psychopharmacology - week 6 part 1

Question 1

psychoactive drugs are drugs which:

Answer 1

alter neurotransmission
affect mood/behaviour
effective in managing psychological problems
- not naturally present in body
- may be found in plants
- compounds synthesised in a chemical lab

Question 2

psychopharmacology

Answer 2

study of the interaction between psychoactive drugs and the body

Question 3

why learn about psychopharmacology

Answer 3

tells us something about how the brain works
- role of specific transmitters + receptors in psychological processes
- causes of psychiatric illness

helps us understand and deal with problematic drug use
- concerns w/ health conc. of drugs
- controversy over drug usage in psychiatry
- education allows responsible assessment of costs/benefits of drug use in society

Question 4

what is pharmacokinetics concerned with

Answer 4

route of administration
absorption/distribution
metabolism
elimination/excretion

Question 5

routes of administration

Answer 5

oral
rectal
sublingual
buccal
nasal
transdermal
inhalation
injection

Question 6

routes of administration - oral

Answer 6

ingestion
most common - dissolves in stomach - intestines - blood stream via intentional membrane

adv
- self administered
- pain free
- easy
dis
- not suitable for emergencies (slow action)
- gastric irritation
- some drugs destroyed by acid in stomach

examples: paracetamol, calpol

Question 7

routes of administration - rectal

Answer 7

common if unconscious

adv
- avoids nausea
- potentially only option if cannot take orally
- drug cannot be destroyed by enzymes
dis
- invasive
- uncomfortable (irritation of rectum)
- reduced SA may limit absorption

examples: laxatives, acetaminophen

Question 8

routes of administration - sublingual

Answer 8

tabs under tongue

adv
- rapid and easy absorption
- alternatives to tablet
- drug directly into blood
dis
- accidentally swallowed
- unpleasant taste
- may irritate mucous membrane

examples; oxytocin, nitroglycerin

Question 9

routes of administration - transdermal

Answer 9

patches on skin

adv
- less frequent drug use
- painfree self administration
- drug released at steady rate
dis
- potential for allergicc reactions

examples; nicotine patches, contraception, anti-nausea

Question 10

routes of administration - inhalation

Answer 10

adv
- quick effect - straight into lungs
- fewer doses required
- can be used for unconscious patients
dis
- can lead to further breathing issues
- special apparatus needed

examples; asthma medication, anaesthetics

Question 11

routes of administration - intravenous injection

Answer 11

in veins

adv
- quick and precise
- preferred method fro unconscious patients
- can control exactly how much drug
dis
- requires skill
- greater risk of infection
- can be painful
- can lead to inflammation of blood vessel (phlebitis)

examples; chemotherapy drugs, some antibiotics (meropenem)

Question 12

routes of administration - intramuscular injection

Answer 12

in muscles

adv
- absorption rapid
- can control exact vol.
- slow-releasing drugs are also given this way
dis
- requires skill
- nerve damage

Question 13

routes of administration - subcutaneous injection

Answer 13

under the skin

adv
- absorption slow + constant
- hygienic
dis
- might lead to abscess formation
- absorption limited blood flow

examples; insulin, adrenaline, norplant

Question 14

absorption

Answer 14

unless give IV drug must cross cell membranes before can get to blood plasma
diffusion of drugs across lipid membranes effected by
- qualities of drugs
–> lipid soluble and small diffuse best
–> unionized drug molecules are more lipid-soluble

Question 15

distribution

Answer 15

target for psychoactive drugs usually in brain
in blood plasma so reach all parts of body
side effects due to bindng at receptor outside of brain

some drugs are temporarily inactivated by storage in fat or attached to blood plasma proteins
- may prevent them reaching target sites

the blood brain barrier acts as a selective barrier to drug distribution
- glial cells –> large or non lipid soluble cannot enter (brain capillaries different from normal ones as they are protected)

Question 16

metabolism

Answer 16

converts the drug chemically into another compound
- can be inert
- can be active (more active)

mainly takes place in the liver
- contains enzymes that help metabolism

sometimes essential for drug to be eliminated

Question 17

elimination

Answer 17

different routes

urine
- via kidneys (main route)
- water soluble compounds
- fat-soluble drugs may be metabolised to make them water soluble

breath
- alcohol

sweat + hair
- often unmetabolised
- hair analysis (drug testing)

Question 18

what is the duration of a drug affected by?

Answer 18

the rate at which it is metabolised and eliminated from the body

Question 19

what does the route of administration effect

Answer 19

how much of the drug is absorbed and the onset of the effects

Question 20

how to psycoactive drugs achieve their effects

Answer 20

by interacting with receptor sites in the brain

Question 21

how do psychoactive drugs reach receptor sites

Answer 21

may enter the blood stream to be distributed around the body

Question 22

what does the effect of a drug depend on?

Answer 22

the amount avaliable at receptor sites

principle of drug action: drug effects related to drug dose

for most psychoactive drugs amount of drug at receptor = amount in blood plasma

Question 23

what does the onset of the drug depend on

Answer 23

factors relating to absoption
- the time taken to reach peak plasma levels affects the response of drugs

after peak levels reached the amount of drug reaching receptors is affected by distribution around the body, rate of metabolism and elimination
- most drugs distribute rapid
- main factor = time to detoxicfy drug for elimination
- metabolism to activate drug prolomgs drug action

Question 24

what is half life

Answer 24

a measure of the duration of action of the drug and is defined as the time taken for the levels in the plasma to fall by half

short half life = needs to be administered more frequently