Lecture 7.6 (pharmacodynamics)

Question 1

What is pharmacodynamics?

Answer 1

Pharmacodynamics is concerned with the actions, interactions, and mechanisms of drug actions

Question 2

What may ensue if a patient receives a subcutaneous injection of 10 to 15mg of morphine sulfate?

Answer 2

analgesia,
sedation,
respiratory depression,
emesis (vomiting),
miosis (constriction of pupil),
suppression of the gastrointestinal tract, and
oliguria (deficient urine secretion)

Question 3

What is the relationship between pharmacokinetic and pharmacodynamic processes?

Answer 3

Drug conc at site of action as determined by the pharmacokinetic property of the drug —>
pharmacologic effect –> clincal response –> toxocity and efficacy –> utility of drug

Question 4

What is mode of action of a drug?

Answer 4

character of an effect produced by a drug

Question 5

What is the mode of action of morphine?

Answer 5

depressing function of the cerebral cortex, hypothalamus, and medullary center –>

decreasing pain perception (analgesia) + inducing
narcosis (heavy sedation) + depressing the cough
center (antitussive effect) + depressing the vomiting center + depressing the respiratory center

Question 6

What does the mechanism of action of a drugs refer to?

Answer 6

molecular and biochemical events leading to a response

Question 7

How does morphine cause respiratory depression?

Answer 7

by depressing the responsiveness of the respiratory center to carbon dioxide

Question 8

What are the 2 general classes that drugs may be divided into based on the basis of their mechanism of action?

Answer 8

1. structurally nonspecific
2. structurally specific

Question 9

What does the structure of a drug refer?

Answer 9

1. distribution of charge within a molecule
2. the spatial distribution of these potential binding domains

Question 10

What are characteristics of structurally nonspecific drugs?

Answer 10

◼ Mostly depressants
◼ Small (or even large) changes in structure have
negligible effect on activity
◼ Do not display stereoselectivity
◼ Drugs with widely different structure share a common
pharmacological action

Question 11

What is meant by ‘structurally nonspecific’ mechanism of action?

Answer 11

chemically dissimilar drugs depress biological activity by the same mechanism of action BUT
actions not related to their precise 3D structures

–> similar in function but not in structure

Question 12

Name 2 examples of a class of drugs that have ‘structurally nonspecific’ mode of action

Answer 12

1. General anesthesia:
   ◼ Inert gases ( xenon Xe)
   ◼ Halogenated hydrocarbons (halothane)
   ◼ Cyclic hydrocarbons (cyclopropane)
   ◼ Alcohols (ethanol)
   ◼ Oxides of nitrogen (nitrous oxide)
2. Antacids
   ◼ sodium bicarbonate
   ◼ aluminum hydroxide

Question 13

Name some chemicals/drugs for general anesthesia

Answer 13

◼ Inert gases ( xenon Xe)
◼ Halogenated hydrocarbons (halothane)
◼ Cyclic hydrocarbons (cyclopropane)
◼ Alcohols (ethanol)
◼ Oxides of nitrogen (nitrous oxide)

Question 14

Name some antacids

Answer 14

sodium bicarbonate and aluminum hydroxide

Question 15

What is meant by ‘structurally specific’ mechanism of action?

Answer 15

drugs exert their effects by interacting with specific receptors, a definite and strong relationship exists between the molecular structure of these compounds and their inherent pharmacologic properties.

Question 16

What are characteristics of structurally specific drugs?

Answer 16

◼ They produce their effects at low doses
◼ Minor changes in structure have major effects on
activity
◼ They commonly show stereo-selectivity

Question 17

Name a structurally specific drug that shows altered pharmacologic properties after modifications of its molecular structure

Answer 17

acetylcholine

*contains a quaternary nitrogen at one end of the molecule and an ester at the other end, separated by
a two-carbon linkage

Question 18

A drug produces its effects by interacting with a cellular component of the body such as:

Answer 18

◼ Receptors for neurotransmitters, autacoids or
hormones
◼ Enzymes
◼ Membranes

Question 19

What are autacoids?

Answer 19

biologically active substances that are produced locally by cells or tissues and act near their site of release

–> known as ‘local hormones’

Question 20

name an antagonist for the receptor that has morphine as its agonist

Answer 20

naloxone

Question 21

What is pharmacologic antagonism?

Answer 21

If two drugs, one an agonist and another an antagonist, bind to an identical receptor site, either producing or preventing an effect

Question 22

What is physiologic antagonism?

Answer 22

the drugs do not bind to the same receptor sites but
produce functionally opposite results

Question 23

Give an example of physiologic antagonism

Answer 23

Histamine produces vasodilation, whereas epinephrine (adrenaline) produces vasoconstriction

*different receptors

Question 24

Under what circumstances is physiologic antagonism used?

Answer 24

overcoming the toxicity of pharmacologic agents

Question 25

What is potentiation?

Answer 25

If the quantitative summation of the effects produced by two drugs is greater than the algebraic sum of the effects produced by either drug alone

Question 26

Give an example of potentiation.

Answer 26

When taken individually, diazepam, chlorpromazine, and alcohol all cause sedation. However, when alcohol is ingested along with either diazepam or chlorpromazine, pronounced CNS depression may arise and deaths have occurred

Question 27

How to calculate therapeutic index?

Answer 27

LD50/ED50 *LD50 = lethal doses to 50% of the population ED50 = median effective dose

Question 28

What index is used for quantitative measure of a drug's safety margin?

Answer 28

therapeutic index

Question 29

The higher the therapeutic index the ___________________.

Answer 29

safer the drug

Question 30

The lower the therapeutic index, the ___________________.

Answer 30

greater the possibility of toxicity

Question 31

What is the likely outcome if a drug shows a narrow therapeutic index.

Answer 31

means effective and toxic conc are similar --> Variation in patient response

Question 32

What is the significance of larger therapeutic index?

Answer 32

can have larger therapeutic window in terms of the dosage

Question 33

Explain 'synergism' as drug action

Answer 33

drug A only: effect produced drug B only: no effect produced drug A and B when administered together: effect produced is greater than that when only drug A is administered