Absorption Flashcards

idk

1
Q

Define

Pharmacokinetics

(2)

A

Study and characterization of drug: ADME, with the aid of mathematical models which allow data to be interpreted.

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2
Q

What is the difference between

pharmacokinetics and Pharmacodyanmics?

(2)

A

Pharmacokinetics: Effect of body on drug
Pharmacodynamics: Effect of drug on body

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3
Q

Explain

Clinical pharmacokinetics

(1)

A

The application of pharmacokientics in the safe and effective therepeutic managment of the patient.

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4
Q

Summarise

Pharmacokinetics, Pharmacodynamics, Pharmacotherapeutics

(3)

A
  1. Pharmacokientics: ADME
  2. Pharmacodynamics: drug/receptor interaction
  3. Pharmacotherapeutics: Drug effect/response
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5
Q

State how we can use

The pharmacokientic properties of a drug

(3)

A

Dose and frequency of drug
How to change dose in certain medical conditions
How some drug interactions occur

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6
Q

Define

Abosrption

(1)

A

Movement of drug from site pf administration, across membranes and into the bloodstream

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7
Q

Note the factors

Which affect the rate of absorption

Red doors like working

(4)

A
  1. Route of administration
  2. Dose (concentration)
  3. Lipid-solubility of the drug
  4. Weak organic acid/base drugs
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8
Q

Draw a table

with routes of administration and their site of absorption

(10)

A

Draw table

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9
Q

Most drugs are weak organic acids/bases, what does this tell us?

A
  1. Most drugs are hydrocarbon molecules, sucg as aspirin, vitamins.
  2. They undergo ionisaiton/dissociation
  3. The pH of the solution as well as the pKa of the drug will tell us if the drug is in an ionised or non-ionised state.
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10
Q

Henderson - Hasselbach equation

(5)

A

pH = pKa + log (A- / HA)

  • pH = -log(H+)
  • pKa - dissociation constant for the acid
  • A- -concentration of the conjugate base
  • HA - concentration of the acid
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11
Q

Define

Passive diffusion

A

Movement of molecules from a higher concentration to a lower concentration, down a concentration gradient not requiring energy

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12
Q

Requirements of

passive diffusion

A
  1. Water solubility - almost all drugs are sufficiently water soluble
  2. Lipid solubility - some drugs lack the necessary lipid solubility
  3. In practice, passive diffusion depends mainly on lipid solubility
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13
Q

Draw a table with

Which molecules are effieicnet/ineffieicent in passive diffusion?

5|3

A

draw a table

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14
Q

Define

facilitated diffusion

(1)

A

Selective gateway allows entry of one group of molecules, but excludes all others.

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15
Q

What is

active transport

(3)

A
  1. Structurally selective
  2. Requires energy
  3. Can operate against the concentration gradient
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16
Q

Specifity of modes of transport?

(2)

A
  • Pasive diffusion - non specific, anything lipid soluble
  • Faciliated diffusion & Active transport - structurally specific group of molecules
17
Q

What are

p-glycoproteins?

(4)

A

Proteins with carbohydrates attached

  1. found in the apical cell membrane (facing gut contents)
  2. Substances are absorbed, but then actively pumped back into the gut contents (efflux).
  3. ATP dependent
18
Q

Draw a table showing

Location of P-glycoproteins

(4)

A

draw a table

19
Q

State the purpose of

P-glycoproteins?

(1)

A

Gnereally a defense mechanism against foreign substances

20
Q

What is

p-glycoprotein mediated efflux

(1)

A

This is when substances are absorbed, but then activley pumped out into gut contents, decreasing their absorption

21
Q

Examples of substances where intestinal absorption is opposed by p-glycoprotein mediated efflux

(6)

A

Celiprolol - Beta blocker
Cyclosporin - immunosuppresant
dexamethasone - glucocorticoid
ivermectin - anthelmintic
verapamil antihypersensative
vincristine - cytotoxic

22
Q

What is

Induction of p-gp

answer with example

(2)

A

example Rifampicin increase the amount of P-gp in the instestinal epithelium. this reduces absorption of other substances

23
Q

What is

inhibition of p-gp

answer with example

(2)

A

example: Large enough doses of verapamil will saturate the p-gp. Other substances then absorbed more easily. Has been suggested as a means to increase absorption of problem molecules

24
Q

What is

bioavailability (F)

(2)

A

The fraction of a dose that reaches the systematic circulation in a chemically unaltered form
1. as percentage or decimal
2. has no units

25
Q

Causes of

Incomplete bioavailability

(4)

A
  1. Failure of disintegration or dissolution
  2. Chemical, enzymatic, or bacterial attack
  3. Failure of absorption and pGp efflux
  4. First pass metabolism in the gut wall/liver
26
Q

Causes of

failure in absorption

(3)

A
  1. Binding to other molecules in the gut content
  2. Too polar to udnergo passive diffusion
  3. p-gp efflux
27
Q

Explain the

Ionisation of weak acids

(1)

A

will ionise more as the pH of the solution increases (the solution becomes less acidic) and vice versa

28
Q

Explain the

Ionisation of weak bases

(1)

A

Will ionise less as the pH increases and vice versa

29
Q

Explain the

effect of ionisation on drug absorption

membranes

(1)

A

Ionised drugs become too polar to cross the lipophilic layer across membranes

30
Q

In practice

Acidic drugs absorption

where in the body

(3)

A

In practice, acidic drugs will be absorbed mostly in the small intestine, this is because the surface fo the small instestine has villi and microvilli which greatly increasse the surface area of absorption.

31
Q

In practice,

Talk about the absorption of basic drugs and where absorption occurs

(3)

A

A basic drug will not be absorbed in the stomach all since pH is too low. so all of the drug will be abosrbed in the small intestine where the drug is unionised and the surface area is large.

32
Q
A