Module 3 - Pharmacokinetics and Pharmacodynamics Flashcards
What is pharmacodynamics?
What a drug does to the body
What is involved in pharmacodynamics?
The effect of the drug, mechanism and their action
What is drug selectivity?
The number of molecular targets the drug interacts with
What is drug specificity?
The number of effects the drug produces
What is drug affinity
Affinity = affection
Tendency of a drug to combine with receptor site
What is an adverse reaction?
A biological effect that is not intended
What are the four main types of molecular drug targets?
Transporter
Enzyme
Ion channel
Receptor
What is meant by receptor agonist?
A drug/substance that binds to a receptor and causes the SAME effect
What is a partial agonist?
Unable to produce an active response even when all receptors are occupied?
What is an orthosteric site?
An active site
What is an allosteric site?
Binds to a different site and causes a reaction
What is a receptor antagonist?
Binds to a receptor target but DOES NOT elicit a response
What effect does a receptor agonist produce?
Prevents binding of agonist to receptor thus preventing activation of receptor
What are the three (3) types of receptor antagonists?
Reversible, irreversible and non-competitive
What does a reversible receptor antagonist do?
Interferes with binding of endogenous agonist to orthosteric (active) site
What does a irreversible receptor antagonist do?
Causes target receptor to become permanently unavailable for binding of agonist
What does a non-competitive receptor antagonist do?
Blocks response to agonist
What do allosteric modulators do?
Indirectly alters function of a receptor in positive or negative way
How do allosteric modulators produce a pharmacological response?
Activating receptor to cause different biological response
Alter binding affinity
Changing the efficacy of receptor
What is potency?
How much drug is required to produce an effect
What is EC50?
The drug concentration as which a drug produces 50% of the maximal response
What is efficacy?
Measure of how big an effect the drug will have when all targets are occupied
What are the two types of transporters?
Facilitated and active
When must transporters be utilised?
When a drug is not soluble and cannot passively diffuse across a membrane
What are ion channels?
Transmembrane proteins that control ion flow across a cell membrane
What are the main ion channels?
Voltage gated ion channels and intracellular ligand gated ion channels
What are enzymes?
Catalysts that speed up rate of all chemical reactions that take place with cells
What are receptors?
Signalling proteins that recognise and response to chemical messengers to change a function within a cell
What are the four (4) families of receptors?
- Ligand gated ion channels
- G-coupled protein receptors
- Kinase receptors
- Nuclear receptors
How do ligand gated channels work?
A drug binds to a particular site on the transmembrane protein to open up the gate and allow ions to flow through
How do G-coupled protein receptors work?
A ligand will bind to outside of a G-coupled protein receptor. Receptor undergoes conformational change that allows it to interact with G-protein that will pass signal on to other intermediates in signalling pathway
What is pharmacokinetics?
What the BODY does to the drug
What is involved in pharmacokinetics
- Concentration of a drug increases as it is absorbed in the body
- Hits peak concentration
- Process of elimination occurs (drug concentration in the plasma reduces)
What is the importance of understanding a drugs pharmacokinetic profile?
Allows use to decide appropriate dosages, determine dosing regimes, interpret drug reactions and adjust doses according to response
What are the two main categories of drug administration?
Systemic administration and target administration
What occurs during systemic administration?
Drug enters circulation and is carried to site of action (needs to be able to cross biological membranes)
What occurs during target administration?
Drug is delivered to the site of action (proximity delivered to tissue/organ where desired effect is intended)
What is the difference between lipid soluble drugs and ionised/charged drugs?
Lipid soluble drugs readily pass through lipid membrane, ionised/charged drugs have difficulty crossing cell membranes
What are the four (4) main ways a drug can cross cell membranes?
Passive diffusion
Facilitated transport
Active transport
Aquaporin
What is lipophilicity?
Passes through cell membrane more easily (easier absorption)
What is hydrophilicity?
Difficulty crossing lipid bilayer
What is the impact of ionisation on drug absorption?
Un-ionised drugs (lipid soluble) easily diffuse across lipid membrane compared to ionised drugs
What are the main physiological barriers of drug absorption?
Nature of the tissue
Channel and transporter
Surface area (large surface area increases absorption)
Blood flow (increased blood supply results in increased absorption)
What factors mainly impact distribution?
Physiochemical properties of a drug (e.g. size/molecular weight, lipophilicity/hydrophilicity, ionisation and tissue binding)
Physiology of the person (e.g. circulation, permeability of membranes, tissue mass and channel/transporter)
What is the impact of a hydrophilic drug on distribution?
A large portion will remain in the extracellular fluid compartment as it cannot cross cell membranes
What is the impact of a Lipophilic drug on distribution?
Can move between intracellular and intravascular compartments
