Mechanism of drug action

Question 1

Mechanism of drug action can be through:

Answer 1

• Interaction with target biomolecule like: receptors , enzymes [stimulation or inhibition] or ion transport channels
• Chemical reaction inside the cell
• Physical reaction like Radiation to the cell
• Interfere with cell division ; anticancer drugs

Question 2

Chemical reactions can be:

Answer 2

• Neutralisation (Use antacid to lower stomach acidity)
• Cheleation: A chleator takes the drug and removes it from the body by forming a chelate [inactive, insoluble complex, excreted in intestines)

Question 3

Example of neutralisation:

Answer 3

Heparin + protamin

Question 4

Example of chleation

Answer 4

EDTA removes calcium

Question 5

Physcical properties can be:

Answer 5

• Adsorbtion
• Osmosis
• Physical mass
• Radiation

Question 6

Adsorbtion example:

Answer 6

Activated charcoal has pores that trap drugs. Treats toxicity and diarrhea

Question 7

Radiation example:

Answer 7

Iodine-131 treats thyroid dysfunction

Question 8

Osmosis example:

Answer 8

Mannitol is used as a diuretic to increase the osmotic pressure in the kidney tubules and increase urine output

Question 9

Physical mass example

Answer 9

Fibres (cellulose) forms bulk laxatives that increase bowel movements. Treats constipation

Question 10

Where can a drug interact with a biomolecule?

Answer 10

• Enzymes causing stimulation or inhibition
• Ion channels
• Transporters
• Receptors

Question 11

Receptor definition:

Answer 11

It is a chemo-sensitive cellular macromolecule found on the surface of the cell that reacts specifically with a ligand (drug, transmitter or hormone) to produce a biological response

Question 12

All drugs that can work on a receptor has …. to the receptor but not all have ……

Answer 12

AFFINITY …… EFFICACY

Question 13

Affinity definition and factors it depends on :

Answer 13

The ability of a drug to fit into a receptor to form a DR complex
It depends on size, shape, electrical charge and atomic composition of the drug

Question 14

Efficacy definition:

Answer 14

The ability of a DR complex to produce a maximum response. Also known as intrinsic activity

Question 15

Potency definition:

Answer 15

The dose of the drug that is required to produce certain effects

Question 16

Drug-Receptor bond can be:

Answer 16

• Covalent bond
• Ionic bond
• Van der Waals bonds

Question 17

Drug-Receptor covalent bond

Answer 17

Very strong, irreversible and the block ends by re-synthesis of new receptors

Question 18

Drug-Receptor ionic bond

Answer 18

Weaker than covalent, reversible and occur between oppositely charged ions

Question 19

Drug-Receptor Van der Waals bond

Answer 19

Very weak, occur if the drug molecule and the receptor has a complementary 3-d conformation

Question 20

Drug-receptor interactions can be:

Answer 20

• Agonist
• Partial agonist
• Inverse agonist
• Antagonist

Question 21

Agonist definition:

Answer 21

The agonist is a chemical that binds to a receptor to produce maximum biological response

Question 22

Inverse agonist definition

Answer 22

Drug that activate the receptor to produce effects opposite to the agonist

Question 23

Partial agonist definition:

Answer 23

Drug that activate receptor to pproduce sub-maximal effect (when present alone)
Acts as an antagonist in presense of the pure agonist

Question 24

Antagonist definition

Answer 24

Drug that blocks the action of the agonist

Question 25

Regulation of receptors:

Long use of agonist

Answer 25

Desensitization or refractoriness (tolerance) occurs due to internalization of receptors.
Causes down regulation
Beta-agonist in bronchial asthma
Levodopa in Parkinsonism

Question 26

Regulation of receptors:

Long use of antagonist

Answer 26

Supersensitivty due to poliferation of receptors, causes exagerated response
Causes up regulation
Beta-blockers in angina pectons