Receptors, agonists and antagonists
What the drug does to the body: binding to a receptor, agonists, partial agonists and antagonists, affinity, efficacy and potency, the therapeutic index, the main adrenergic and muscarinic receptors, tolerance, and the antagonists used as antidotes.
- 36 cards
- 3 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- Scenarios
- Understand
A few cards from the deck
Agonist: what is it?
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A drug that binds a receptor and activates it, as the natural substance would.
Morphine is an agonist of opioid receptors.
An unconscious young man has pinpoint pupils and breathes 6 times a minute. What is injected?
- Naloxone, an opioid antagonist
- Morphine
- Adrenaline
- Insulin
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Naloxone, an opioid antagonist
It drives the opioid off its receptors and restarts breathing.
Antagonist: what is it?
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A drug that binds a receptor without activating it and stops the agonist acting.
Competitive antagonist: a larger agonist dose can displace it.
Why can a high agonist dose overcome a competitive antagonist?
- The antagonist destroys itself
- The agonist changes receptor
- It is impossible
- Both compete for the same site: more agonist occupies more receptors
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Both compete for the same site: more agonist occupies more receptors
The dose-response curve shifts right without losing its maximum.
Partial agonist: what is it?
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A drug that activates the receptor but cannot reach a full agonist's maximal effect.
Buprenorphine is an example: its effect has a ceiling.
Salbutamol relieves an asthma attack. How does it work?
- It is a beta-1 antagonist
- It is a beta-2 agonist that widens the airways
- It is a heart muscarinic antagonist
- It is a corticosteroid
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It is a beta-2 agonist that widens the airways
Its residual beta-1 effect can speed up the heart.