Drug Interactions

Question 1

what kind of things may interact with medication? (5)

Answer 1

Food
Drinks
Smoking
Long-term conditions
Other drugs

Question 2

what four things in absorption can cause drug interactions?

Answer 2

Binding
PH change in stomach
Slow gastric emptying
Increased gastric emptying

Question 3

what 1 thing in distribution can cause drug interactions?

Answer 3

Changes in protein binding (displacement by one drug for another, releasing the other drug into the free plasma)

Question 4

What is the one thing that causes drug interactions in the metabolism stage?

Answer 4

inhibition and induction of the CYP450 enzymes

Question 5

what happens to the rate of elimination if the CYP 450 enzymes are inhibited?

Answer 5

The rate of elimination is decreased

Question 6

what happens to the rate of elimination when the CYP 450 enzymes are induced?

Answer 6

The rate of elimination is increased for hepatically metabolised drugs

Question 7

name 3 CYP450 inhibitors

Answer 7

sodium valproate
Omeprazole
Grapefruit juice
Fluconazole

Question 8

what happens to the bioavailability of a drug when the CYP 450 Enzyme is inhibited?

Answer 8

The bioavailability of the drug increases

Question 9

what happens to the bioavailability of a drug when the CYP 450 Enzyme is induced?

Answer 9

Bioavailability decreases

Question 10

name 3 CYP450 inducers?

Answer 10

Gliclazide
Carbamazepine
Phenytoin

Question 11

give 2 medication examples of drugs that interact with eachother after biotransformation.

and what enzyme is inhibited during this process

Answer 11

Omeprazole inhibits CYP2C19, which converts clopidogrel into its active metabolite, therefore reduces the antiplatelet effect

fluoxetine inhibits CYP2D6, which converts codeine into morphine which means there is a reduced pain relief.

Question 12

give 3 examples of drug interactions during excretion.

Answer 12

nSAIDs use the same active transport mechanism as methotrexate, so taking both can reduce excretion and cause possible methotrexate toxicity

Changes in your inflow and P H. (diuretics increase urine flow and excretion)

Weak acids are more rapidly excreted by alkaline

Question 13

What causes pharmacodynamic drug interactions?

Answer 13

When drugs have a similar or antagonistic affect or side-effects

Question 14

where do pharmacodynamic drug interactions occur? (2)

Answer 14

action sites (competition at receptor)
on the same physiological system (CNS, BP, clotting etc)

Question 15

pharmacodynamic drug interactions are…

Answer 15

Predictable from pharmacology
Likely to occur across classes

Question 16

why my drug interactions occur at an action site?

Answer 16

One drug may have a great affinity for the action site

Question 17

provide an example of the additive affect?

Answer 17

The use of two antihypertensive medications can reduce blood pressure in a more desirable way, as it provides earlier and longer lasting affects compared to just taking one medication

Question 18

what 3 things can increase the risk of pharmacodynamic drug interactions?

Answer 18

1- polypharmacy
2- acute on chronic conditions
3- Care across different settings

Question 19

what four things can be done to avoid pharmacodynamic interactions?

Answer 19

1- taking a drug history, including daily habits (eg. smoking, herbal remedy etc.)
2- considering high-risk drugs with a narrow, therapeutic window
3- electronic prescribing and decision support tools
4- Regional and local medicine information services

Question 20

what are the four levels of the drug interaction rating system in the BNF

Answer 20

Severe
Moderate
Mild
Unknown

Question 21

According to the BNF, what is a severe drug interaction?

Answer 21

The result may be life-threatening, or have permanent detrimental effect

Question 22

according to the bnf, what is a moderate drug interaction?

Answer 22

Could cause distress or partially incapacitate, but unlikely to be life-threatening result in long-term affects

Question 23

according to the BNF, what is a mild drug interaction?

Answer 23

Unlikely to cause concern or incapacitate, a majority of patients

Question 24

According to the BNF, what is an unknown drug interaction?

Answer 24

A predicted interaction with insufficient evidence to guess the outcome

Question 25

What are the four types of evidence in the BNF?

Answer 25

Study
Anecdotal
Theoretical
Action messages

Question 26

define a bnf caution?

Answer 26

If a safer alternative cannot be found, the drug may be prescribed while the patient is able to be monitored closely

Question 27

What is the bnf’s description of a contraindication?

Answer 27

a symptom or medical condition that is a reason for a patient not to receive a procedure or medication

Question 28

give 4 examples of things that could be a contraindication for medication

Answer 28

age
Pregnancy
Disease or disorders
Interacting medication