Unit 2: Pharmocokinetics & Pharmacodynamics Flashcards
Define pharmacokinetics.
Pharmacokinetics: study of drug movement throughout the body; describes how the body handles medications
What is the greatest barrier of most medications?
The greatest barrier is crossing membranes that separate drug from its target cell.
Define absorption.
Absorption: process involving the movement of a substance from its site of administration, across body membranes, to circulating fluids. Most drugs must be absorbed to produce an effect.
Describe the permeability of the lipid bilayer.
The lipid bilayer is relatively impermeable to large membranes, ions, and polar molecules and permeable to small, unionized, lipid soluble molecules.
What does degree of ionization depend on?
Degree of ionization depends on surrounding pH.
*Acids are absorbed in acids; bases are absorbed in bases.
What is the purpose of enteric coated drug products?
For oral consumption, drug products may be enteric coated so it will be absorbed in small intestine.
Regular uncoated?
Absorption in stomach.
Buffered?
Contains ions that decrease gastric acidity and slow absorption of acidic drugs.
Define distribution.
Distribution: involves how pharmacological agents are transported throughout the body.
Where in the body gets the most / least blood flow?
Most: heart, liver, kidney, brain
Least: skin, bone, adipose tissues
What are drug-protein complexes?
Drug-protein complexes are drugs that have bound reversibly to plasma proteins and are too large to cross capillary membranes.
What is metabolism / biotransformation and what is the primary site?
Metabolism / biotransformation is the process of chemically converting a drug to a form that is more easily removed by the body. Most metabolism occurs in the liver.
What are Phase I and II metabolism?
Phase I: hydrolysis, oxidation, and reduction in liver
Phase II: addition of side chain conjugates (to make drugs more water soluble and easily excreted by kidneys)
What is the hepatic microsomal enzyme system for?
The hepatic microsomal enzyme system inactivates drugs to accelerate their excretion.
Define prodrug.
A prodrug is a biologically inactive compound that can be metabolized to produce a drug.
What is enzyme induction?
Enzyme induction is the drugs’ ability to increase metabolic activity in the liver.
What are the isoenzymes responsible for the majority of drug metabolism?
CYP3A4: 34%
CYP2C: (subfamily) 25%
CYP2D6: 19%
CYP1A2
What happens if CYP enzymes are induced?
If CYP enzymes are induced, plasma concentrations may fall below minimum effective concentration and higher doses will be needed. Barbiturates induce their own metabolism.
Define loading and maintenance dose.
Loading dose: repeated doses or higher amount of drug given to quickly achieve therapeutic range.
Maintenance dose: given to keep drug in therapeutic range.
What is steady state modelling?
Steady state modelling is the state where drug concentration stays approximately the same (AD=ME).
Define pharmacodynamics.
Pharmacodynamics: refers to how a drug changes the body, concerned with mechanisms of drug action and the relationships between drug concentration and responses in the body.
Define therapeutic window.
Therapeutic window: lies between ED50 and TD50.
Define potency.
Potency: a drug that is more potent will produce a therapeutic effect at a lower dose compared to another drug of the same class.
Define efficacy.
Efficacy: the magnitude of maximal response that can be produced from a particular drug (more important than potency)
Differentiate between agonist and antagonist.
Agonist: produces the same type of response as an endogenous substance.
Antagonist: will occupy receptor and prevent endogenous chemicals from acting.
Agonists have affinity and efficacy; antagonists only have affinity.
What is an inhibitor?
Inhibitors bind to sites on other proteins that stop activity of that protein.
In relation to pharmacodynamics, what four things do proteins do?
1) receptor
2) enzymes
3) tranport
4) ion channels
