Pharmacology Flashcards
Define pharmacology
The study of the effects of drugs
Define pharmokinetics
How the body affects the drug
What does MADE stand for (pharmokinetics)
M= metabolism
A= absorption
D= distribution
E= excretion
Define pharmacodynamics
How the drug affects the body
What is a receptor?
A component of a cell that interacts with a specific ligand and initiates a change of biochemical events leading to the ligands observed effects
What are the 2 types of ligands?
Exogenous: eg drugs
Endogenous: eg hormones and neurotransmitters
What are 3 chemical types that interact with receptors?
Neurotransmitters
Autoacids
Hormones
What are 2 examples of a neurotransmitter?
Acetylcholine
Serotonin
What are 2 examples of an autoacid?
Local hormones:
Cytokines
Histamine
What are 2 examples of a hormone?
Testosterone
Hydrocortisone
What are 4 types of receptors?
Ligand gated ion channels
G coupled protein receptors (GPCRs)
Kinase linked receptors
Cytosolic/ nuclear receptors
What is an example of a ligand gated ion channel?
Nicotinic ACh receptor
What are ligand gated ion channels used for?
ACh binding opens pore and allows ions to move into cell and change the cells electric charge distribution
Give an example of a GPCR
Beta adrenoreceptors
What are the largest and most diverse group of membrane receptors in eukaryotes?
GPCRs
What is the function of GPCRs?
On ligand binding, GPCRs catalyse the exchange of GDP to GTP
What are kinases?
Enzymes that catalyze the transfer of phosphate groups between proteins - process is known as phosphorylation
Describe the mechanism of kinase linked receptor activation
Ligand binding causes conformational change
Phosphorylation
Signal transduction
What type of hormones use cytosolic/nuclear receptors?
Steroid hormones
How do nuclear receptors work?
Modify gene transcription
How do zinc fingers aid nuclear receptors?
Recognise discrete regions of DNA
Give 2 examples of a chemical imbalance leading to pathology
Allergy- inc. histamine
Parkinson’s- dec. dopamine
Give 2 examples of receptor imbalance leading to pathology
Myasthenia gravis- loss of nicotinic ACh receptors
Mastocytosis- increased C-kit receptors
What is EC50?
Concentration that gives half the maximal response
Define agonist
Compound that binds to a receptor and activates it
Define antagonist
A compound that binds to a receptor but does not activate it
How is intrinsic activity calculated?
Emax of partial agonist
———————————
Emax of full agonist
Can antagonists activate a receptor?
No
Define ligand
A molecule that binds to another (usually larger) molecule
What does the 2 state model of receptor activation describe?
describes how drugs activate receptors by inducing or supporting a conformational change in the receptor from “off” to “on”.
How does competitive antagonists work?
Reverse effects of agonists by competing with the agonist to bind to a receptor- prevents activation by blocking agonist binding
What effect does adding a competitive antagonist have on a dose response curve?
Curve shifts to the right
-more agonist needed to illicit the same response
How does a non-competitive antagonist work?
Binds near the receptor and prevents activation but doesn’t bind directly so agonist can still bind but not activate it
What effect does adding a non-competitive antagonist have on a dose response curve?
Shifts right and down- agonist can bind but not activate it
What is a partial agonist?
An agonist which is unable to induce maximal activation of a receptor population, regardless of the amount of drug applied
What are the 2 categories of cholinergic receptors?
Nicotinic and muscarine
What the ACh receptor for muscarinics?
mAChR
What is the receptor for nicotinics?
nAChR
What is the antagonist of muscarinic receptors?
Atropine
What is the antagonist of nicotinic receptors?
Curare
What are the agonist and antagonists of histamine receptors?
Histamine = agonist
-contracts ileum and acid secretion
Mepyramine = antagonist
-reversed contraction of ileum, no effect on acid secretion
Define affinity
How well a ligand BINDS to the receptor
Is affinity shown by antagonists or agonists?
Both
Define efficacy
How well a ligand ACTIVATES the receptor
Do agonist or antagonists show efficacy?
Only agonists
Name a drug that will permanently inactivate a receptor
BAAM irreversibly antagonises B-adrenoreceptors
Describe receptor reserve
Some agonists need only a small amount of receptors to be activated to produce the maximum response
Do partial agonists have a receptor reserve?
No- maximal response never seen
What does signal amplification determine?
How powerful the response will be
What determines how powerful a signal amplification is?
The type of tissue the receptor is based on
Describe allosteric modulation
Binding of an allosteric ligand at another site can effect an agonists effect on the receptor
Define Emax
Maximum effect a drug can produce
Define intrinsic activity (IA)
Refers to the ability of a drug-receptor complex to produce a maximum functional response
Describe inverse antagonism
A drug binds to the same receptor as an agonist but induces a response opposite to that of the agonist
Define tolerance
The reduction in a drug (agonist) effect over time
What are 3 causes of receptor desensitisation?
Uncoupled (receptor can interact with G-protein)
Receptor internalised in cell vesicle
Receptor is degraded
How do NSAIDs work?
Inhibit COX which breaks arachidoic acid to PGH2 via competitive inhibition
How do ACE inhibitors work?
Inhibit ACE by preventing angiotensin 1 converting to angiotensin 2 So less bind to receptors
What is the effect of ACE inhibitors?
-Lack of binding to AT1 receptors results in reduced vasoconstriction-> reduced hypertension
-Also reduced aldosterone -> reduced hypertension
What type of drugs are captopril and enalapril?
ACE inhibitors
How do B-lactam antibiotics work?
Inhibit biosynthesis of peptidoglycan bacteria cell walls by inhibiting enzyme activity
What are the 3 types of protein ports?
Uniporters
Symporters
Antiporters
Describe the function of a uniporter
Use energy from ATP to pull molecules in
Describe the function of a symporter
Use the movement in of one molecule to pull in another molecule against a concentration gradient
Describe the function of an antiporter
One substance moves against its gradient, using energy from the second substance (mostly Na+, K+ or H+) moving down its gradient.
What is the suffix for a proton pump inhibitor?
Prazolone
What is the function of a proton pump inhibitor (PPI)?
Inhibit acid secretion and reduce acidity to help with reflux ect
Describe the mechanism of PPIs
Irreversibly inactivate proton pumps of parietal cell causing a reduction in stomach acidity
Describe the function of diuretics
Removes water from the blood to reduce blood volume and therefore blood pressure
How do thiazides work as diuretics?
Inhibit Na+/Cl- co transporter on distal tubule of nephron to increase water loss
How does furosemide act as a diuretic?
Inhibits NKCC2 pump on thick ascending limb of LOH reducing ions in three interstitium
-reduces hyperosmolarity so less water diffuses into the blood causing water loss
What are calcium channel blockers used to treat?
Hypertension
How are calcium channel blockers used to treat hypertension?
Block Ca2+ channels in the cardiac muscle, preventing influx of Ca2+ and therefore preventing vasoconstriction
What is the suffix for general anaesthetics?
Ocaine/caine
How do local anaesthetics work?
Block voltage dependent Na channels preventing depolarisation so the action potential can not be generated- so pain is not transmitted
Which enzyme is responsible for 75% of drug metabolism?
CYPs
What are the 3 phases of pharmacokinetics at the plasma level?
UPTAKE into plasma
DISTRIBUTION from the plasma
ELIMINATION from the plasma
What occurs in a first order reaction?
Rate is directly proportional to the concentration of the drug
What occurs in a second order reaction?
Rate directly proportional to the concentration squared
What occurs in a third order reaction?
Rate directly proportional to the concentration cubed
What occurs in a zero order reaction?
Rate unrelated to the concentration of the drug
What are the 5 ways a drug can move from the site of administration to its target?
- Simple diffusion
- Facilitated diffusion
- Active transport
- Through extracellular spaces
- Non-ionic diffusion