Drug Receptor Interactions Flashcards
(43 cards)
What is Pharmacokinetics?
The effect of the body on the drug (e.g. absorption, distribution, metabolism, excretion)
What is Pharmacodynamics?
The effect of the drug on the body (responses produced, mechanism of action)
What is a Drug?
“a chemical substance that interacts with a biological system to produce a physiological effect”
Name 4 drug target sites:
- Receptors
- Ion channels
- Transport systems
- Enzymes
- All proteins
Where are receptors found?
Normally proteins within cell membranes.
Can be steroids in nucleus
How are receptors activated?
By Neurotransmitters or endogenous hormones
How can a receptor be defined?
By responding to different agonists and antagonists
Give 1 example of a Receptor Agonist and Agonist:
ACh - Agonist
Atropine - Antagonist
What is Atropine?
Muscarinic cholinoceptor antagonist used as anaesthetic premedication to dry up secretions
Name the 2 types of Ion channels:
Voltage-sensitive e.g. VSCC
Receptor-linked e.g. nAChR (Nicotinic ACh Receptor)
Give an example of a drug which effects Ion channels:
Calcium channel blockers (dipines)
Local anaesthetics (Sodium channels)
How does Lidocaine work?
(And other local anaesthetics)
Work by blocking voltage-gated sodium channels in the sensory axons
Blocking these channels in sensory axons means that fewer action potentials are propagated along those axons and so the perception of pain is reduced
What is the difference between a Transport system and a Receptor?
They don’t mediate a response, all they do is allow the NT to bind to a protein and then move it somewhere else
What are Transport systems?
Systems of carriers that transport substances against their concentration gradient e.g. glucose ions, neurotransmitters
Give two examples of Transport systems:
Na+/K+ pump
Noradrenaline uptake 1
Give two examples of classes of Transport system drugs:
Tricyclic antidepressants (TCAs) Cardiac Glycosides
Give an example of a cardiac glycoside:
What does it do?
Digoxin
Interacts with Na+/K+ pump
Which Transport system antagonist would you give a patient with heart failure, and how does it work?
Digoxin
- It will slow down their Na+/K+ pump and that has a knock-on effect that INCREASES the intracellular calcium concentration
- This, in turn, increases the force of contraction
- So, overall, digoxin increases the contractility of the heart
What are the three ways a drug can interact with Enzymes?
By being:
Enzyme Inhibitors
False Substrates
Prodrugs
What are Enzyme inhibitors and give an example of one:
E.g. anticholinesterases - increases the concentration of acetylcholine in the synapse by decreasing the rate of breakdown of acetylcholine.
Neostigmine
What antihypertensive drug is a False Substrate, and how does it work?
Methyldopa
It takes the place of DOPA in the NA production pathway, reducing the amount of NA produced, making Methylnoradrenaline instead.
MethylNA is worse at vasoconstriction, so hypertension is reduced.
What is a prodrug, and give an example of how it interacts with enzymes:
Chloral hydrate - insomnia - chloral hydrate needs to go to the liver and be metabolised into trichloroethanol before it is effective so technically chloral hydrate must interact with an enzyme system before it becomes useful
What can unwanted effects of drugs on enzymes be using Paracetamol as an example?
Paracetamol - if you take an overdose then you saturate the liver’s microsomal enzymes so another set of enzymes (P450) starts breaking down the paracetamol and the metabolites interact with the liver and kidneys
What are three types of drugs that don’t fit the 4 target site model?
General Anaesthetics
Osmotic Purgatives
Antacids
