pharmacology Flashcards
define pharmacodynamics
what a drug does to the body
define pharmacokinetics
what the body does to a drug e.g. absorption, metabolism
define efficacy
the ability of an agonist to evoke a cellular response
define oral availability
the fraction of the drug the reaches the systemic circulation after oral ingestion
define systemic availability
the fraction of the drug that reaches the systemic circulation after absorption
what is the systemic availability of drugs administered IV
100%
what can IV administration result in
high levels of drug at heart
what route of drug administration is frequently used for nocturnal
rectal
also when oral route compromised e.g. nausea and vomiting or unconscious
what is infrequently used in the UK
rectal
which route totally avoid first pass metabolism
IV, buccal and sublingual
what is the route for drugs that cause local tissue damamge
IV
what route allows rapid onset of lipid soluble drugs
IM
what route is good for volatile compounds
inhalation
what route is ideal for local effect
topical
what route can produce a smooth plasma concentration
transdermal
what drugs can move freely by diffusion
ionised drugs of low molecular weight that are not bound to protein
where does the absorption of oral drugs mainly occur
small intestine
what is the volume of distribution of a drug
the apparent volume in which it is dissolved
describe first order kinetics
rate of eliminations is directly proportional to drug concentration
define clearance
the volume of plasma created of drug in unit time
what does clearance only apply to
1st order kinetics
what does clearance determine
the maintenance dose rate
define steady state
rate of drug administration = rate of drug elimination
how many half lives does it take to reach steady state in 1st order kinetic drugs
5 half lives
define loading dose
initial higher dose of a drug given at the beginning of a course of treatment before stepping down to a lower maintenance dose
reason for LD
dec time to steady sate for drugs with long half lives
define zero order kinetics
drug initially eliminated at a constant rate, and then converted to 1st order at lower conc
zero order also called
saturation kinetics
what drugs exhibit 0 order kinetics
ethanol and phenytoin
define xenobiotic
substance that is foreign to the body
what drug is converte from inactive prodrug to active compounds
enalapril to enalaprilat
what drug gains activity
codeine to morphine
what drugs has unchanged activity
diazepam to nordiazepam
what does phase 1 in the liver do
make rug more polar
e.g. oxidation reduction, hydrolysis
what does phase 2 in the liver do
conjugation e.g. methyl group
what type proteins are cytochrome p450
haem proteins
what reactions do p450 mediate
oxidation
describe the monooxygenase p450 cycle
drug enters the cycle and leaves as hydroxy product
define glucoronidation
transfer glucoronic acid to electron rich atoms of the substrate
define hyperpolatisation
the membrane potential becomes more negative
why does Na move inward
conc and electrical gradient is inward
why does K move outward
conc gradient > electrical gradient
define absolue refractory period
no stimulus can elicit a second action potential
define relative refractory period
stronger than normal stimulus can elicit a second AP
define saltatory conduction
in myelinated axons AP jumps from one node of Ranvier to the next
what effect does Guillan Barree have on nerve conduction
slows it
where in the AP does the absolute RP occur
downstroke
where in the AP does the relative RP occur
undershoot
how do impulses spread in non myelinated axons
passively
postganglionic neurotransmitter in sympathetic division
noradrenaline
sympathetic outflow
T1-L2
thoracolumbar
why is the sympathetic innervation of the adrenal gland special
pre-ganglionic (mediated by ACh)
parasympathetic outflow
CN III, VII, IX and X and sacral spina nerves
cranioscarl outflow
how many subunits do nicotinic ACh receptors consist of
5
para - M1 pathway
Gq - stimulates PLC - inc acid secretion
para - M2 pathway
Gi - inhibit AC and open K channels - dec HR
para - M3 pathway
Gq - stimulate PLC - inc salivary gland secretion and contraction
amphetamine action
causes the release of transmitter from sympathetic post-ganglionic neurones in a manner that doesn’t require the opening of presynaptically located voltage activated Ca channels
