General Principles of Drug Action Flashcards
Intro to Pharmacology
What is pharmacodynamics?
What a drug does to the body
What is pharmacokinetics?
What the body does to a drug (ADME)
What is a drug?
Any single synthetic (or natural) substance of known structure used in the treatment, prevention or diagnosis of disease - can be everyday substances or illicit
What is a medicine?
A chemical preparation containing one, or more, drugs used with the intention of causing a therapeutic effect (usually include additional agents to the active drug)
How can a drug be a useful therapeutic agent?
Must act with a degree of selectivity
What is selectivity?
The ability of a drug to distinguish between different molecular targets in the body
What does selectivity allow drugs to do?
To interact with select cells and tissues to produce their desired effect by binding to particular molecular targets expressed on these cells
How does penicillin work?
Inhibit the enzyme responsible for cell wall synthesis in bacteria (essential for survival) but doesn’t affect the mammalian cell as it doesn’t have the cell wall or enzyme
What types of regulatory proteins do drugs bind to?
Enzymes, carrier proteins (transporters and pumps), ion channels and receptors
Other than proteins what else can a drug’s target be?
RNA and DNA
What are drug receptors?
Protein macromolecules on, or in, cells that mediate the biological actions of hormones, neurotransmitters and other endogenous substances
What is an agonist?
A drug that binds to a receptor to produce a cellular response
What is an antagonist?
A drug that reduces, or blocks, the actions of an agonist by binding to the same receptor
How do agonists activate receptors?
By binding to them temporarily and inducing a reversible conformational change
What is drug affinity?
The magnitude of agonist binding and unbinding (ratio of rate constants) - K+1/K-1
What is drug efficacy?
The ability of a bound agonist to promote a conformational change/activate receptor (alpha/beta)
What changes in affinity?
K-1 (not K+1!!!)
What is drug selectivity dependent on?
The dose (and often the way it is administered)
What side of equilibrium does a high affinity favour?
The product(s)
What side of equilibrium does low efficacy favour?
The reactants
What type of bonds determine affinity?
Chemical - ionic, hydrogen and aromatic (pi-pi)
Why can drug selectivity not be described as specific?
As there is an ‘on target’ (ideal) but there’s also an ‘off target’ (not good news if the drug binds here)
Do antagonists have affinity or efficacy? Why?
Affinity as they DON’T activate anything so can’t have efficacy
When concentration-effect relationship is plotted linearly, what is the effect on the curve?
Hyperbolic
