Flashcards in Pharmacology Deck (77):
What a drug does to the body - biological affects and mechanism of action
What the body does to a drug - absorption, distribution, metabolism and excretion
Define an agonist
A drug that binds to a receptor to produce a cellular response
Define an antagonist
A drug that blocks the action of an agonist
The strength of association between a ligand and receptor
The ability of an agonist (not antagonist) to evoke a cellular response
Define competitive antagonism
When an agonist and antagonist both bind to the same orthosteric site
Define non-competitive antagonism
When an agonist and antagonist bind to different sites - the antagonist binds to an allosteric site
Which type of drugs readily cross the lipid bilayer?
Which environments do acids dissociate more?
At high pH - acids donate protons, at high pH theres less H+ ions
Which environment makes it more likely for a base to remain basic?
At Low pH - bases accept protons and theres more protons available at a low pH
The pH at which 50% of a drug is ionised and 50% is unionised
What is oral availability?
The fraction of the drug that reaches the systemic circulation after ingestion
What is systemic availability?
The fraction of the drug that reaches the systemic circulation after absorption
What does the height of the Cm determine?
The rate of diffusion
What three factors affect drug absorption?
Solubility, chemical stability and lipid solubility
What happens to the conc. of H+ ions as the pH decreases?
Which pH do acids dissociate more in and why?
High pH - less H+ ions so they're easier to give away
Which pH do bases dissociate more in and why?
Low pH - there are more H+ ions so they are easier to accept
What is the henderson hasselbaclch equation?
pKa - pH = log [HA]/[A-]
what is oral availability?
The fraction of drug that reaches the systemic circulation after oral ingestion
What is systemic availability?
The fraction that reaches the systemic circulation after absorption
Which drugs move readily by diffusion?
What is the equation for the volume of distribution?
Vd = dose/plasma concentration
TR = Maximum tolerated concentration/minimum effective concentration
How is the initial conc. of a drug calculated?
Co = Dose/ volume of distribution
what does doubling the dose do to a first order kinetic drug?
Doubles the duration of action but does not alter the half life
what does clearance determine?
The maintenance does rate - i.e. the does per unit time to maintain a steady plasma conc.
What does changing the rate of administration do in relation to steady state?
Alters the value of the steady state not how long it takes to get there
Foreign to the body
What does phase 1 of drug metabolism do?
Oxidise/reduce/hydrolysis = makes drug more polar
What does phase 2 of drug metabolism do?
Conjugates = adds an endogenous compound to increase polarity
Where are cytochrome proteins found?
In the ER of the liver
Which 3 cytochrome gene families are important in the liver?
CYP1, CYP2 and CYP3
What is step one in the monoocygenase P450 cycle?
Drug enters the cycle as a drug substrate
What is step two in the monoocygenase P450 cycle?
Molecular oxygen provides two atoms of oxygen
What is step three in the monoocygenase P450 cycle?
one atom of oxygen is aded to the drug to yield hydroxyl and the other forms water
What are the three processes in renal excretion?
Active tubular secretion
Passive reabsorption by diffusion across the tubular epithelium
How are drugs which are highly protein bound secreted?
Via tubular secretion
What does an alkaline urinary pH do to the excretion of acids?
What does an acidic urinary pH do to the excretion of bases?
The membrane potential becomes less negative
The membrane potential becomes more negative
Why does Na+ flow inward?
Both the conc. gradient and electrochemical gradient is inward
Why does K+ flow outward?
The conc. gradient is outward and the electrochemical gradient is inward however the conc. gradient is stronger
When are action potentials generated?
When threshold is reached
Which type of feedback is Na+ channels?
Which type of feedback is K+ channels?
Which state do Na+ channels have to be in to conduct?
Which state do Na+ channels have to be in to be non-conducting?
Inactive or closed state
Which cells are mylenating in the PNS?
Which cells are mylenating in the CNS?
Which neurone is longest in the sympathetic division of the ANS?
Which neurone is longest in the parasympathetic division of the CNS?
What are the sympathetic neurotransmitters?
Pre - ACh
Post - NA
What is the parasympathetic neurotransmitter?
ACh - for pre and post
Craniosacral outflow - CN III, VII, IX and X
Which receptors are activated in the sympathetic division?
G-protein coupled adrenoreceptors
Which receptors are activated in the parasympathetic division?
G-protein coupled muscarinic acetylcholine receptors
What kind of protein is the receptor of G-protein?
Integral membrane protein
What kind of protein is the G-protein?
Peripheral membrane protein
When there is no signalling what is bound to the G-protein?
When there is signalling what is bound to the G-protein?
Which part of the G-protein attaches to the signal molecule?
What acts as an enzyme to hydrolyse GTP to GDP?
What substance converts ACh back into choline?
What does M1 pair with and what is its action?
Gq - increases acid secretion in the stomach
What does M2 pair with and what is its action?
Gi - Decreases HR
What does M3 pair with and what is its action?
Gq - Bronchial contraction
Which substances are involved in the re-uptake of NA?
U1 and U2
What substances metabolise the NA once it has been taken back?
what does B1 pair with and what is its action?
Gs - Increased HR and force
What does B2 pair with and what is its action?
Gs - Bronchial relaxation and relaxation of vascular smooth muscle
What does a1 pair with and what is its function?
Gq - Contraction of vascular smooth muscle