Pharmacokinetics & pharmacodynamics Flashcards
Km=
1/affinity
Vmax is ______ proportional to _____?
directly, enzyme concentration
Lineweaver burk plot: the closer the line is to X axis:___?
The higher the Km (lower the affinity)
What is the bioavailability for IV dose
F=100%
What is the bioavailability for an oral dose
F
Volume of distribution=
amount of drug in body/plasma drug concentration
High volume of distribution
All tissues (including fat) Small lipophilic molecules, esp if bound to tissue protein
Medium volume of distribution
ECF
Small hydrophilic molecules
Low volume of distribution
Blood
Large/charged molecules, plasma protein bound
Clearance=
rate of elimination of drug/plasma drug concentration
=Volume of distribution*elimination constant
How many half lives does it take to reach steady state?
4-5 half lives
How many half lives does it take to reach 90% of the steady-state level?
3.3
T1/2=
(.693*Vol. of distribution)/Clearance
Loading dose=
(Target plasma concentration at steady state*Vol.ofDis)/Bioavailability
Maintenance dose=
(Target plasma concentration at steady stateClearancedosage internal)/bioavailability
Do you change loading dose or maintenance dose with kidney/liver disease?
Decrease maintenance dose
loading dose is unchanged
Drugs that are zero order elimination
PEA: Phenytoin, ethanol, aspirin
What state do you want a drug to be to “trap” it in the urine?
Ionized state (can’t be reabsorbed)
Example of a weak base
Amphetamines
Example of a weak acid
Phenobarbital, methotrexate, aspirin, TCAs
How do you treat a weak acid overdose?
Bicarbonate
How do you treat a weak base overdose?
Ammonium chloride
Phase 1 of metabolism
Reduction and oxidation
p450
Phase 2 of metabolism
Conjugation: glucuronidation, acetylation, sulfation
How does the speed of conjugation (phase 2) affect side effects?
The fast the conjugation, the less the side effects
Geriatric patients lose which drug metabolism phase first?
Phase I
Diazepam+Flumazenil: Receptor types, and effect when combined
Diazepam (GABA agonist) + Flumazenil (GABA competitive antagonist
Flumazenil decreases potency
NE+ phenoxybenzamine: Receptor types, and effect when combined
NE (a agonist) + phenoxybenzamine (a nonceompetitive antagonist)
Phenoxybenzame decreases efficacy
Morphine + buprenorphine
Morphine (u agonist) + Buprenorphine (u partial agonist)
Buprenorphine decreases efficacy, potency is independent
