PK/PD Flashcards
Just try not to soil yourself. Then we all look bad...
Down and dirty: What is pharmacodynamics?
How a drug affects the body.
Down and dirty: What is pharmacokinetics?
How the body affects a drug.
4 aspects of PK?
ADME: A- absorption D- distribution M- Metabolism (or biotransformation, don't let that term trick you up) E- Excretion (or elimination)
What the heck does ‘chiral’ mean?
Describes the possibility of stereoisomerism/ enantiomerism in a molecule; also describes the carbon atom around which such isomerism may exist.Also, you can think of it as a Carbon with 3 or 4 different elements attached to it.
What is an enantiomer?
A molecule that exhibits chirality; enantiomers of each other have the same chemical makeup, but on a carbon, things are arranged differently such that two enantiomers are mirror images of each other without being able to be superimposed on each other (right hand and left hand)
Similarities between enantiomers?
Same physical properties: molecular weight, boiling/freezing points, etc. Similar chemical properties: combustion, etc.
Enantiomers are either _____- or _____-rotatory.
levo- dextro- (remember that this has to do with their ability to polarize and rotate light when dissolved in a solution)
How do enantiomers differ?
Absorption, distribution, clearance, potency, and toxicity.
What does racemic mean?
Combo of levo and dextrorotatory forms of molecules
Common racemic drugs?
Racemic epi fluoxetine warfarin ibuprofen omeprazole atenolol atropine thiopental ketamine NMBs Local anesthetics Opioids
Define: hyperactive
Describes person in whom an expected effect is achieved with a lower-than-normal dose
Define: hypoactive
Describes a person in whom a higher-than-normal dose is required to achieve an expected effect
Define: tolerance
When an increasing dose is required to achieve the same effect. If this happens rapidly, it is known as tachyphylaxis.
Define: idiosyncrasy
unexpected unusual effect
Define: additive effect
drugs added together achieve a larger effect (1+1=2)
Define: synergistic effect
drugs added together achieve a much larger result (1+1=384)
Define: ligand
molecule that interacts with or bonds to a receptor
Define: antagonism
the binding of a chemical to a receptor in such a way that no effect is produced
Define: agonism
a chemical binds to a receptor and elicits a response from said receptor
Define: competitive antagonism
increasing concentrations of antagonists progressively inhibit the response to an unchanging concentration of an agonist
Define: noncompetitive antagonsim
when even at high doses, an agonist cannot overcome antagonism
What is bioavailability?
The amount of active drug that remains in circulation after first-pass metabolism
What is volume of distribution (Vd)?
A number that expresses how much of a drug is distributed out of the circulation; the larger the number, the more extensive the distribution is.
What is clearance?
The amount of plasma that is cleared of a drug.
- Hepatic
- Biliary
- Renal
First-order kinetics. What is that?
A constant FRACTION is cleared in a given time
Zero-order kinetics. What do that be?
A constant AMOUNT is cleared in a given time
Elimination half-time v. context-sensitive half-time
Elim T1/2: time needed for [plasma] of drug to decrease by 50% during elim. phase
CS T1/2: time needed for [plasma] to decr by 50% after d/c continuous infusion
Number of elimination half-times needed to clear a drug?
~5 half-times:
T1/2 Fraction remains % cleared
0 1 0
1 1/2 50
2 1/4 75
3 1/8 87.5
4 1/16 93.8
5 1/32 96.9
6 1/64 98.4
Think about a two-compartment model… What is the first (central) compartment?
Vasculature, vessel-rich organs (brain, lungs, heart, kidneys, liver)
Think about that two compartment model again… What is the second (peripheral) compartment?
Collectively the fat, muscle, and vessel-poor groups.
Factors affecting distribution between compartments…
Age (higher [plasma])
Residual drug
Lipid solubility of drug
Elimination rate
