Pharm Kinetics & Dynamics PowerPoint Flashcards
In general, pharmacokinetics are?
What the body does to a drug once administered
In general, pharmacodynamics are?
What a drug does to the body
Would you need a bigger or smaller dose if a drug has a high bioavailability?
Smaller. More available, don’t need to give as much.
What system is essential for delivery of drugs to various tissues
vascular system
Do bound or unbound drugs enter organs, muscles, fats and bind to receptors
Unbound. Cannot bind to receptors or pass through membranes when bound to albumin
If drugs are highly protein-bound, would you need a higher or lower dose?
Higher dose. Less free drug is available when bound.
What are nondrug properties that influence uptake?
Amt of blood flow to tissue
Concentration gradient of drug across membrane.
When pH = pKa of a drug, how is drug ionization affected?
ph = pka of a drug:
50% ionized
50% nonionized form
When a drug is in its ionized form, what is its solubility and ability to cross membranes
Water Soluble (polar)
Unable to easily penetrate lipid cell membranes
When a drug is in nonionized form, what is its solubility and ability to cross membranes?
Lipid Soluble (nonpolar)
Diffuses across cell membranes easily. Like Blood-brain barrier, gastric cells, placental barriers
How does pKa relate to acid base dissociation?
Pka is the negative log of the equilibrium constant of the acid or base. The pH at which the drug is 50:50 ionization
What is the most abundant plasma protein
albumin
High protein binding results in what kind of plasma concentrations?
High plasma concentration. Low tissue/target receptor concentrations
The number of protein binding sites for a drug is finite. How can we “overcome” this?
By adding more drug, we can surpass the amount of protein binding sites available and force drug out of plasma and across membranes
Receptors have what three common properties?
Sensitivity
Selectivity
Specificity
What are the 5 types of bonds drugs and receptors form?
van der Waals
Hydrophobic
Hydrogen
Ionic
Covalent
Do drug receptors need to be completely saturated to elicit effect?
No. Complete saturation of available receptors with drug is not necessary for a desired tissue response. This is due to sensitivity.
What is affinity
Degree of attraction b/t a drug and its receptor on the cell’s surface
What is efficacy
a drugs capacity to produce an effect
How are compartment models useful?
Useful for predicting serum concentrations and changes in drug concentrations in other tissues
The single-compartment model is NOT sufficient to describe many drugs, including?
Lipid-soluble anesthetic drugs. Such as propofol.
What is the equation for volume of distribution
Vd= dose of drug / plasma concentration
What is the effect of enzyme induction?
Increase in enzymes.
System can break down more agent that uses the same enzymatic system for biotransformation
-leads to reduced half-lives
Describe First-Order Kinetics
Drug is cleared at a rate proportional to the amount of drug present in the plasma.
-Always a proportional rate, a percentage.
-Negative exponential curve
Do most drugs follow First or Zero order Kinetics
First Order
Describe Zero Order Kinetics
Is an Amount. (not a proportion or percent)
A constant amount of drug is cleared regardless of plasma concentration.
-Negative Liner Curve
Matabolism occurs in two phases. Do all drugs go through phase 1 and then phase 2?
No. Many drugs already possess an appropriate functional group for conjugation and do not need to be modified by a prior phase 1 rxn to be conjugated.
Drug is regarded as fully eliminated when ~95% has been eliminated. This usually occurs when?
~4-5 half lives
What is clearance?
The volume of plasma completely cleared of drug by metabolism and excreted per unit of time
Clearance is directly and inversely related to?
Directly: The dose
Indirectly: The agent half-life and concentration in the central compartment
