Psychobiology: Psychopharmacology, WEEK 6 Flashcards
1
Q
What is Psychopharmacology?
A
- Studying interaction between psychoactive drugs and the body
2
Q
What do psychoactive (psychotropic) drugs do?
A
- Alter neurotransmission
- Affect mood or behaviour
- Effective in managing psychological problems
- Aren’t naturally in the body, come from plants or synthesised from labs
3
Q
Why do we study psychopharmacology?
A
- Tells us something about how the brain works;
1. Role of specific transmitters and receptors in psychological processes > e.g: if we know a drug alters serotonin neurotransmission, we can see the effect of the drug on behaviour + infer role of serotonin in the behaviour
2. Causes of psychiatric illness > changes in brain functions which underlie psychiatric disorder > could develop better treatment - Helps us understand and deal with problematic drug use > wider social implications: concerns with health consequences of drugs + controversy over drug usage in psychiatry
- Education allows responsible assessment of costs/benefits of drug use in society > are certain drugs more helpful to our health or less.
4
Q
What does pharmacokinetics look at?
A
- Route of administration> how drugs get into the body
- Absorption/distribution> how drugs move through the body
- Metabolism > how drugs are transformed by the body
- Elimination/excretion > how drugs are removed from the body
5
Q
Routes of administration
A
- Drugs need to get into the bloodstream to have impact
- Oral/Ingestion
- Rectal
- Other mucous membranes : sublingual, buccal + nasal
- Transdermal
- Inhalation
- Injection (Intravenous, Intramuscular and subcutaneous)
6
Q
Routes of administration: Oral
Advantage + Disadvantage
A
- Oral/Ingestion: Most commonly used, comes in form of tablet or capsules > dissolves in stomach, passes into intestines where it gets to bloodstream via intestinal membrane
- Adv: It is convenient (can take it at any place without needing extra instruments) + Cheap and easy access
- Dis: Absorption is slow so shouldn’t be used in emergencies + could cause gastric irritation
7
Q
Routes of administration: Rectal
Advantage + Disadvantage
A
Rectal: Drugs in solid forms such as suppositories or in liquid forms are given by this route (mainly used on old patients) > some drugs can’t be ingested as it induces vomiting or get dissolved by acids in stomach so can’t reach bloodstream > use suppository like laxatives
- Adv: This route is preferred in unconscious or uncooperative patients + avoids nausea or vomiting
- Dis: Usually not accepted by patients + is invasive
8
Q
Routes of administration: Other mucous membrane
Advantage + Disadvantage
A
- Sublingual = under tongue, Buccal = cheek + nasal = nose>drug can get into bloodstream via other membranes
- E.G: sublingual: tablets placed under the tongue or between cheeks. The drug has to be lipid soluble and small
- Adv: Rapid absorption of drug + enters stream directly
- Dis: Might irritate mucous membrane
9
Q
Routes of administration: Transdermal
Advantage + Disadvantage
A
- Enters bloodstream via skin using patches containing drugs > drug gets released slowly over a period of time > e.g nicotine patch
- Adv: Steady intakes, avoids overdose
- Dis: shouldn’t be used in emergencies
10
Q
Routes of administration: Inhalation
Advantage + Disadvantage
A
- Inhaling via smoking + which takes drugs in quickly to the lungs > lungs have rich blood supply so drugs enter stream quickly > e.g: tobacco
- Adv: Effects are felt quickly as they absorb fast
- Dis: can irritate airways + damage lungs
11
Q
Routes of administration: Injection
Advantage + Disadvantage
A
- Intravenous: direct administration into vein + lacks precise amount of drug inserted (D) > e.g anaesthetic
- Intramuscular: drugs injected directly to muscles (e.g: vaccines)
- Subcutaneous: drugs injected under skin (e.g: insulin)
- Intrav: + Very fast rate of absorption - is invasive
- Intram: + Can hold large amounts of the medication -can cause side effects such as pain, numbness
- Subc: + Slow absorption -limited in volume of drug administered + retention at the injection site can lead to side effects.
12
Q
Absorption
A
- How the drug gains access to the blood plasma
- Unless drug is directly put into the vein, the membrane acts as a barrier which drug has to pass > some drugs will pass easier than others
- Diffusion of drugs across lipid membranes is affected by various factors: lipid-soluble and small molecules drugs diffuse best + Un-ionized drug molecules are more lipid soluble
13
Q
Journey of the drug
A
- Drugs have no sense of direction + have access to receptors all over the body
- Drugs circulate throughout body in plasma then enter tissue sites
- Encounter receptors for which they have affinity > bind to them
- Pharmacological response
14
Q
Distribution
A
- Target for psychoactive drugs is the usually brain > but in blood plasma a drug will reach all parts of the body
- Some side effects of psychoactive drugs are due to binding at receptors outside the brain > these side effects can be both desirable + undesirable
- Some drugs are temporarily inactivated by being stored in fat or attached to blood plasma proteins
- blood brain barrier acts as a selective barrier to drug distribution > only allows some drugs to pass
- Brain capillaries are different to normal ones, they are surrounded by glial cells which blocks drug molecules entering > lipid soluble molecules can’t pass easily
15
Q
Metabolism
A
- Converts the drug chemically into another compound
Can be inert (inactive) or can be active or even more active - Mainly takes place in the liver as it contains enzymes that help metabolism
- Sometimes essential for the drug to be eliminated > if it is a fat soluble drugs, it needs to metabolise to a water molecule to be eliminated via urine
16
Q
Elimination
A
- Can be eliminated in many ways
1. Urine: via the Kidneys, Only possible for water-soluble compounds > Fat-soluble drugs may be metabolised to make them water-soluble
2. Breath: eliminated by breathing via lungs E.g. certain amount of alcohol gets eliminated by breathing out, releasing the drug
3. Sweat + hair: Often un-metabolised + can be eliminated via sweat in skin + could get reincorporated through hair > is why hair-analysis can be used for drug testing (e.g: cocaine)
17
Q
Time-course of drug
A
- Amount of effect of drug increases by absorption, delay effect at the start.
- Process of metabolism + elimination reduces drug concentration + effect wears off as drug concentration isn’t enough to maintain activity
18
Q
Drug half life
A
- Half life quantifies duration of action of a drug
Half life of drug is time taken for amount of drug in plasma to fall by 50% - Impacts how frequently a drug has to be taken
- If half life for a drug is short it will be taken more frequently as effect wears off too quick > if half life is long it wont be taken as frequently.
