Pharmacokinetics II Flashcards Preview

BMS 242 - Core Phys/pharm > Pharmacokinetics II > Flashcards

Flashcards in Pharmacokinetics II Deck (51)
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1

What are the 4 major water compartments in the body?

What percentages of the body weight do these conribute to?

1) Extracellular fluid

2) Intracellular fluid (20-40%)

3) Transcellular fluid (2.5%)

4) Fat (20%)

2

How does the volume of a compartment affect a drug?

Concentration of a drug in that compartment at equilibrium

3

What percentage do the water compartments contribute to the body weight?

50-70%

4

What are the 3 components of extracellular fluid and how much body weight percentage?

1) Plasma (4.5%)

2) Interstitial fluid (30-40%)

3) Lymph (1-2%)

5

What is interstitial fluid?

Extracellular fluid which bathes cells and tissues

6

How are drugs distributed to different parts of the body?

In the plasma

7

Where is the bioavailability of a drug measured?

In the plasma

8

How does fat impact the pharmacokinetics of a drug? (4)

- Made of lipids

- Non- polar drugs can easily enter and accumulate here

- Poorly perfused

- Varies between different people

9

Examples of the compartments of the body which are tightly regulated and why(2)

The foetus
- Protected by the placenta

The CNS
- Protected by the BBB

10

What is the distribution of the drug based upon?

- Permeability
- Lipid solubility

11

What is the BBB impermeable to and why?

Water soluble molecules, they have poor lipid solubility

12

Examples of drugs which can't cross the BBB?

- Antibiotics
- Chemotherapy drugs

(poor lipid solubility)

13

Examples of which molecules easily cross the BBB?

Lipid soluble
- Ethanol
- Caffeine

14

What happens to tight junctions during inflammation?

Become 'leaky'

15

Where is the chemoreceptor zone in the body and what does this do?

- Outside of the BBB
- Induces vomiting - can happen during drug treatments

16

How does the protein albumin affect the free concentration of drugs in the plasma?

- Binds to acidic drugs
- Reduces the concentration of drug in the plasma

17

What are the 3 considerations of drug dose, regarding albumin?

When low doses of free drug are needed- need to increase dose to overcome binding to albumin

When high doses of free drug are needed - already taking a high dose
- Binding to and from albumin can decrease/increase the concentration of drug in the plasma - dangerous

Taking another drug can displace the original drug from albumin - increasing free concentration of the original drug

18

How does the partition into body fat effect the free concentration of drug in compartments why is this a disadvantage?

- Drug accumulates in the body fat

- Changes the amount and duration of drug in the body

- Difficult to predict the concentration of drug where you want it to act

19

What drugs are more likely to partition into the body fat?

Lipid soluble drugs

20

What affects drug concentration in the body?

Absorption (permeability, lipid solubility, into fats)
Distribution
Metabolisation
Excretion

21

Where does drug metabolism mostly occur?

In the liver

22

What are the 2 biochemical reactions in the liver?

Phase 1 - catabolic reaction

Phase 2 - synthetic (anabolic) reactions

23

What happens in phase 1 in the liver?

- Produce more reactive compound
- By oxidation, reduction or hydrolysis

- Adds a reactive group (-OH) which serves as a point of attack for phase 2 reaction

24

What happens in phase 2 in the liver?

- Conjugation to produce an inactive product
-

25

What is conjugation?

Attachment of a substituent group

26

What are the microsomal enzymes present in the liver?(3)

- Cytochrome P450
- Alcohol dehydrogenase
- MAO

27

Where is cytochrome P450 found?

Embedded in the membrane of the smooth muscle endoplasmic reticulum of the liver

28

Which enzyme can cause drug concentration to increase and why?

Alcohol dehydrogenase as it is easily saturated

29

What does enzyme induction cause?

- Increase metabolic enzyme in the body
- Cause drug to have a less effect as concentration decrease

30

What does drug metabolism depend upon?

The ability of the drug to cross the membrane into the liver