3 - drug interactions Flashcards
what are two ways that drugs can interact
influence effectiveness by altering its availability (kinetics) or altering its interactions with its receptor (dynamic)
what is pharmacodynamics
What drug does to body
what is pharmacokinetics
what body does to drug
what is the pharmacokinetics consideration of drug interactions
how one drug may influence the effectiveness of another drug
what is the pharmacodynamic consideration of drug interactions
how one drug alters another drug’s interaction with its receptor
how does theraputic index relate to drug interactions
drugs with narrow theraputic index are most susceptible to issues with drug interactoins
what can result from a small change in availability of a drug
significant changes too outcome (too much causing toxic, too little so no therapy)
what is an antagonist interaction
drug A acts as an antagonist at receptor for drug B
is antagonist interaction a pharmacodynamic or pharmacokinetics
pharmacodynamic (drug does to body)
what is an example of an antagonist interaction?
vitamin K rich foods on warfarin
what is warfarin
anti-coagulant in patients with blood clot issues
how does warfarin work
inhibitor of Vit K epoxide reductase
this causes a reduction of clotting factors (red. VitK is used to make prothrombin)
what does VitK epoxide reductase do
recycle oxidized Vit K into reduced Vit K
what is a role of reduced vitamin K
helps make prothrombin
what is prothrombin time
measure of time required for blood to clot under a set of standard lab conditions
what is international normalized ratio
the ratio of the clotting time compared to a normal sample
what does a high what is international normalized ratio
sample requires a long time to clot
what does a low what is international normalized ratio
sample requires a short time to clot
what is the ideal international normalized ratio
2-3
what does vitamin K do to the effectiveness of warfarin
reduces it
how does vitamin K affect the effectiveness of warfarin
it is a competitive inhibitor for the enzyme (vit K epoxide reductase)
what happens to the effectiveness of warfarin if VItK is diminished
stronger effectiveness
what are synergism/additive interactions
multiple agonists/modulators that act on the same receptor leading to excessive activation
is additive/synergism interaction a pharmacodynamic or pharmacokinetics
pharmacodynamic (drug does to body)
what does synergism mean
effects that are greater than the inividual effects of the two drugs
what does additive mean
effects that are roughly the sum of the individual effects of two drugs
what is an example of excessive receptor activation (synergism additive)
bezos, alcohol, barbiturates and other GABA A receptor modulators
what is the mechanism of action of benzodiazepines
positive allosteric modulators of GABA A
what is the mechanism of action of barbiturates
positive allosteric modulators or agonists of GABA A
what is the mechanism of action of alcohol
positive allosteric modulators of GABA A
what is the mechanism of action of zolpidem
positive allosteric modulators of GABA A
is indirect interaction a pharmacodynamic or pharmacokinetics
pharmacodynamic
what is indirect interaction
the effects of multiple drugs might influence the same signalling pathway, but not necessarily the same receptor
what is an example of an indirect interaction
serotonin syndrome
what is serotonin syndrome ( cause+effect)
arise from a combination of drugs that lead to an over abundanceof 5HT in the CNS and overstimulation of 5HT receptors (especially 5-HT2A and 1A)
how do MAOIs contribute to serotonin syndrome
inhibit breakdown of 5HT
lots of them act irreversibly
how do TCAs contribute to serotonin syndrome
prevent reuptake of 5HT from synaptic cleft
how do SSRI contribute to serotonin syndrome
prevent reuptake of 5HT from synaptic cleft
how do SNRI contribute to serotonin syndrome
prevent reuptake of 5HT from synaptic cleft
how do some opioids contribute to serotonin syndrome
metabolites may have direct serotonergic effects or interfere with serotonin reuptake
how do St. John’s wort contribute to serotonin syndrome
serotonin reuptake inhibitor
how do MDMA and methamphetamine contribute to serotonin syndrome
use efflux pumps (transport in reverse)
what are 2 ways of how can you alter drug availability pharmacokinetically
drugs that alter gut motility that affect absorption
drugs that alter local blood flow can alter absorption (lidocaine+epinephrine)
how is lidocaine+epinephrine an example of pharmacokinetic drug interaction way to alter drug availability
alters absorption because the epinephrine vasoconstricts so that lidocaine can stay in the area
what are two ways that CYP can be affected by food or drugs
induce expression of specific CYP enzymes (reduce lifetime and abundance of their substrates)
inhibit CYP activity (prolong lifetime and abundance of the substrates)
what is the role of biotransformation
metabolism in the liver
what is phase 1 biotransformation
oxidation via CYP
what is phase 2 biotransformation
conjunction with large polar additions
which enzymes metabolizes warfarin
CYP3A4
which is the most common CYP enzyme
CYP3A4
which food inhibits CYP3A4
grapefruit juice
what happens to someone who has a lot of grapefruit who also takes warfarin
heightened sensitivity to warfarin or other drugs metabolized by CYP3A4
what does grapefruit juice do to CYP3A4
inhibit it
check online diagram he said hed post
make more questions
what are product monographs
where the drug interactions are listed
what is INR
the ratio of clotting time compared to a control
what does high INR mean
the samples takes a long time to clot
what does low INR mean?
sample doesn’t take long to clot
how is prothrombin time measured
in INR (international normalized ratio)
