ICS pharmacology Flashcards
What is pharmacology?
The study of the effects of drugs
What is pharmokinetics?
- How the body affects the drug:
- Absorbtion,
- Distribution,
- Metabolism
- Excretion
ADME
What is pharmacodynamics?
How the drug affects the body
What is the main target for drugs?
Receptors
What are 3 things that naturally target receptors?
- Neurotransmitters e.g., acetylcholine, serotonin
- Autoacids (local hormones) e.g., cytokines, histamine
- Hormones e.g., testosterone hydrocortisone
What are the different types of receptors?
- Ligand-gated ion channels
- G protein coupled receptors (most common)
- Kinase-linked receptors
- Cytosolic/nuclear receptors
Name some drug targets that aren’t receptors?
- Enzymes
- Transporters
- Ion channels
Most drug targets are proteins
What receptors do ligand-gated ion channels have?
Nicotinic ACh receptors
What receptors do G protein coupled receptors have?
- M3R (muscarinic receptor)
- Beta-2-adrenorecepto. Produces second messenger cyclic-AMP
What are kinase-linked receptors targets for?
Growth factors
What are cytosolic receptors targets for?
Steroids
What disease is the loss of nicotinic ACh receptors implicated in?
Myasthenia gravis
Define potency?
Measure of how well a drug works
What is a drug agonist?
A compound that binds to a receptor and ACTIVATES IT
What is intrinsic activity?
- Emax of partial agonist/Emax of full agonist
- Basically, how well a drug works against something that fully works
What is the difference between potency and efficacy?
- Potency is which drug is more effective at the same concentration
- Efficacy is with unlimited concentration which drug will be more effective
What is an antagonist?
A compound that reduces the effect of an agonist
How do competitive antagonism work?
- The reverse the effects of agonists by competing with them to bind with receptors.
- This therefore prevents agonists from having as strong of an effect
- They shift the curve to the right meaning more agonist is required for the same response
How does non-competitive antagonism work?
- It binds to a receptor and prevents activation of the receptor. The same amount of agonist can still bind it will just be less effective
- It shifts the curve right and down meaning even more agonist is required to illicit the same response
What is affinity?
How well a ligand/drug binds to the receptor
- Property shown by both agonists and antagonists
What is efficacy?
Describes how well a ligand/drug activates the receptor
- Only agonists show efficacy
What is allosteric modulation?
- Binding of an allosteric ligand to a receptor can affect an agonists effect
- Can change affinity and efficacy
- Can be positive or negative
What is tolerance?
- The reduction in drug effect over time
- Seen with continuous, repeated high concentration of drug over time
How does tolerance occur?
- Receptor can’t interact with G-protein
- Receptor becomes internalised in vesicle of the cell
- Receptor becomes degraded
Why is selectivity used to describe drug targeting than specificity?
Because no compound is truly specific
Give an example of a drug that is highly selective and one that is not?
- Isoprenaline is a non-selective B-adrenoreceptor agonist it activates both heart (B1) and lung (B2) receptors
- Salbutamol is a selective B”-adrenoreceptor and only activates lung (B2) receptors
Name a drug that targets enzymes?
NSAIDs
What are the actions of NSAIDs?
- Analgesic
- Anti-pyretic (reduces fever)
- Anti-inflammatory
What is the action of NSAIDs?
- They inhibit the COX enzyme
- COX is responsible for the breakdown of arachidonic acid to prostaglandin H2 (PGH2)
How do NSAIDs inhibit COX?
- They prevent arachidonic acid from reaching the active site of COX
- They are antagonists, so they bind to the active site of COX
- NSAIDs are competitive inhibitors
How is Aspirin different to other NSAIDs?
It irreversibly blocks the active site of COX resulting in irreversible inactivation
What are the two COX isomers and what do they do?
- COX-1 found normally and widely around the body
- COX-2 induced and found mainly in inflammation
Give an example of a selective and non-selective NSAID?
- Aspirin is non-selective inhibits COX-1,2.
- Celecoxib is COX-2 selective
What are ACE inhibitors?
- They are angiotensin-converting-enzyme inhibitors
- They are anti-hypertensive
How do ACE inhibitors work?
- They prevent the conversion of angiotensin I to angiotensin I
- This means there is less angiotensin II so less bind to angiotensin receptors (AT1)
- This results in reduced vasoconstriction and thus
hypertension as well as less aldosterone release further reducing
hypertension
Name two ACE inhibitors?
- Captopril
- Enalapril
- Both are competitive inhibitors and bind to ACE active site to prevent angiotensin I from binding
Give some examples of B-lactam antibiotics?
Penicillins, amoxicillin & cephalosporins
How do B-lactam antibiotics work?
- They inhibit the biosynthesis of peptidoglycan bacterial cell walls
- This is achieved by inhibiting the activity of certain enzymes
How are drugs inactivated?
-Most drugs are excreted by the kidneys
- Lipophilic drugs are not effectively removed
- Lipophilic drugs require Cytochrome P450 (addition of OH group) to make them soluble so they can be excreted by the kidneys
- Some drugs induce or inhibit cytochrome P450 to either be removed quickly or stay in the system for longer
What is summation?
When 2 drugs used at the same time both have the expected effect
What is synergism?
- When using two drugs together makes both of the drugs more effective
- For example, paracetamol and morphine
What is blockage
- When one drug blocks the action of another
- For example, salbutamol and non-selective beta blockers
What is potentiation?
When one drug makes the other more potent, but its potency stays the same
What is bioavailability?
How much of a drug taken is used. IV is always 100% but orally, this figure can change
Name some proton pump inhibitors (PPI)
- Omeprazole
- Lansoprazole
- Pantoprazole
- Rabeprazole
How do PPIs work?
- Activated in acidic conditions
- Inhibit acid secretion
- PPIs act to irreversibly inactivate the proton pump (H+/K+ ATPase)
Name a loop diuretic?
Furosemide
How does Furosemide work?
- It inhibits symporters
- It inhibits the NKCC2 pump on the thick ascending part of the loop of Henle
How do you treat a paracetamol overdose?
- If it has been less than 1 hour since OD give activated charcoal
- If longer than this give intravenous N-acetylcysteine
Name some calcium channel blockers
- Amlodipine
- Verapamil
- Diltiazem
All used in the treatment of hypertension
How does Amlodipine work?
- It blocks voltage dependant calcium channels found in cardiac muscle and vascular smooth muscle
- This means there is less vasoconstriction useful for hypertension