Lecture 6.1 & 6.2: Drugs and Receptors Flashcards
How do (most) drugs exert effects?
By binding specifically to a TARGET
What is EC50?
Effective concentration giving 50% of the maximal
response
Relevance of altered receptor number
- Receptor numbers are not fixed:
- Tend to increase with low activity (up-regulation)
- Tend to decrease with high activity (down-regulation)
- Physiological, pathological or drug-induced changes
for drugs
Risks of Opiods
- Addiction
- Respiratory depression – can lead to death
What does Efficacy mean in pharmacology?
The capacity of a drug to produce an effect
What does Efficacy mean in colloquial terms?
It is often used clinically to describe how good a drug is at producing a response
How do Antagonists work?
Block the effects of agonists ie. prevent receptor activation by agonists
What are the types of Antagonism?
1) Reversible competitive antagonism (commonest and
most important in therapeutics)
2) Irreversible competitive antagonism
3) Non-competitive antagonism (generally allosteric or
even post-receptor)
What is Naloxone?
Naloxone is a high affinity, competitive antagonist
at μ-opioid receptors
Why might Naloxone be useful clinically?
Reversal of opioid-mediated respiratory depression
- high affinity means it will compete effectively with
other opioids (e.g. heroin) for receptors
What drug is used in hypertension episodes in phaechromocytoma?
Irreversible competitive antagonists e.g. phenoxybenzamine – nonselective irreversible a
1-adrenoceptor blocker
What is an Agonist?
An agonist is a chemical that activates a receptor to produce a biological response
What is the spare receptor hypothesis?
- A certain number of receptors are “spare.”
- Spare receptors are receptors that exist in excess of
those required to produce a full effect
What is Potency?
It is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity
Types of Agonists (2)
- Partial agonist
- Inverse agonist
