Adverse Drug Reactions

Question 1

different reactions to drug can be caused by what two major differences?

Answer 1

differences in concentration of drug reaching the tissues

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

Question 2

absolute differences in dose administered can be due to?

Answer 2

error in prescription or dispensing
patient non-compliance
drug formulation

Question 3

list factors that cause relative overdose or underdose

Answer 3

Environmental exposure to chemicals
food intake
fluid intake
age
disease

Question 4

how can environmental exposure to chemicals cause relative over/underdose?

Answer 4

enzyme induction

enzyme inhibition

Question 5

how can food intake cause relative over/underdose?

Answer 5

drugs may interact chemically with components of food; this may alter their absorption
foods delay gastric emptying and alter gastric pH

Question 6

how can fluid intake cause relative over/underdose?

Answer 6

most drugs are better absorbed if taken with water e.g. may dissolve better
fluids may stimulate gastric emptying

Question 7

how can age (newborn) cause relative over/underdose?

Answer 7

more body water than adults
poorer renal function, with immature tubular secretion
an immature blood brain barrier
lower capacity for drug metabolism

Question 8

The elderly have an overall deterioration in many physiological functions that may affect what factors?

Answer 8

drug absorption
drug distribution
drug metabolism
drug excretion
organ sensitivity

Question 9

why is drug absorption affected in the elderly?

Answer 9

decreased absorptive surface of small intestine
altered gastric and gut motility
increased rate of gastric emptying

Question 10

why is drug distribution affected in the elderly?

Answer 10

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 11

why is drug metabolism affected in the elderly?

Answer 11

splanchnic and hepatic blood flow decrease by 0.3 – 1.5%/year
liver size and hepatocyte number decrease
hepatic enzyme activity and induction capacity decrease

Question 12

why is drug excretion affected in the elderly?

Answer 12

reduced renal mass
reduced renal perfusion
reduced glomerular filtration rate
reduced tubular excretion

Question 13

how does organ sensitivity affect pharmacology in the elderly?

Answer 13

elderly tend to be more sensitive to CNS active drugs

Question 14

what disease factors can affect relative over/under dosing?

Answer 14

general nutritional status
GI disorders
congestive heart failure
kidney failure
liver failure
other acute/chronic disease states

Question 15

how can general nutritional status affect relative over/underdosing?

Answer 15

unbalanced diets may lead to deficiency states and enzyme abnormalities
starvation – decreased plasma protein binding and metabolism
obesity – increased lipid fraction

Question 16

how can GI disorders affect relative over/underdosing?

Answer 16

altered drug absorption

Question 17

how can congestive heart failure affect relative over/underdosing?

Answer 17

reduced splanchnic blood flow
intestinal mucosal oedema
reduced hepatic clearance

Question 18

how can kidney failure affect relative over/underdosing?

Answer 18

decreased drug excretion leading to toxicity

water overload leading to changes in drug concentrations in different body fluid compartments

Question 19

how can liver failure affect relative over/underdosing?

Answer 19

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 20

list GI disorders than can affect relative over/underdosing

Answer 20

achlorydria
coeliac disease
Crohn’s disease