Week 7 - DIstribution, Metabolism + Ecretion

Question 1

What are changes in the older adult body that affects distribution of drugs? (3)

Answer 1

• increased body fat
• decreased body water
• decreased serum albumin

Question 2

Why does change in body composition change the distribution of a drug? (3)

Answer 2

• changes in body composition; increased body fat

Effect: drugs that bind to fat will have a prolonged effect
- they last longer in the body, leading to unpredictable effect

Question 3

What are 2 example medications that are affected by body composition?

Answer 3

valproic acid and diazepam

Question 4

Why does decreased body water affect distribution of drugs in the body? (2)

Answer 4

• drugs that bind to water will have an increased concentration
• higher risk of toxicity and adverse medication effect

Question 5

What are 3 example medications that are impacted by decreased body water?

Answer 5

• morphine
• digoxin
• lithium

Question 6

Why does decreased serum albumin change distribution of a drug? ie. Why do they experience decreased albumin, and the effects

Answer 6

• prolonged illness and malnutrition causes decreased serum albumin

Effect:
- higher concentrations of drugs that bind to protein albumin leads to increased risk for toxicity of medication

Question 7

What are 3 example medications affected by decreased albumin?

Answer 7

• fentanyl
• diphenhydramine
• lidocaine

Question 8

What is metabolism?

Answer 8

• process in which the body modifies the chemical structure of the medication

Question 9

What does metabolism do to drugs?

Answer 9

• changes the chemistry of the drug so it can be excreted or removed from the body

Question 10

Where does metabolism occur most prominently?

Answer 10

• liver

Question 11

What is half-life?

Answer 11

the measure of the amount of time the drug is active in the system

Question 12

What changes in the older adult’s body alter metabolism of a drug?

Answer 12

• reduced blood flow through the liver

Question 13

Why does reduced blood flow through the liver affect metabolism? (3)

Answer 13

• can lead to an increase in the amount of time the medication stays in the body longer
• increases half life
• A medication that is broken down into active metabolites (has increased half-life) increases the effect of the medication on the body

Question 14

Give an example of a medication that is affected by metabolism of the body

Answer 14

diazepam

ex. 20 year old takes 10 mg, 20 hours later they have 5 mg in blood
- 80 year old takes 10 mg, 80 hours later they have 5 mg in blood

Question 15

How does the body influence the excretion of the drug?

Answer 15

• primarily excreted through kidneys, also bile, saliva and sweat

Question 16

How do changes in the older adult influence excretion? (2)

Answer 16

• decreased blood flow through kidneys
• decreased kidney function (decreased glomerular filtration rate)

Question 17

How do changes in the older adult change the excretion of the drug?

Answer 17

• often means that the drug is in the body longer and increases the risk for drug toxicity

Question 18

What is used to indicate the efficiency of the glomerular filtration rate? (2)

Answer 18

• creatinine clearance
• therefore decreased creatinine clearance should lead to a decrease in dosage of some medications

Question 19

Age-related changes can be compounded by co-morbidities. Give 2 examples

Answer 19

1. Renal function is affected by the presence of comorbidities
2. decreased renal function results in reduction in drug clearance (or the drug stays in the body longer)

Question 20

What should the clinician do to compensate for changes in renal function? (3)

Answer 20

• know what normal kidney function is in the older adult
• blood levels of creatinine indicate kidney
• older adults should start with lower doses of medications