11. Pharmacokinetics III

Question 1

Describe the Blood Brain Barrier

Answer 1

a physical membrane barrier between the brain and the rest of the body that’s hard for drugs to penetrate.

Question 2

Describe the Area postrema.

Answer 2

part of brain with no BBB capable of responding to drugs in plasma.

Question 3

Describe the characteristic that helps a drug pass the BBB

Answer 3

-Very lipid soluble drugs are better at getting past the BBB than low lipid soluble drugs.

Question 4

Describe why dopamine cant’t pass the BBB

Answer 4

it is polar

Question 5

Describe what drugs are used to get more dopamine to the brain

Answer 5

-Dopamine cant pass BBB as it is polar.

-Levodopa is a precursor for dopamine that is capable of accessing Active transporters to pass the BBB.

-Levodopa can be converted to dopamine peripherally as well so either a high dose or another drug will be needed.

-Carbidopa is polar so cant pass BBB but can inactivate dopa carboxylase leaving levodopa to pass the BBB and have its clinical effect.

Question 6

Describe metabolism

Answer 6

-Required for the elimination of lipid soluble drugs converting them to water soluble molecules which are much more readily eliminated from the body in urine.

-Metabolites are inactive therefore metabolism determines the duration of therapeutic effect.

-Has 2 phases

Question 7

Describe Phase 1 of metabolism

Answer 7

Phase 1 is a oxidation, reduction or hydrolysis where it introduces a OH group to the molecule occurs on either carbon, nitrogen or sulfur

Question 8

Describe phase 2 of metabolism

Answer 8

Phase 2 is a conjugation reaction where it forms a covalent bond between the OH group and an endogenous substrate.