Drug Interactions

Question 1

polypharmacy may lead to what type of changes?

Answer 1

1. pharmacokinetic

2. pharmacodynamic

Question 2

what are some pharmacokinetic changes due to polypharmacy?

Answer 2

1. altered rates of absorption
2. altered protein binding (distribution)
3. different rates of metabolism
4. different rates of excretion

Question 3

what are some pharmacodynamic changes due to polypharmacy?

Answer 3

1. competition at receptors

2. non-pharmacologic interactions

Question 4

which drugs are highly protein bound in plasma?

Answer 4

1. aspirin
2. barbiturates
3. phenytoin
4. sulfonomides
5. valproic acid
6. warfarin

Question 5

T/F: it is the free drug (unbound from protein) that has its therapeutic effect

Answer 5

true

Question 6

what may happen if polypharmacy causes altered protein binding (distribution)?

Answer 6

can be a toxic buildup of the drug in the blood

Question 7

what may cause altered protein binding (distrubution) of polypharmacy?

Answer 7

1. protein binding sites become saturated
2. if pt has hypoalbuminemia (e.g. liver damage)
3. a drug is displaced from protein binding by another drug

Question 8

if drug A inhibitis the P450 enzyme that metabolizes drug B, then what will happen?

Answer 8

there will be an increased level of drug B in blood (potential toxicity)

Question 9

if drug A induces the P450 enzyme that metabolized drug B, then what will happen?

Answer 9

then there will be a decreased level of drug B in the blood

Question 10

classification of chemical interactions

Answer 10

1. additive
2. synergistic
3. potentiation
4. antagonism

Question 11

additive interactions

Answer 11

when combined effects of 2 drugs equal the sum of the effect of each agent given alone

Question 12

synergistic interactions

Answer 12

when the combined effects of 2 drugs are greater than t he sum of the effect of each agent given alone

Question 13

potentiation interactions

Answer 13

creation of a toxic effect from one drug (that is not normally toxic) due to presence of another drug

Question 14

T/F: in potentiation interactions, the second drug is usually affected

Answer 14

false, 2nd drug is usually NOT affected

Question 15

antagonism interaction

Answer 15

combined effect of 2 drugs is less than the individual agents given alone (the opposite of synergism)

Question 16

drug interaction between statins and azole antifungals

Answer 16

i.e. atorvastatin and clotrimazole

can cause…

1. rhabdomyolysis
2. kidney failure

Question 17

drug interaction between oral anticoagulants and NSAIDs

Answer 17

i.e. warfarin and ibuprofen

can cause…

1. increased INR
2. severe gastric bleeding

Question 18

drug interaction between alcohol and opioids

Answer 18

i.e. wine and hydrocodone

can cause…

1. severe drowsiness
2. increased respiratory depression

Question 19

drug interaction between proton pump inhibitors (PPIs) and abx

Answer 19

i.e. iansoprazole and ceftriaxone

can cause…

1. long QT syndrome
2. increase risk of clostridium difficile infection

Question 20

drug interaction between NSAIDs and thiazide diuretics

Answer 20

i.e. ibuprofen and hydrochlorothiazide

1. can cause increase in renal vascular resistance and sodium retention resulting in hypertension
2. can increase potassium retention resulting in hyperkalemia and arrhythmias

Question 21

drug interaction between NSAIDs and selective serotonin uptake inhibitors (SSRIs)

Answer 21

i.e. ibuprofen and fluoxetine

1. can increase bleeding
2. cause iron deficiency anemia

Question 22

drug interaction between statins and macrolide abx

Answer 22

i.e. simvastatin and erythromycin

can cause…

1. rhabdomyolysis
2. kidney failure

Question 23

drug interaction between PCN abx and oral contraceptives

Answer 23

i.e. ampicillin and drospirenone

can decrease effectiveness of birth control pill

Question 24

drug interaction between abx and immunosuppressive drugs

Answer 24

i.e. amoxicillin and methotrexate

can cause methotrexate toxicity resulting in…

1. mucositis
2. acute renal failure
3. hepatotoxicity

Question 25

drug interaction between anticonvulsants and nitromidazole abx

Answer 25

i.e. phenytoin and metronidazole

can cause phenytoin toxicity resulting in… 1. nystagmus

2. ataxis
3. coma