drug interactions

Question 1

what are the types of pharmacodynamic drug interactions

Answer 1

additive: same effect on body
synergistic: similar effect on the body
duplications: same drug in 2 different products

Question 2

Fill in the blank.

________ are common sites of drug interactions

Answer 2

drug receptors

Question 3

Where can drug interactions occur

Answer 3

1. the same site on the same receptor
2. different sites on the same receptor
3. distinct locations on the body

Question 4

how are opiods an example of PD interactions that illicit a greater effect?

Answer 4

morphine, codeine, fentanyl are all agonists that bind to opiod receptors and activate them

Question 5

give an example of drugs that interact to produce a lesser effect

Answer 5

we see antagonistic effects when naloxone is introduced to fentanyl due to competitive binding,

Question 6

pseudo-irreversible

Answer 6

this is similar to covalent bonding in the body where the drug covalently binds so it doesn’t matter how much antagonist you add, there will be no notable difference

Question 7

allosteric binding

Answer 7

the drug will bind to one part of the enzyme and this will cause the other part of the enzyme to change confirmation

Question 8

tylenol + neocitran

Answer 8

example of duplicayion where both drugs contain acetaminophen

Question 9

propanolol + metaprolol

Answer 9

example of additive PD interation that lowers blood pressure

Question 10

ethanol + diazepam

Answer 10

example of synergistic that are CNS depressants

Question 11

morphine + naloxone

Answer 11

example of antagonistic interactions where they both bind to opiod receptors

Question 12

when will drug effects be increased

Answer 12

when the same receptors are activated by 2 or more drugs binding to the same site
drug binds to receptor and triggers conformational change, facilitating a second drug binding at different site on same receptor

Question 13

where will drug effects be decreased

Answer 13

when agonist and antagonist that bind to the same receptor are given together
a drug binds to a receptor, causing a conformational change that will hinder the binding of the second drug
drugs that have opposing clinical effects by different mechanisms

Question 14

what interactions affect absorption

Answer 14

physiochemical properties
change in bacterial flow
gastric pH
drug transporters

Question 15

how is the anticoagulant effect of heparin lost in the presence of protamine sulphate

Answer 15

because the drugs have opposing charges they are attracted to each other and their clinical effects are reduced

Question 16

dissolution

Answer 16

when the therapeutic agent may dissolve in a material

Question 17

what can we do to the pH environment of urine trap a basic drug

Answer 17

in order to trap a basic drug in urine we can make the urine more acidic

Question 18

What effect will a cathartic have on the GI motility

Answer 18

they will increase GI motility and may increase rate of absorption of drugs

Question 19

what effect will an opiod have on the GI motility

Answer 19

it will decrease GI motility and also the rate of gastric emptying

Question 20

what type of drugs damage the GI mucosa? what does this mean for other drugs moving through the GI?

Answer 20

non-steroid anti-inflammatory drugs damage the barrier function of the GI.

If the barrier is damaged, it will be easier for other drugs to pass and be absorbed

Question 21

what are the 2 types of drug transporters in the body?

Answer 21

influx and efflux

Question 22

what is the effect if drugs get quickly moved to the small intestine

Answer 22

this will result in a faster absorption and the Cmax is reached faster and can result in faster onset of action

Question 23

how is digoxin moved through the body and where is it excreted

Answer 23

digoxin is moved out of body by MDR 1 efflux transporter, where it will be eliminated by kidney

Question 24

why does the concentration of digoxin double when propafenone is introduced to the body

Answer 24

because propafenone inhibits the activity of MDR-1 the efflux transporter responsible for carrying digoxin out of the body

Question 25

fill in the blank.
fruit juices inhibit some______

Answer 25

OATPs

Question 26

what is the effect of this inhibition of OATP. Give a specific drug that is affected by this inhibition

Answer 26

grapefruit juice can decrease the absorption of fexofenadine, an anti-histamine. This is because grapefruit juice inhibits the OATP that carries the drug to its absorption site

Question 27

describe the process of fexofenadine journey in the body in the presence of grapefruit juice

Answer 27

fexofenadine enters the body and goes to the intestines from the stomach with the help of OATP1A2 but grapefruit juice inhibits this transporter’s ability to properly carry fexofenadine to where it needs to go

Question 28

plasma proteins bind to drugs where it will distribute throughout the body. changes in what will alter the drug’s distribution?

Answer 28

changes in blood flow

Question 29

describe the usual interactions warfarin has with the body and the changes when phenytoin is introduced?

Answer 29

usually warfarin experiences plasma protein binding with albumin, but phenytoin outcompetes warfarin when it comes to binding and thus leaving more free drug of warfarin to give therapeutic affect

Question 30

what is chelation

Answer 30

chelation is where a drug binds to metal ions

Question 31

what is the effect of chelation. Is it usually a good or bad thing?

Answer 31

chelation can help reduce metal toxicity, as the drug will grab it and carry it to be eliminated

Question 32

what drug has a chelating effect with iron

Answer 32

fexofendadine

Question 33

if loperamide, an anti-diarrhea drug, is an opiod, does this mean you ca get high?

Answer 33

no you can’t because the drug cannot cross the blood brain barrier

Question 34

what drug is an MDR 1 inhibitor

Answer 34

quinidine, an anti-arrythmic drug

Question 35

Give an example of a drug that inhibits drug metabolizing enzymes

Answer 35

erythromycin can lead to terfenadine toxicity as it inhibits the enzyme responsible for metabolizing terfenadine

Question 36

what specific enzyme does erythromycin inhibit

Answer 36

CYP3A4

Question 37

why is it not recommended for people to take oral contraceptives with anti-biotics and seizure medication

Answer 37

this is because these medications increase the metabolizing effect of CYP3A4, leading to a decrease in estrogen levels that are usually higher when taking contraceptives

Question 38

why do we need to increase the dose of warfarin, anti-coagulant when taken with phenobarbital

Answer 38

phenobarbital is a CYP2C9 inducer, the enzyme responsible for metabolizing warfarin. Phenobarbital causes a reduction in anti-coagulant effect

Question 39

if we know that only uncharged drugs can be reabsorbed, will a basic/acidic drug be more likely to be trapped in urine

Answer 39

acidic drug will be trapped because urine is usually more basic and if the acidic drug is in a protonated form, it will be charged, making it more difficult to be re-absorbed

Question 40

how does probenecid inhibit penicilin secretion

Answer 40

penecilin is mostly secreted by kidneys meaning it is excreted by basic urine - penicilin is acidic

penecilin is also an OAT substrate meaning OAT transports it to the kidney to be excreted

probenecin is an OAT inhibitor. if we inhibit OAT, it cannot carry penecilin to be eliminated, meaning it will stay in the body longer

Question 41

what are the different ways we can investigate drug interactions

Answer 41

in silica- computer investigations
in vivo- humans or animals
in vitro- organs and cells expressed in humans