Adverse Drug Reactions

Question 1

What are the 2 main reasons different people have different adverse reactions to drugs?

Answer 1

Differences in conc of drug reaching the tissue

Differences in response of target tissues to the same degree of stimulation

Question 2

What are some reasons there could be absolute differences in doses of drugs adminsitered?

Answer 2

Error in prescription
Error in dispension
Patient non compliance

Question 3

What are some factors that could cause overdose or underdose

Answer 3

Environmental factors such as exposure to chemicals, enzyme induction/inihibiton
Food intake 
Fluid intake 
Age
Disease

Question 4

How might food intake cause drug overdose or underdose?

Answer 4

Drugs might interact chemically with components of food

Foods might delay gastric emptying or alter gastric pH

Question 5

How might fluid intake cause drug overdose or underdose?

Answer 5

Most drugs are absorbed better if taken with water

Fluid might stimulate gastric emptying

Question 6

How does being a newborn affect how drugs work on the body?

Answer 6

Newborns have more body water, poorer renal function, immature blood brain barrier, lower capacity fro drug metabolism

Question 7

How does drug absorption differ in the elderly?

Answer 7

They have a decreased intestinal absorptive surface
They have altered gastric and gut motility
They have an increased rate of gastric emptying

Question 8

How does drug distribution differ in the elderly?

Answer 8

Reduced lean body mass and body water, relative increase in fat
Lipid soluble drugs have increased Vd and decreased blood levels
Water soluble drugs have decreased Vd and increased blood levels
Reduced plasma albumin, so fewer plasma protein binding sites

Question 9

How does drug metabolism differ in the elderly?

Answer 9

Splanchnic and hepatic blood flow is reduced
Liver size and hepatocyte number falls
Hepatic enzyme activity and induction capacity fall

Question 10

How does drug excretion differ in the elderly?

Answer 10

There is over reduced renal function, this includes renal mass, perfusion, GFR, tubular excretion

Question 11

How does organ sensitivity differ in the elderly?

Answer 11

They tend to be more sensitive to CNS active drugs

Question 12

How does a state of starvation/malnutrition affect how drugs work on the body?

Answer 12

There is decreased plasma protein binding and metabolism

Question 13

How do GI disorders affect how drugs work on the body?

Answer 13

They alter drug absorption

Question 14

How does congestive heart failure affect how drugs work on the body?

Answer 14

Reduced splanchnic blood flow
Intestinal mucosal oedema
Reduced hepatic clearance

Question 15

How does kidney failure affect how drugs work on the body?

Answer 15

Reduced excretion of the drug leading to toxicity

Water overload which changes drug conc in different parts of the body

Question 16

How does liver failure affect how drugs work on the body?

Answer 16

Reduced metabolism
Reduced first pass metabolism (hence increased bioavailability)
Decreased biliary secretion and hence decreased removal
Decreased albumin synthesis and hence reduced plasma protein binding

Question 17

What pathway is required for warfarin to be eliminated?

Answer 17

Cytochrome P450

Question 18

How is cytochrome P450 involved with warfarin?

Answer 18

It is needed to eliminate warfarin

Question 19

What is INR used for?

Answer 19

It is a standardised measure of blood clotting time

Question 20

How is INR calculated?

Answer 20

Ratio of prothrombin time to a control sample raised to the power of the ISI value for the tissue factor used

Question 21

What does it mean if INR is falling?

Answer 21

Blood is clotting slower

Question 22

What is digoxin used for and how does it work?

Answer 22

It decreases heart rate, it does this by inhibiting myocardial sodium potassium ATPase

Question 23

What is it important to measure when someone is on digoxin? Explain why

Answer 23

Potassium levels
If hypokalemic digoxin has less K+ to compete with at binding sites so there are excess effects
If hyperkalemic, there are likely kidney problems which means digoxin is not cleared effectively and again there are excess effects

Question 24

What is a pharmacokinetic side effect?

Answer 24

A side effect arising because the drug effects the body

Question 25

What is a pharmacodynamic side effect?

Answer 25

A side effect arising because the body effects the drug