Integrated pharmacokinetics absorption

Question 1

Components of pharmacokenetics

Answer 1

• Drug action on enzyme and receptors
• Adminstration and absorbtion muscle, gut and blood
• Drug distribution into tissue depots how much in plasma
• Drug metabolism via liver and target tissue

Question 2

Therapeutic window

Answer 2

• Drug is required to be absorbed well
• Magnitude of drug effect related to drug available
• Ideal staying in theraputic window
• First order kenetics increase then decrease

Question 3

Kenetics may not be true if

Answer 3

• Drug is mediated through a metabolite
• The drug is irreversible
• Follow diffrent kinetics in the target compartment
• Alcohol consumption becomes zero order kenetics

Question 4

Passive diffusion

Answer 4

• Major mechanism of drug delivery
• Dependant on ability of drug crossing lipid bilayer across cell membrane

Question 5

Rate of diffusion is dependant on

Answer 5

• Surface area
• Thickness of membrane
• Molecular size & lipid solubility
• [D] Transfer rate and residence time at
  membrane hoe long the drug is present ouside absorption site

Question 6

Active diffusion

Answer 6

• Require transporter/carrier for the
  uptake of drug across cell membrane
• Low lipid solubility hydrophilic drugs
• Organic anion transporters and Organic cation transporters

Question 7

How do unionised drugs cross lipid membrane

Answer 7

• Crossing via passive diffusion
• Equalibrium between acid and base

Question 8

Factor affecting ionisation

Answer 8

• pH (i.e. concentration of H+ ions)
  – pKa of drug is the pH at which 50% of molecules are in each state

Question 9

Factors effecting GI absorption

Answer 9

• G.I. motility
• G.I. secretions & enzymes
• drug-food/supplement interactions

Question 10

Advantages of G. I absorption

Answer 10

• Large surface area for passive diffusion
  – Range of pH environments promote uptake of weak acids/bases
  – Richly vascularised (high blood supply)
  – Long tract and long dwell time
  – Some active transport ports
• Mainly absorbed in small intestine

Question 11

How well is the drug absorbed in the body

Answer 11

• Measure of proportion of
  dose absorbed, compared to I. V. dose
  F= AUC of oral/AUC of I.V
• Area under curve

Question 12

tmax

Answer 12

• Time required to reach
  maximum drug concentration in plasma
• tmax = 25 mins