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BMSC1212 Introduction to pharmacology > Distribution > Flashcards

Flashcards in Distribution Deck (27):
1

What is distribution?

The reversible movement of drugs from the systematic circulation to the cells and interstitial tissues

2

What do highly porous capillaries allow?

Paracellular diffusion

3

What does the penetration of drugs into cells depend on?

Molecular size, lipid solubility and degree of ionisation

4

Why may lipid solubility be important to a drug?

Some drug receptors are situation within cells

5

What is HMG CoA reductase

The enzyme inhibited by the statin group of drugs used to lower bloop lipids in the treatment of hyperlipidaemia

6

Why can insulin not cross the plasma membrane?

Too large (large molecular mass)

7

Why can atracurium not cross the plasma membrane?

Highly ionised

8

What is perfusion?

Blood flow

9

Where is onset of action slower?

Skin, fat and bone

10

What is the distribution of hydrophilic and large molecular weight drugs rate-limited by?

The permeability of the blood-tissue boundary

11

Why does anaesthetic thiopental have a very short duration of action?

Time-dependent redistribution into fat, depletion in the brain.

12

What is redistribution

The transfer of a drug from the brain, back into the blood and then into peripheral organs

13

How do polar drugs exit the blood brain barrier?

Carrier-mediated transport

14

How do large hydrophilic drugs exit the blood brain barrier?

Fenestrations

15

How can some drugs be pumped back into the lumen?

P-glycoprotein, situated on the luminal surface of the endothelial cell plasma membrane

16

Why is the CNS surrounded by a barrier?

Make it difficult for hydrophilic substances to penetrate, tight junctions do not allow paracellular diffusion

17

Give three examples of drugs which can penetrate the blood-brain barrier by carrier mediated transport

1. Salicyclic acid
2. Valproic acid
3. L-DOPA

18

How is L-DOPA transported into the brain?

By the L-system, transports large neutral amino acids

19

What is required in the brain to treat Parkinson's disease and why is this a problem?

Dopamine, cannot cross the blood brain barrier

20

What converts L-DOPA to dopamine and why is this a problem?

DOPA decaroboxylase, converts L-DOPA in the periphery, reducing the amount able to cross the BBB

21

What does carbidopa do?

Blocks DOPA decarboxylase, cannot cross the BBB, serves to increase peripheral L-DOPA levels and does not inhibit dopamine conversion in the brain.

22

What is the placenta?

A structure that separates foetal and maternal blood

23

How does the placenta behave?

Like a lipid membrane, acts as a metabolic barrier contains a variety of enzymes cyt p450s, dependent mono-oxygenases and monoamine oxidases to metabolise substrates.

24

What can bound drugs not do?

Exit the blood system due to the high molecular mass of the protein-drug complex.

25

What is the effect of aspirin on warfarin?

Increases the unbound concentration and enhances its pharmalogical effects

26

What is a sequestered drug?

one which has accumulated to a concentration higher than in blood or plasma.

27

What happens to highly lipid soluble drugs in adipose tissue?

Accumulates such that their concentration in this tissue is many times that in blood.