W5 Receptor And The Effect Of Drugs Flashcards
Why are drugs isolated to be the active ingredient?
- to avoid harmful effects on non-active ingredients
- to standardise dosing
- to allow for the development of better medicines through chemical modification of lead compounds
- to allow for industrial scale synthesis
What does the small size of a drug influence?
- more likely to be soluble
- more likely to be absorbed from the gut
Names of drugs
- a chemical name - systematic name
- a generic name - internationally agreed by WHO
- a brand name - marketed by pharmaceutical companies
What is an agonist?
A chemical that binds to its target to increase activity
What is an antagonist?
A chemical that opposes the action of another chemical. This means antagonists should have no action on their targets in the absence of an agonist,
Is it common for an endogenous agonist (e.g., a hormone) to be continuously present in the body?
Yes, so antagonists will cause physiological effects by themselves.
Measuring the effect of a drug
The EC’50 is the molar concentration of an agonist that produces 50% of the maximal possible effect of that agonist.
Relationship between dysfunction and receptor binding of a drug
Dysfunction is proportional to the probability of a receptor being bound by a drug as the drug concentration changes.
Are most antagonists competitive or non-competitive?
Most are competitive
What is a competitive antagonist?
The binding of the antagonist prevents the binding of the agonist by competing for the same binding site.
What is the concentration ratio?
The ratio of the concentration of an agonist that produces a specified response in the presence of an antagonist, to the agonist concentration that produces the same response in the absence of antagonist. When giving a fixed amount of a drug, then the term Dose Ratio (DR) is used.
What is a non-competitive antagonist?
Binds at a different binding site from the antagonist, and prevents the effect of the agonist without preventing its binding. Effect is insurmountable (cannot be overcome by adding more agonist).
What is efficacy?
A measure of the degree to which an agonist produces a response when binding a given proportion of receptors. For a full agonist, the efficacy is 1. For a partial agonist, the efficacy is less that 1 (but greater than 0). In some cases it is possible to have a negative efficacy in which case the drug is called an inverse agonist. Such drugs inhibit any intrinsic activity of a receptor that might exist in the absence of any ligand.
What does a competitive antagonist do to the typical agonist and binding curve?
This gives a right shift in the relationship between agonist concentration and binding.
Effect of competitive antagonists on the EC50 of the agonist
The competitive antagonist will increase the apparent EC50 for the agonist. It’s effect can be overcome by adding a sufficiently high concentration of the agonist.
