Intro to Pharmacokinetics Flashcards
(22 cards)
ADME
Absorption
Distribution
Metabolism
Elimination
Pharmacodynamics
how the drugs affect the body
Pharmacokinetics
how the body affects/handles the drug
Pharmacokinetic calculations needed for…
- concentration dependent efficacy/toxicity
2. Narrow therapeutic index
Absorption
Passive
- ionized (eliminated) v. unionized (re/absorbed)
Active absorption/transport (and carrier mediated)
1. ENERGY REQUIRING
2. Saturable - competitive inhibition by other meds
3. Movement against gradients - electrochemical and concentration gradients
Lipid solubility in ionized v. unionized
Ionized - Lower lipid solubility = do not easily diffuse across lipid bi-layer membranes
Unionized - higher lipid solubility = easily diffuse across lipid bi-layer membranes
Ionization status depends on 2 factors
- pKa of med
- pH of membrane gradient
When pKa=pH; 50:50 ratio of ionized:unionized
2 body systems where pH varies and commonly impacts ionization status
GI tract
Kidneys
Protein binding: bound v. unbound
bound = inactive UNBOUND = ACTIVE
alpha (small v. large)
unbound fraction
small alpha = less unbound
Phase 1 Reaction
Metabolism - alters functional groups (oxidation, reduction, hydrolysis)
Phase 2 Reaction
Metabolism - alters covalent linkages (glucuronidation, sulfation, acetylation)
Cytochrome P450 Enzyme System
Main sites: liver, GI, Brain, Kidney
CYP450 enzyme inducers
carbamazepine
phenytoin
phenobarbital
isoniazid
CYP450 enzyme inhibitors
fluoxetine
omeprazole
cimetidine
First pass metabolism
determines oral administration v. IV
liver metabolizes
Elimination via liver and kidneys:
lungs, sweat, bile/feces
REduced renal or hepatic function may result in ____ in dose
change
3 main processes of Renal Elimination
- Passive GF
- Passive tubular diffusion
- Active tubular secretion
Passive GF
blood flow dependent
Passive tubular diffusion
PcT, DcT
ionization and concentraiton status dependent
Active Tubular secretion
weak acids/bases secreted into PcT
