Pharmacodynamics: MECHANISMS OF DRUG ACTION

Question 1

Pharmacodynamics is derived from two Greek words:

Answer 1

PHARMAKON-Drug
DYNAMIKOS- force or power

Question 2

Pharmacodynamics is defined as the study of:

Answer 2

• Defined as the study of action of drugs- effects of drugs and dose-effect relationship.
It describes what a drug does to the body.
• It is modification of action of one drug by another drug.

Question 3

Pharmacodynamics involves:

Answer 3

Receptor binding(including receptor sensitivity)
Post-receptor effects
Chemical interactions

Question 4

Pharmacodynamics is the study of biochemical and physiological effects of drug and their mechanism of action at_____ level as well as ____ level.

Answer 4

Organ, cellular

Question 5

The STRENGTH and LENGTH of interaction of drugs with a biological structure(eg 3 examples) determines HOW QUICKLY THE DRUG INITIATES THE EFFECT AND HOW LONG THE EFFECT LASTS.
True/False

Answer 5

Receptor
Enzyme
Transporter

TRUE

Question 6

Penicillin molecule binds to bacterial enzyme, ______ and prevents ___ in the bacterial cell wall.

Answer 6

TRANSPEPTIDASE.
Cross links

Question 7

Large amounts of penicillin completely blocks the enzyme and in the presence of small amounts, the enzyme resumes its normal function.
True/False

Answer 7

TRUE
This shows that the interaction between penicillin and the enzymes depends on the amount of penicillin present.

Question 8

Factors such as:
Aging
Effects of other drugs
Disorders which can change receptor binding; decreasing receptor sensitivity or altering the level of binding proteins CANNOT affect a drug’s pharmacodynamics.
True/False

Answer 8

False . It can affect the drug’s pharmacodynamics.

Question 9

Examples of disorders which cause change in receptor binding:

Answer 9

Genetic mutations
Malnutrition
Thyrotoxicosis

Question 10

Concerning principles of drug action,
Drugs impart new functions on system, organ or cell and also alters the pace of ongoing activity.
True/False.

Answer 10

FALSE. Drugs DON’T impart new functions on any system, organ or cell but rather alters PACE of ongoing activity!
An exception to this are GENE-BASED DRUGS

Question 11

Basic types of drug action can be broadly grouped as:

Answer 11

STIMULATION
DEPRESSION
IRRITATION
REPLACEMENT
CYTOTOXIC ACTION

Question 12

______ is the SELECTIVE enhancement of the level of activity of specialized cells.

Answer 12

STIMULATION

Question 13

Examples of stimulation:

Answer 13

PILOCARPINE on salivary glands
ADRENALINE on the heart

Question 14

Define DEPRESSION:

Answer 14

It is the SELECTIVE diminution of activity of specialized cells.

Question 15

Examples of DEPRESSION:

Answer 15

Barbiturates on the CNS
Quinidine on the heart
Omeprazole on gastric secretion

Question 16

IRRITATION is applied to _____ cells (epithelium and Connective tissue). It results in a _____ and often noxious effect. Strong irritation results in inflammation, _____,_____ and consequently, _____

Answer 16

Non-specialized
Non-selective
Corrosion, Necrosis
Loss of function

Question 17

Examples of Irritation:

Answer 17

Bitters in salivary and gastric secretion

Question 18

______ the use of NATURAL METABOLITES, hormones or their congeners in deficiency states.

Answer 18

REPLACEMENT

Question 19

Examples of replacement:

Answer 19

Levodopa in Parkinson’s disease (levodopa is a precursor to dopamine)
Insulin in Diabetes Milletus

Question 20

Cytotoxic action involves selective cytotoxic action on cancer cells or invading organisms, attenuating them without significantly affecting the host cells.
True/False

Answer 20

True

Question 21

Examples of cytotoxic action:

Answer 21

Cyclophosphamide - chemotherapy drug
Zidovudine- antiretroviral drug
Penicillin- antibiotics

Question 22

Mechanism of Drug Action:

Answer 22

Physical mechanism
Chemical mechanism

Question 23

__________ is when the drug does not produce any chemical reaction or change in the cells of the body and the effect is only physical. Examples are:

Answer 23

Physical mechanism
Activated charcoal binds with poisons in the stomach
Mannitol as an osmotic diuretic( freely filtered but not reabsorbed)
Bulk laxatives eg Ispaghula

Question 24

Drugs that act by producing chemical reactions in the body uses _______ mechanism.

Answer 24

Chemical Mechanism

Question 25

Examples of chemical mechanisms:

Answer 25

•NAHCO3 as antacid •Dimercaprol, penicillamine, desferrioxamine as chelating agents •Pralidoxime as a choline esterase reactivator •Cholestyramine for sequestration of bile acids and cholesterol in the gut

Question 26

Examples of discrete target bio-molecule drugs interact with:

Answer 26

Enzymes Carrier molecules Ion channels Receptor

Question 27

Drug- enzyme interactions may take place as _______ or _______

Answer 27

Enzyme inactivation Enzyme inhibition

Question 28

Enzyme inhibition may either be:

Answer 28

Competitive inhibition Non-competitive inhibition

Question 29

ACE inhibitors eg captopril Reversible anticholinesterases eg neostigmine, physostigmine Allopurinol used to inhibit xanthine oxidase in gout are examples of NON-COMPETITVE INHIBITION. True/False

Answer 29

FALSE. They are examples of competitive inhibition

Question 30

Neostigmine and Physostigmine are referred to as:

Answer 30

REVERSIBLE CHOLINESTERASE INHIBITORS

Question 31

Mechanism of allopurinol?

Answer 31

Allopurinol prevents gout-inflammation due to build up of urate crystals in joints by inhibition of xanthine oxidase which coverts xanthine and hypoxanthine uric acid.

Question 32

In non-competitive inhibition, effects are prolonged. True/False

Answer 32

True

Question 33

Examples of non-competitive inhibition:

Answer 33

Irreversible anticholinesterases eg organophosphorus compounds- insecticides and war gases Aspirin inhibits cyclooxygenase enzyme and therefore prostaglandin synthesis MAO inhibitors uses to treat depression eg Imipramine (NB: Depression is associated with decrease in catecholamines eg adrenaline. Monoamine oxidase helps with degradation of catecholamines so a MAO inhibitor helps to inhibit the effect of MAO therefore can be used to treat depression). Proton pump inhibitors: omeprazole inhibiting H+/K+ ATPase in parietal cells of stomach

Question 34

Some drugs intefere with the flow of Ion through the channels. Some of the ions are:

Answer 34

Na+ K+ Ca2+ Cl-

Question 35

Sodium channel drugs are: They help in treatment of?

Answer 35

Quinidine- anti-arrhythmic drug Procainamide- anti-arrhythmic drug Local anesthetics Cardiac arrhythmias and as local anesthetic

Question 36

Calcium channel drugs: Useful in what conditions:

Answer 36

Nifedipine(hypertension and angina) Verapamil (angina, hypertension, tachycardia) Diltiazem(angina, hypertension,arrhythmia) Hypertension Arrhythmias

Question 37

Potassium channel drugs:

Answer 37

Amiodarone, Sulfonylureas Amiodarone used in treating arrhythmias

Question 38

Chloride channel drugs: Affect what receptor:

Answer 38

Benzodiazepines GABA A receptor

Question 39

Inhibition of choline carrier by ______

Answer 39

Hemicholium

Question 40

Inhibition of noradrenaline vesicular uptake by _____

Answer 40

Reserpine

Question 41

Inhibition of neuronal uptake of noradrenaline ______

Answer 41

Desipramine

Question 42

Inhibition of neuronal uptake of serotonin _____

Answer 42

Fluoxetine aka PROZAC

Question 43

Inhibition of weak acid(eg uric acid) carrier by drugs _______

Answer 43

Probenecid which prevents uric acid tubular reabsorption thus enhancing its excretion

Question 44

_______ are regulatory macromolecular proteins.

Answer 44

Drug receptors

Question 45

_______ is an agent which activates a receptor to produce an effect similar to the physiological signal molecule. Example:

Answer 45

AGONIST Acetylcholine Noradrenaline Adrenaline

Question 46

______ are agents which prevents the action of an agonist on a receptor but does not have any effect of its own. Example:

Answer 46

Antagonist Atropine ( competitive antagonist of acetylcholine) Scopalamine(antimuscarinic) Phenoxybenzamine(non- competitive antagonist of noradrenaline)

Question 47

_____ is an agent which activates a receptor to produce submaximal effect, but antagonizes the effect of a fill agonist.

Answer 47

Partial agonist

Question 48

_____ is an agent which activates a receptor to produce an effect in the opposite direction of that of the agonist. Example:

Answer 48

INVERSE AGONIST Beta carbolines

Question 49

What is a ligand? Give examples

Answer 49

A ligand is any molecule which attaches selectively to particular receptors or sites. Ach, Noradrenaline, adrenaline, glutamate, aspartate and GABA

Question 50

Affinity is defined as the ____ by which a ligand binds to its receptor.

Answer 50

Tenacity

Question 51

Some drugs possess affinity but NOT efficacy. True/False

Answer 51

True

Question 52

The capacity to induce functional change in the receptor in a way that produces an effect is ______

Answer 52

Intrinsic Activity

Question 53

For agonist: Affinity + IA = ?

Answer 53

1

Question 54

For Antagonist: Affinity + IA = ?

Answer 54

0

Question 55

For Partial Agonist: Affinity + IA = ?

Answer 55

Between 0 and 1

Question 56

For Inverse agonist: Affinity + IA = ?

Answer 56

Between 0 and -1

Question 57

Two essential functions of receptor:

Answer 57

Recognition of specific ligand molecule Transduction of signal into response

Question 58

Receptors have two domains, namely:

Answer 58

Ligand binding domain Effectors domain(undergoes conformational change)