Drug Interactions Flashcards
polypharmacy may lead to what type of changes?
- pharmacokinetic
2. pharmacodynamic
what are some pharmacokinetic changes due to polypharmacy?
- altered rates of absorption
- altered protein binding (distribution)
- different rates of metabolism
- different rates of excretion
what are some pharmacodynamic changes due to polypharmacy?
- competition at receptors
2. non-pharmacologic interactions
which drugs are highly protein bound in plasma?
- aspirin
- barbiturates
- phenytoin
- sulfonomides
- valproic acid
- warfarin
T/F: it is the free drug (unbound from protein) that has its therapeutic effect
true
what may happen if polypharmacy causes altered protein binding (distribution)?
can be a toxic buildup of the drug in the blood
what may cause altered protein binding (distrubution) of polypharmacy?
- protein binding sites become saturated
- if pt has hypoalbuminemia (e.g. liver damage)
- a drug is displaced from protein binding by another drug
if drug A inhibitis the P450 enzyme that metabolizes drug B, then what will happen?
there will be an increased level of drug B in blood (potential toxicity)
if drug A induces the P450 enzyme that metabolized drug B, then what will happen?
then there will be a decreased level of drug B in the blood
classification of chemical interactions
- additive
- synergistic
- potentiation
- antagonism
additive interactions
when combined effects of 2 drugs equal the sum of the effect of each agent given alone
synergistic interactions
when the combined effects of 2 drugs are greater than t he sum of the effect of each agent given alone
potentiation interactions
creation of a toxic effect from one drug (that is not normally toxic) due to presence of another drug
T/F: in potentiation interactions, the second drug is usually affected
false, 2nd drug is usually NOT affected
antagonism interaction
combined effect of 2 drugs is less than the individual agents given alone (the opposite of synergism)
drug interaction between statins and azole antifungals
i.e. atorvastatin and clotrimazole
can cause…
- rhabdomyolysis
- kidney failure
drug interaction between oral anticoagulants and NSAIDs
i.e. warfarin and ibuprofen
can cause…
- increased INR
- severe gastric bleeding
drug interaction between alcohol and opioids
i.e. wine and hydrocodone
can cause…
- severe drowsiness
- increased respiratory depression
drug interaction between proton pump inhibitors (PPIs) and abx
i.e. iansoprazole and ceftriaxone
can cause…
- long QT syndrome
- increase risk of clostridium difficile infection
drug interaction between NSAIDs and thiazide diuretics
i.e. ibuprofen and hydrochlorothiazide
- can cause increase in renal vascular resistance and sodium retention resulting in hypertension
- can increase potassium retention resulting in hyperkalemia and arrhythmias
drug interaction between NSAIDs and selective serotonin uptake inhibitors (SSRIs)
i.e. ibuprofen and fluoxetine
- can increase bleeding
- cause iron deficiency anemia
drug interaction between statins and macrolide abx
i.e. simvastatin and erythromycin
can cause…
- rhabdomyolysis
- kidney failure
drug interaction between PCN abx and oral contraceptives
i.e. ampicillin and drospirenone
can decrease effectiveness of birth control pill
drug interaction between abx and immunosuppressive drugs
i.e. amoxicillin and methotrexate
can cause methotrexate toxicity resulting in…
- mucositis
- acute renal failure
- hepatotoxicity
drug interaction between anticonvulsants and nitromidazole abx
i.e. phenytoin and metronidazole
can cause phenytoin toxicity resulting in… 1. nystagmus
- ataxis
- coma
