Pharmacodynamics

Question 1

Pharmacodynamics

Answer 1

-study of the mechanism of action of the drugs on the body

Question 2

Competitive antagonism

Answer 2

• can be reversed completely by increasing the dose of the antagonist drug
• competitive antagonists reduce the potency but not the efficacy of agonists
  e. g atropine at muscarinic receptors, propanolol at beta-adrenergic receptors

Question 3

Non-competitive antagonists

Answer 3

• alter receptor site in some way
• increasing the dose of the agonist drug can reverse the effects only partially
• non-competitive antagonism reduces both the potency and efficacy of agonists
• e.g ketamine and phencyclidine are non-competitive NMDA antagonists

Question 4

Irreversible antagonists

Answer 4

• bind irreversibly to the target site

- e.g most MAOIs

Question 5

Pharmacological antagonism

Answer 5

-refers to the opposing action of 2 molecules acting via the same receptors

Question 6

Physiological antagonism

Answer 6

opposing action of 2 molecules by acting via different receptors e.g acetylcholine vs adrenergic actions

Question 7

Chemical antagonism

Answer 7

opposing action of 2 molecules by acting via chemical reactions
not seen in psychotropics but heparin and protamine reaction is an example

Question 8

Potency

Answer 8

• refers to the amount of the drug needed to produce a particular effect compared to another standard drug with similar receptor profile
• potency is determined by:
• the proportion of the drug reaching the receptor
• the affinity for the receptor
• efficacy

Question 9

Affinity

Answer 9

• refers to the ability of the drug to bind to its appropriate receptor (affection)
• drugs that bind readily to a receptor are described as having high affinity for that receptor
• the higher the affinity the more receptor a drug occupies and the more potent the drug is

Question 10

Ionotropic receptors

Answer 10

-ligand gated ionic channels
-activity leads to rapid transient increase in membrane permeability to either positivve cations like sodium or calcium or negative anions like chlloride
-causes excitation or inhibition of the post-synaptic membrane
E.G nicotinic Acetylcholine receptors, GABA-A, glutamate receptors, serotonin 5HT3
-GABA A and benzos work on these- quick

Question 11

Metabotropic receptors

Answer 11

• produce slower response involving G-proteins which bind to the intracellular portion of the receptor and activate a second messenger
• altered second messenger levels result in changes to phosphorylation state of key proteins, making them active or inactive
  e. g Dopamine (D1-5), Noradrenaline, Serotonin 5HT1-7 (except 5-HT3), muscarinic acetylcholine receptors. opioid receptors (mu)
• most antipsychotics and antidepressants- slow

Question 12

Full agonists

Answer 12

produce a maximal response

Question 13

Partial agonists

Answer 13

• cannot elicit maximum response and are less effective than full agonists
• e.g aripirazole, buspirone and buprenorphine
• have a ceiling effect

Question 14

Inverse agonists

Answer 14

• agent that binds to the same receptor but produces the opposite pharmacological effect
• no drug actually works this way

Question 15

Antagonists

Answer 15

drugs that interact with receptors to interfere with their activation by neurotransmitter or other agonistic molecules

Question 16

Efficacy

Answer 16

-how well a drug produces the expected response