Chapter 4: PRINCIPLES OF PHARMACOLOGY

Question 1

What is psychopharmacology?

Answer 1

The study of the effects of drugs on the nervous system and behaviour.

Question 2

What are the two major aspects of drug influence?

Answer 2

• drug effects

- sites of action

Question 3

What are drug effects?

Answer 3

Observable changes in an individual’s physiology and/or behavior.

Question 4

What are sites of action?

Answer 4

The locations where drug molecules interact with molecules on or in cells to affect biochemical processes.

Question 5

What are pharmacokinetics?

Answer 5

The process by which drugs are absorbed, distributed within the body, metabolized, and excreted.

Question 6

What hapenns during absorption?

Answer 6

Drug is administered and absorbed through tissues. eg. intramuscular absorption

Question 7

What happens during distribution?

Answer 7

drug is distributed throughout body and blood.

Question 8

What happens during metabolism?

Answer 8

Drug is changed to an inactive form by enzymes, usually in liver.

Question 9

What happens during excretion?

Answer 9

Drug is excreted in urine by kidneys.

Question 10

What is the fastest route of administration of drugs?

Answer 10

• Intravenous injection (IV injection)

- Reaches brain in a few seconds

Question 11

What are the disadvantages of IV injection?

Answer 11

• required skills

- entire dose reaches bloodstream at once: if sensitive individual, little time to counteract the drug.

Question 12

How does intraperitoneal injection work?

Answer 12

-injected through the abdominal wall into the peritoneal cavity

Question 13

What is intramuscular injection (IM)?

Answer 13

intramuscular: directly into large muscle. drug absorbed into bloodstream through capillaries that supply muscle.

Question 14

What is subcutaneous injection?

Answer 14

-space beneath the skin

Question 15

What is the most common way of administering drugs?

Answer 15

• Oral administration
• Some drugs cannot be administered orally because they are destroyed by stomach acid or digestive enzymes. (ex: insulin)
• sublingual: under the tongue

Question 16

Does inhalation have rapid effects?

Answer 16

Yes because the route from the lungs to the brain is very short.

Question 17

What is topical administration?

Answer 17

• directly through the skin
• for steroid hormones, nicotine
• insufflation is a type of topical administration: contact with the nasal mucosa, rapid effect.

Question 18

Where are most of sites of action located ?

Answer 18

-on or in cells of the CNS

Question 19

What is the most important factor that determines at which rate the drug enters the nervous system?

Answer 19

-lipid solubility: the ability of fat-based molecules to pass through the cell membrane

Question 20

Why is the blood brain barrier not effective for drugs?

Answer 20

-blood-brain barrier is only for water-soluble molecules

Question 21

Is heroin or morphine more lipid soluble?

Answer 21

-Heroin is more lipid-soluble than morphine: IV injection of heroin will produce more rapid effects than morphine

Question 22

How is the drug metabolized and deactivated ?

Answer 22

-liver plays especially active role in enzymatic deactivation, but some deactivating enzymes also found in the blood, and brain.

Question 23

What happens in the case where the drugs become even more active during metabolisation?

Answer 23

• enzymes transform molecules of a drug into other forms that are biologically active.
• Transformed molecule can become even more active that the drug that is originally administered.
• Drug effects then have very long duration (ex: fluoxetine (prozac))

Question 24

What is a dose-response curve?

Answer 24

A graph of the magnitude of an effect of a drug as a function of the amount of drug administered.

Question 25

Why do we use the dose-response curve?

Answer 25

• Because drugs vary widely in their effectiveness
• The effects of a small dose of a relatively effective drug can equal or exceed the effects of larger amounts of a relatively ineffective drug

Question 26

What happens after the maximum effect point is reached?

Answer 26

Increasing the dose of the drug will not produce any more effect.

Question 27

What other effect than analgesia do opiates have?

Answer 27

-depress activity of neurons in the medulla that control heart rate and respiration.

Question 28

What is the margin of safety for opiates?

Answer 28

The distance between the dose-response curve for the analgesic effect of morphine and the dose-response curve for the depressive effect of morphine on respiration.

Question 29

What is the therapeutic index?

Answer 29

• The ratio between the dose that produces the desired effect in 50 percent of the animals and the dose that produces toxic effects in 50 percent of the animals.
• The lower the ratio the more careful you should be

Question 30

What are the two main reasons why drugs vary in their effectiveness?

Answer 30

• sites of action

- affinity of a drug with it’s site of action.

Question 31

What is the site of action of oxycodone?

Answer 31

-suppresses the activity of neurons in spinal cord and brain that are involved in pain perception

Question 32

What is the site of action of aspirin?

Answer 32

-reduces the production of a chemical involved in transmitting information form damaged tissue to pain-sensitive neurons.

Question 33

What is affinity?

Answer 33

• The readiness with which two molecules join together.
• high affinity: drug can be prescribed at relatively low dose
• low affinity: drug has to be prescribed at higher doses in order to function

Question 34

What’s the most desirable drug’s characteristics in terms of sites of action and affinity?

Answer 34

• high affinity for sites of action that produces desirable effects
• low affinity for sites of action that produce toxic effects.

Question 35

What is tolerance?

Answer 35

A decrease in the effectiveness of a drug that is administered repeatedly.

Question 36

What is sensitization?

Answer 36

An increase in the effectiveness of a drug that is administered repeatedly.

Question 37

What happens if someone who develops tolerance of a certain drug stop taking it suddenly?

Answer 37

-withdrawal symptoms:

opposite of drug effects (dysphoria, agitation…)

Question 38

What mechanisms of responsible for tolerance?

Answer 38

• Normally, most systems in body are regulated so that they stay at or near an optimal value
• Effects of drugs alter these systems for a prolonged time.
• Compensatory mechanisms begin to produce the opposite reaction.
• When stop taking the drug compensatory systems are not opposed by drug effects, and that’s what produces withdrawal symptoms.

Question 39

What is physical dependence ?

Answer 39

Compensatory changes following repeated use of a drug that results in withdrawal symptoms when the drug is no longer taken.

Question 40

What is receptor downregulation?

Answer 40

-Compensatory mechanism that involves a decrease of the binding of drugs with receptors.

Question 41

What are the two scenarios of downregulation?

Answer 41

• receptors become less sensitive to the drug do affinity of drug decreases
• receptors decrease in number

Question 42

What is the second compensatory mechanism other than receptor downregulation?

Answer 42

• involves the process that couples the receptors to ion channels in the membrane or to the production of second messengers.
• after prolonged stimulation of the receptors, one or more steps in the coupling process become less effective.

Question 43

What are the effects of barbiturates and do they cause tolerance or sensitization?

Answer 43

• cause sedation and also depress neurons that control respiration.
• the sedative effects show tolerance but the respiratory depression does not.

Question 44

What can repeated injections of cocaine produce?

Answer 44

• more and more likely to produce movement disorders and seizures
• euphoric effects of cocaine do not show sensitization

Question 45

What is a placebo?

Answer 45

An inert substance that is given to an organism in lieu of a physiologically active drug; used experimentally to control for the effects of mere administration of a drug.

Question 46

Is it correct to say that placebo have absolutely no effect because they are inert substances ?

Answer 46

• No it’s not correct
• If a person expects that a placebo can have a physiological or psychological effect, then it may actually produce that effect.

Question 47

What can placebo responses be the result of ?

Answer 47

• Changes in motivation
• Expectation
• Forms of learning (eg. classical conditioning)