Pharmacology 2 - Drug Receptor Interactions Flashcards
Define drug
A chemical substance that interacts with a biological system to produce a physiological effect.
List the types of drug target sites
- Receptors
- Ion channels
- Transport systems
- Enzymes
- All sites are PROTEINS
Define agonist and antagonist and give examples
- An agonist/ligand is something that stimulates a receptor (nicotine and ACh)
- An antagonist is something blocks a receptor (atropine and hexamethonium)
Give examples of drugs that act on receptors
- Acetylcholine (agonist)
- Atropine (antagonist - muscarinic)
List the two types of ion channels
- Voltage sensitive (eg. VSCC)
- Receptor linked (eg. nicotinic ACh receptor)
Give examples of drugs that act on ion channels
- Local anaesthetics (block voltage sensitive sodium channels)
- Calcium channel blockers (-dipine)
Give examples of drugs that act on transport systems (against conc. gradients)
- Tricyclic anti-depressants (TCAs) - treat clinical depression
- Cardiac glycosides
List the possible drug interactions of enzymes and give examples of a drug that performs each interaction
- Enzyme inhibitors (eg. anticholinesterases like neostigmine)
- False substrates (eg. Methyldopa which causes methyl-noradrenaline production rather than noradrenaline, reducing blood pressure)
- Prodrugs (eg. chloral hydrate to trichloroethanol)
Give examples of non-specific drugs
- Antacids
- Osmotic purgatives (laxatives)
What does potency of a drug depend on?
- Affinity (avidity of which the drug binds to the receptors)
- Efficacy (intrinsic activity, where a response is generated upon binding)
Compare full and partial agonists
- Full agonists generate maximal response
- Partial agonists cannot generate maximum response (they have some antagonist activity against full agonists)
List the main qualities of antagonists
- Affinity but no efficacy (they just block receptors)
- May be competitive or irreversible
Describe competitive antagonists and give some examples
- Same site as agonist
- Surmountable (if you increase agonist conc, it can be overruled)
- Shifts the D-R curve right (max can be reached)
- eg. Atropine/propranolol
Describe irreversible antagonists and give an example
- Binds tightly or at different site
- Insurmountable (binds too strongly to be overruled, max cannot be achieved)
- eg. hexamethonium
Define potency
The powerfulness of the drug
Define pharmacodynamics
The effect of the drug on the body
Define pharmacokinetics
The effect of the body on the drug and the metabolism of the drug
How does paracetemol overdose harm the liver and kidney?
- The paracetemol overcomes the number of enzymes, and instead reacts with a different enzyme producing harmful intermediates
- An antidote is then required
How can inactive drugs be stored in the body?
Bound to albumin (plasma protein binding), acts as a reservoir
Compare selectivity and specificity
- Specificity is only binding to one specific receptor
- Drugs show selectivity - preferably bind to one receptor but can also bind to different receptors in high concentrations
Why is structure important in drugs?
- Lock and key mechanism
- Small changes in agonists can create antagonists and alter pharmacokinetics
Compare the logarithmic dose response curve of full and partial agonists
- Full agonists are towards the left, and very steep
- Full agonists with a lower affinity are to the right hand side with the same gradient
- Partial agonists have a smaller gradient and lower max response
Compare the logarithmic dose response curve of competitive and irreversible antagonists
- Competitive antagonists are shifted right compared with agonists alone, as a higher concentration is needed for the same response. Max response is still reached
- Irreversible antagonists have a smaller gradient and do not reach max, they are also shifted much further right
