Pharmacokinetics Flashcards
Pharmacokinetics vs pharmacodynamics
kinetics = what body does to drug
dynamics = what drug does to body
most oral drug absorption occurs in the…
small intestine, after gut absorption enters portal vein and travels to liver
First pass metabolism is when….
drug extensively metabolized in liver before reaching systemic circulation
Drug absorption, fastest to slowest
IV -> SL -> ODT -> immediate-release tablets -> extended release tablet
Enteric coated drug formulations will…
limit drug degradation in the stomach
If drug has poor absorption, can increase dissolution rate by…
reduce particle diameter which will increase surface area
Poorly soluble drugs are generally…
lipophilic = lipid loving
poor systemic absorption
Freely soluble drugs are generally…
hydrophilic = water loving
good systemic absorption
Bioavailability is….
extent of drug absorption into systemic circulation
How to calculate bioavailability….
area under the plasma concentration time curve (AUC)
factors that impact drug distribution include….
drug lipophilicity
molecular weight
solubility
ionization
protein binding
Factors that favor greater drug distribution include….
high lipophilicity
low molecular weight
unionized status
low protein binding
Primary sites for drug metabolism
gut and liver
Phase I metabolism reactions
oxidation
reduction
hydrolysis
Phase II metabolism reactions
Conjugation
How to increase renal exertion by adjusting urine acidity
for weak base = acidify the urine
for weak acid = alkalinize the urine
First order elimination is when…
constant percentage of drug is eliminated per unit of time
ie 20% of the dose
Zero order elimination is when….
constant amount of drug is removed per unit of time
ie 20mg no matter the dose
Michaelis-Menten kinetics is when….
saturable kinetics
have a max elimination based on drug concentration
drugs that exhibit Michaelis-Menten kinetics….
Phenytoin
theophylline
voriconazole
Elimination rate constant equation
Cl/ Vd
Half life equiation
0.693/ ke
How many half lives to reach steady state
usually about 5
How many half lives to eliminate 95% of a drug
5
Peak and trough levels for therapeutic drug monitoring
Peak is 30min after infusion is finished
Trough is right before or 30min before next dose given
