7. Pharmacokinetics Flashcards
What is the most common membrane transport mechanism for absorption?
Simple diffusion (direct penetration)
When can a drug cross the membrane?
when it is nonpolar
What is where exactly one half of weak acid is ionized?
pKa
Lower pH means more H+ increases likelihood that a parent molecule has?
an H+ attached
When you are a weak acid, you would be more readily absorbed in the stomach. Why would a weak acid become trapped in basic compartments?
Negative charge (acid) needs H+ so they are unionized so they are able to cross memebranes, but in a basic environment, no H+ to give
Amount absorbed = S* F* Dose
Ka = rate constant for absorption s= salt factor (less than 1) F= bioavailability (fraction that reaches bloodstream less than 1)
F is bioavailbilty is equal to Area under curve AUCoral/ AUC IV. F equalling what?
the oral dose that enters the plasma (bioavaiblility)
Ionized or polar drugs can only cross capillaries for distribution between, while lipid soluble drugs can?
cross through the bed
When a drug is bound to albumin in the blood, is it considered free?
NO! it is only bioactive if free from binding proteins
When in the brain what cannot cross the BBB unless they have a transporter?
Ionized or polar drugs (lipid soluble can still pass)
what is the equation for concentration in plasma Cp
S * F * Dose / Vd
Vd= Volume distribution = Amount drug in body/ [plasma]
The major site of drug metabolism is in?
the liver
Phase 1 of metabolism or biotransformation involves oxidation, reduction and hydrolysis to form a more polar drug, What is phase 2?
conjugation occurs via glucuronidation and sulfation and acetylation/methylation to increase molecular weight
What are the 3 steps in renal drug excretion?
glomerular filtration (small drugs) passive tubular reabsorption (lipid soluble/unionized) active tubular secretion (protein bound drugs)
What is a dose needed to rapidly acheive therapeutic drug concentrations for drugs with a very long 1/2 life (digoxin)?
loading dose
