week 18 p2

Question 1

What does bioavailability mean

Answer 1

• Reflects the fraction of drug absorbed in the systemic circulation when the drug is given orally
  
  • Total Available of drug that reaches the systemic circulation
  • Neglects absorption
  • Measures by comparing area-under0the curve (AUC) of the drug when measurement of the plasma are made from orally
  • Reduction in total drug delivered to the systemic circulations first pass effect
  • Reason why its known as that it losses the drug via first through GI tissues and liver before the systemic circulation

Question 2

What is the equation for Bioavaiblity

Answer 2

• BA=AUCo/AUCiv x100
• AUOo= oral
AUCiv= intravenous

Question 3

What happens after the drug is in system circulation

Answer 3

drug distribution in tissues

Question 4

4. What is distribution and modulation factors mean

Answer 4

• The process of transferring drug/chemical from the bloodstream to tissues- known as Distribution

Question 5

What is distribution effected by

Answer 5

ionisation state and pH of the environment: ions trapping, non ionised drugs and chemical can cross cell membrane by passive diffusion

. Lipophilicity: Lipophilicity drugs that can cross cells membrane and blood and brain stream ( as its more preamble) and lipophilicity drugs accumulate in the fattest fat tissue e.g. breast

Question 6

How is disruption of drugs effected

Answer 6

• Through binding of drugs to proteins
  
  • In the blood drugs are transported in free unbound drug and reversable bond to blood components
  • E.g. albumin, alpha-1 and lipoprotein
  • Acidic drugs usually bound to albumin
  • Basic drugs usually bound to apha-1 and lipoprotein or both

Question 7

Another way that distribution is affected

Answer 7

• Binding of tissues
• Accumulation of drugs in tissues can prolong drug action
• Due to the tissues this releases accumulated drug as the plasma drug decreases
Lead to toxicity

Question 8

What is the threptic effects of binding of tissues

Answer 8

• Bisphonate compound bine to bone matric cells
• Rifanmoin and accumulated in the brain
Digitoxin accumulation in heart muscle

Question 9

9. How is the distributions of drugs get into the tissues effected

Answer 9

• Rate of of blood flow to tissues- perfusion
• Tissue mass
Characteristics between blood and tissue

Question 10

10. What does distribution equilibrium mean

Answer 10

• Enter and exit rate are the same between blood and tissue

Is reached more in rich vascularised areas

Question 11

What does distribution after equilibrium mean

Answer 11

• Drug concentrate and in extracellular fluid are reflected by plasma concentration

Question 12

What does it mean by volume of distribution

Answer 12

• Volume fluid into the total drug administrated would have to be diluted to produce the concnetration in plasma

Question 13

Why is plasma concentration important in this

Answer 13

• Retention of a drug in the plasma reflect binding to plasma protein

Question 14

Equation of volume of distribution

Answer 14

• Concentration= amount of drug/volume

Volume= concentration x amount of drug

Question 15

Eg of VOD

Answer 15

• if I five you 100mg of drug after that I take a blood sample and measure the plasma concentration is 10mg/l
100mg / 10mg/l = 100l

Question 16

15. What does it means If the drugs are highly bound to tissues or proteins

Answer 16

• Very little drug in the circulation
• Low plasma concentration
Higher volume of distribution

Question 17

16. What happens when drugs stay in prophetically stay in the circulation

Answer 17

Higher plasma concertation

Lower volume of distribution

Question 18

What is therapy successful

Answer 18

• is linked to unbound drug

Question 19

What is real vod

Answer 19

• Vd can also be related to body weight

• E.g. 70kg
Volume of distribution is related in liters or litres per body weight (kg/l)

Question 20

15. Ego volume for distribution is 5L and Herceptin is suppose to be4L

Answer 20

• High molecular weight drugs

Drugs can bind to plasma extensively

Question 21

16. E.g. the VD is 6-14L and ethanol drug is suppose to be 7-14L

Answer 21

• Lower molecular weight

But are hydrophilic