CPT1: Absorption

Question 1

What is pharmacokinetics?

Answer 1

The study of the rate and extent of absorption. So the Absorption, distibution, metabolism and excretion of the drug

Question 2

What is pharmacodynamics?

Answer 2

What the drug does to the body

Question 3

What does pharmaokinetics tell us?

Answer 3

• What dose to give
• How often to give it
• Some drug interactions
• How to changre the dose in certain medical conditions

Question 4

What is absorption?

Answer 4

The movement of the drug from the site of admiinistation to the blood stream (across membrane)

Question 5

What are factors effecting the rate of absorption?

Answer 5

• Route of administration
• Dose
• Lipid solubility
• Weak acid/ base

Question 6

Give examples of different routes of administrations and their corresponding sites of absorption

Answer 6

1. IV - directly into venous blood
2. IM - muscles
3. Subcutaneous - into blood from skin layers
4. Epidural - epidural space
5. oral - mouth —> GI tract
6. Sublingual - under tounge into blood stream
7. buccal - oral muscosa to blood stream
8. intra-octular - eye
9. topical - skin
10. respiratory tract - nasal passage way or lungs

Question 7

What is ionisation?

Answer 7

The additional/ removal of an electron

process where an atom/ molecule aquired a +ve or -ve charge

Question 8

1. What is the henderson - hasselbalch equatoin?
2. Referring to the equation, when does pKa = pH?
3. what is the equation for pH?

Answer 8

1. pH = pka + log( [A-]/ [HA])
2. When A- = HA then pH = pKA and the drug is 50% ionised
3. pH = -log[H+]

Question 9

What is the equation used to determine %ionisation?

Answer 9

%ionisation = 100/ 1+ AL(pKa-pH)

Question 10

What are the mechanisms for crossing membranes?

Answer 10

• Passive
• Active
• Facilitated

Question 11

What are the requirements for passive diffusion?

Answer 11

• lipid solubilty
• water solubility

Question 12

Describe facilitated diffusion

Answer 12

A selective gate way allowing entery of one group of molecules

Question 13

Describe active transport

Answer 13

• Requires ATP
• Moves against conc gradient

Question 14

1. What are P-glycoproteins
2. What do they do?

Answer 14

1. Proteins with a carbohydrate attached
2. P-Glycoproteins sit on apical membranes and when substances cross the apical membrane the P-Glycoprotein causes it to be activately effluxed back into the gut. ATP dependent

Question 15

Where are G-glycoproteins located and what is there function there?

Answer 15

1. intestine - prevent absorption
2. liver - excretion into bile
3. kidney - excretion into urine
4. brain - prevent entery from blood to brain

Question 16

What drugs cause induction of P-glycoproteins

Answer 16

Rifampicin increases amount of P-glycoprotein in intestinal epithlelium - reduces absorption of other substances

Question 17

What drug causes inhibition of P-glycioproteins?

Answer 17

Verampamil saturates p-GP so other substances are absorbed more easily

Question 18

What is bioavailability?

Answer 18

Fraction of the original dose that reaches the systemic circulation in a chemically unaltered form

Question 19

What may be some causes of incomplete BA?

Answer 19

• Chemical degradation
• first pass metabolism
• faiulre to disintigrate/ dissolution
• failure of absorption or p-GP eflux

Question 20

what are some causes for failure of absorption

Answer 20

• Binding to other molecules
• Efflux due to P-GP
• too polar for passive diffusion

Question 21

What is plasma pH?

Answer 21

7.4