Lecture 54 - Pharmacokinetics Flashcards
pharmacodynamics
describes the action of the drug in the patient
pharmacokinetics
describes the disposition of drugs in the body
what influences drug dose to plasma concentrations
pharmacokinetic factors
what influences plasma concentrations to pharmacologic response
pharmacodynamic factors
systemic availability
F = fraction of drug absorbed
determined from peak concentration (Cmax) and AUC
clearance
ability of the body or clearance organ to eliminate a drug
CL, CLs = systemic clearance
Elimination
concentration over time
volume of distribution
the volume of body fluid into which a drug distributes
summarize the 5 steps in studying pharmacokinetics
- get subject
- administer drug
- collect serial blood samples
- measure drug concentrations
- plot results
absorption rate
time taken to reach peak concentration (Cmax)
a short half-life drug needs ____ administration
frequent
a long half-life drug needs ____ administration
spaced
what 4 factors affect the volume of distribution
- lipid solubility
- drug pKa and pH of tissues (ionization)
- drug size
- protein binding
T/F: drug diffusion across a plasma membrane depends on its lipophilicity
TRUE
high lipophilicity creates ____ diffusion
more
drug eliminated/dose rate =
drug concentration x clearance
what equation is the rate of delivery
Ca x Q
what equation is the rate of leaving
Cv x Q
what equation is the rate of extraction
Q (Ca - Cv)
what are examples of high-clearance drugs
opiates
fentanyl
beta-blockers
cannabinoids
dexmed
what is the first-pass effect
drugs administered orally will go through detoxification in the liver first and not have the intended effect in target organs
describe hepatic flow limited clearance
dependent on blood flow
CLh = Qh x ERh
describe hepatic clearance when not flow limited
dependent on metabolism
CLh = Cli x fu
*protein free drug
what is a determinant of drug clearance
drug metabolism
