Drug interactions

Question 1

5 general types of drug interactions

Answer 1

1. pharmacodynamic
2. combined products/duplications
3. combined toxicities
4. pharmacokinetics
5. direct vs. indirect

Question 2

4 types of pharmadynamic interactions

Answer 2

1. duplications (tylenol and neocitran)
2. additive (2 B blokers)
3. synergystic (1+1=3)
4. antagonistic

Question 3

4 types of pharmacokinteic interactions

Answer 3

1. absobtion
2. distribution
3. metabolizm
4. excretion

Question 4

7 interactions involving absorbtion

Answer 4

1. absorbtion (into circ) vs. adsorption (stuck in bag)
2. physiochem interactions (drug sticks together)
3. GI motility
4. changes in flora
5. mucosal damage
6. gastric pH
7. drug transporters

Question 5

what happens to acidic drug when increase the pH

Answer 5

more go into charged form (less absorption)

Question 6

what happens to basic drug when increase the pH

Answer 6

more go into uncharged form (more absorption)

Question 7

what are 2 main types of drug transporters

Answer 7

1. uptake transporter (solute carrier linked SLC superfamily)
2. efflux transporters (ABC superfamily)

Question 8

what happens with fenofexadine and juices

Answer 8

inhibits the OATP transporter and lower absorption

Question 9

what happens with digoxin and p-glycoprotein inhibitor

Answer 9

pgp is efflux tranporter, so inhibition means too much digoxin

Question 10

5 factors influencing distribution

Answer 10

1. displacement from plasma proteins
2. displacement from tissue binding sites
3. changes in blood flow
4. alterations in local tissue barriers
5. interactions at drug transporters

Question 11

what is p-glycoprotein

Answer 11

efflux tranporter (also in brain)

Question 12

what happens if inhibit an efflux transporter in placenta (BCRP)

Answer 12

fetus gets more of the drug

Question 13

3 examples of changes in metabolism

Answer 13

1. combined toxity
2. inhibition of metabolizing enzymes (within hours)
3. induction of metabolizing enzymes ( may take days)

Question 14

what happens in we don’t metabolize terfenadine

Answer 14

don’t degrade and can cause long Q-T interval

Question 15

what does grapefruit juice do

Answer 15

inhibits CYP3A4, which metabolizes 50% of drugs

Question 16

why might a birth control fail

Answer 16

induction of a metabolozer of est and prog from antibiotics

Question 17

4 interactions involving excretion

Answer 17

1. combined toxicity - one drug knocks out kidney
2. inhibition of transporters
3. induction of transporter
4. pH (uncharged drugs can be reabsorbed)

Question 18

what are OATs (organic anion transporters)

Answer 18

1. usually uptake transporters

2. substrates usually organic anions

Question 19

what 2 things does st. johns wort do to digoxin

Answer 19

1. induces CYP3A4
2. induces pgp
   lowers digoxin [c]

Question 20

3 methods of investigating interactions

Answer 20

1. in silico
2. in vivo - in humans
3. in vitro - in organs or cells

Question 21

4 reasons to know interactions

Answer 21

1. understand plasma [c]
2. predict plasma [c]
3. avoid adverse interaction
4. create beneficial interactions

Question 22

4 ways to avoid interactions

Answer 22

1. ask PT the right questions
2. examine ingredients and properties of drugs
3. decide if interaction in clinically relevant
4. decide if you can prevent by adjusting the dose