ICPP - Pharmacodynamics Flashcards
Give some examples of drug targets (RITE)
- Receptors
- Ion Channels
- Transporters
- Enzymes
How is molarity calculated?
Molarity = g/L divided by Mr (molecular weight)
Put these in order from largest to smallest:
Nanomolar, millimolar, picomolar, micromolar, molar
Molar, millimolar, micromolar, nanomolar, picomolar
Why are drug concentrations measured in molarity rather than mg/L?
They may have a different molecular weight, so they could have the same conc in mg/L but a larger number of molecules (which determines drug action).
What is a ligand?
Molecule (or ion) that binds specifically to a receptor
What does an antagonist do?
Blocks the binding of an endogenous agonist
What is the difference between affinity and intrinsic efficacy?
Affinity governs whether something will bind to a receptor, while intrinsic efficacy governs whether it will activate the receptor.
Define efficacy
The ability of a ligand to cause a response
Do agonists and antagonists have efficacy and intrinsic efficacy?
Agonists have intrinsic efficacy and efficacy. Antagonists have affinity only, meaning they cannot cause a response after binding to the receptor.
How are drug-receptor interactions measured?
Often by binding of radioactively labelled ligand (radioligand) to cells/membranes. Low [ligand] = low binding, high [ligand] = high binding
What is Bmax?
Like Vmax, the maximum binding capacity
What is Kd?
The concentration of ligand required to occupy 50% of the available receptors. It is an index of affinity, so low value = high affinity.
How is Kd obtained usually?
Radioligand binding, although it can also be determined by other means and is then known as KA.
Why are graphs showing proportion of bound receptors against [drug] usually sigmoidal?
Because conc of drug is so small that it is done with a logarithm, like pH.
What is the EC50?
Effective Concentration giving 50% of the maximal response. Note - on graphs where [drug] is a log, remember that the EC50 when read off the graph will also be a log.
