes of pharmacokinetics is not applicable to IV administration?
Absorption, as it is immediately at Cmax in the blood
What is Cmax and what does it determine?
the highest concentration achieved by the drug in the plasma. This is determined by bioavailability and relative rate of absorption, distribution, metabolism/elimination
Rank the drug receptors from fastest to slowest
ligand gated
g-protein coupled
enzyme receptors
intracellular receptors
What is the first phase of drug metabolism, and what happens
Redox reactions, carried out by cytochrome P450
What are the phases of drug metabolism
redox
Enzymatic
What two things does metabolism increase in a drug
polarity and water solubility
what type of administration can over-come the first pass effect
rectal
equation for loading dose
loading dose= Vd x desired drug concentration
what is pharmacological efficacy
the inhibition or activation of receptor activity
what is potency
the concentraiton of a drug required to produce a response
speed of absorption depends on ____
blood flow. This is why IM injections are more readily absborbed than SQ
What is Vd?
The theoretical volume that would be needed to contain the total amount of administered drug at the initial concentration (C0) in the plasma after IV administration (or at Cmax after other forms of administration. Higher Vd means more distribution of the drug from the blood into the tissues, but not specific sites
What does a higher Vd indicate?
more distribution of the drug from the blood into the tissues
What is the clearance (Cl) of a drug after a single dose equal to?
dose/AUC
What is a half life
the length of time it takes for the concentration of the drug in plasma to decrease by half (t1/2). When the dose is doubled, the duration of drug action is extended by 1 halflife
What are the four physiological responses associated with pharmacokinetics
absorption
distribution
metabolism
elimination
