Glossary Flashcards
Define: Placebo
An inactive substance administered as though it is a drug, but which has no therapeutic effect
Define: potency
How much (dose) needs to be administered for a certain response
Define: drug efficacy
How big the maximum response achievable is
Define: drug variability
What proportion of patients will have the desired response
Define: drug selectivity
How selectively the drug acts on its molecular target
Define: drug safety
What proportion of patients will have unwanted side effects (U/E)
Define: drug bio-availability
How much of an administered drug dose enters the blood
Define: Affinity
The extent to which a drug binds to its receptor at a given concentration
Define: Intrinsic activity
The ability of a drug to illicit a pharmacological effect (full agonists have an efficacy of 1, antagonists 0)
Define: S/E
Side effects
Define: U/E
Unwanted effects
Define: A/E
Adverse effects
Define: ADR
Adverse drug reaction
Define: Pharmacovigilance
The detection, assessment understanding and prevention of ADR
Define: Therapeutic window
The range of plasma drug concentrations within which a drug is working therapeutically without side effects
Define and explain: Antagonist
A substance that blocks or reduces the ability of another substance, or agonist, to bind to a receptor and elicit a response.
Antagonists bind to a receptor and prevent agonists from binding to the receptor site. This makes the agonists ineffective.
Define and explain: Competitive (reversible) antagonist
Reversible as antagonists compete with agonist for binding to receptors meaning .. these antagonists can be overcome by increasing dose of agonist
- Directly competes with agonist at ligand binding site (many times per second)
- Reduces potency of agonist
- Maximum response is unchanged
- Effect wears off when drug is cleared by metabolism or excretion (minutes to hours)
Define and explain: Non-competitive (irreversible) antagonist
Irreversibly occupies some of the receptors active sites. The agonist can’t elicit a maximum response from the remaining receptors
These produce an effect that cannot be overcome by increasing agonist dose
* Binds irreversibly to ligand site (or allosterically elsewhere reversibly or irreversibly)
* Reduces potency of agonist as more agonist is required to produce a response
* Maximum response is reduced (fewer available receptors)
Effect wears off when receptor is replaced or recycled (hours to days or weeks)
Some non-competitive antagonists bind elsewhere (irreversibly/reversibly) on the receptor, changing its conformation allosterically so that the agonist cant bind
Define: Pharmacokinetic antagonism
Antagonist reduces concentrations of the agonist in the body by:
* Reducing its absorption or distribution
* Increasing its metabolism or excretion
AKA drug interaction
Define: Partial agonist
Cannot produce a maximal response even when occupying 100% of the receptors. They have low efficacy (intrinsic activity)
Define and explain: Tolerance and Tachyphylaxis
On repeated administration of some drugs, increasing doses need to be given for the same effect as some drugs show declining response on repeated dosing e.g. opioids
* Tachyphylaxis - fast declining response
* Tolerance - slow declining response
May be due to receptor down-regulation, or enhanced drug elimination
