Week 1 - Introduction Flashcards
Psychopharmacology
psychology + pharmacology
What is psychopharmacology?
The discipline that studies the effects of drugs on behaviour, cognitive functioning and emotions
What can knowing how a drug works aid in?
- prescribing the correct dosage of a medication
- predicting side effects
- predicting how 2 or more drugs may interact in the body
- helping to prevent and treat overdose
- treatment of substance use problems
- understanding of the neural basis of normal and pathological behaviour
Drugs have been used as part of?
religious and social ceremonies
In 1952 what did the antipsychotic effects of chlorpromazine on schizophrenia encourage?
- the development of new drugs & trials on previously abandoned drugs
- development of the formal discipline of psychopharmacology
- greater specificity of psychotropic drugs “a pill for every ill”
Chlorpromazine
Was the drug of choice for all mental diseases from 1952-1954.
Anxiolytic agents - Meprobamate
- first anxiolytic
- used clinically from 1955
- became most popular drug to treat neuroses
Antidepressants & mood stabilisers
1957: iproniazide, widely used as an antidepressant - noted in TB patients
1957: tricyclic antidepressant was used
1959: lithium accepted as drug of choice for BPD
What did the development of new drugs stimulate?
Interest in relationships between drugs, brain chemistry & behaviour
Increasing technological advancement developed?
more specific drugs & identifying their effects on brain and nervous system
The Psychopharmacological Revolution
- New techniques to allow researchers to look at machinery and working of the brain - MRI, CAT, PET
- Psychotherapeutic drugs do not cure mental disorders or suppress symptoms in all individuals
Basic classifications of psychotropics
- stimulants
- anxiolytics
- sedative-hypnotics
- opiates
- antidepressants
- antipsychotics
What is a drug?
Any substance that alters physiology, mood, cognitions or behaviour or a nonfood, nonmechanical substance
psychoactive drug
induce psychological effects by altering normal biochemical reactions in the nervous system
Describing doses
- Milligrams: 1/1000 of a gram
- doses given in accordance to body weight
ED50
median effective dose; the dose effective in 50% of individuals tested
LD50
median lethal dose; the dose that will kill 50% of individuals tested
Therapeutic Index (TI)
= LD50/ED50
Potency
differences in the ED50 between drugs. The lower the ED50 the more potent the drug
Effectiveness
differences in the maximum effect that drugs will produce at any dose
Primary/main effect
intended treatment result
Side effect
unintended; may be harmful
Therapeutic window
range of blood concentrations of a medicine between dose that produces undesirable side effects (toxic level) and dose that has intended effect (therapeutic level)
Names of drugs
- chemical name
- generic name
- trade name
- street name
Chemical name
describes molecular structure of a drug in terms of chemical make-up (7-chlor-1)
Generic name
shorter, simpler name that is made up for a drug (diazepam)
Trade name
name given to a drug manufactured by a drug company. Patented by the drug company for a number of years (valium)
Street name
slang names given by community, usually in relation to recreational drug use (weed, crack)
Drug name examples
Class: antidepressant (SSRI)
Generic: fluoxetine, sertraline
Trade: Prozac, Zoloft
Pharmacokinetics
processes involved in the movement of a drug in the body - absorption; distribution; elimination
Enzymes
molecules that control a certain chemical reaction; help to break down/ metabolise drugs
Metabolism
the process of restructuring (breaking down) molecules; detoxification
Half-life
time taken for the body to eliminate half of a given blood level of a drug
Drug interactions
the effect 2 or more drugs have on each other
Antagonist
a drug that diminishes the effect of another drug
Additive effect
a drug that enhances effect of another drug
Superadditive effects/potentiation
a drug has a greater effect when taken with another drug than might be expected by simply combining their effect
Oral administration
per oral; drugs are swallowed (typically absorbed via digestive system)
Inhalation of gases
allows fast distribution of a drug through the body and to the brain
Inhalation of smoke
as per gases, but in smoke particles cannot be exhaled
Intranasal administration
inhalation of solids/powders
Parenteral routes: injection (subcutaneous)
drug is injected just under the skin - fairly slow & even in absorption
Parenteral routes: injection (intramuscular)
needle is inserted into the muscle, usually the upper arm or buttock in humans
Parenteral routes: injection (intraperitoneal)
needle inserted into the peritoneal cavity (sack containing the visceral organs)
Parenteral routes: injection (intravenous)
needle inserted into the vein and drug administered directly into the bloodstream
Parenteral routes: injection (intrathecal)
needle inserted between the base of the skull and the first vertebra (so it reaches cerebrospinal fluid)
Parenteral routes: injection (intracerebroventricular)
needle inserted into a cannula inserted into the ventricles of the brain (bypasses blood brain barrier)
Transdermal administration
drugs administered through the skin (nicotine patch)
Intrarectal administration
suppositories placed in the rectum & drug is absorbed into the bloodstream
Lipid bilayer - cell membrane
double layer of fat molecules - for a drug to be absorbed into the body is must be capable of passing through several cell membranes (lipid soluble)
Lipid solubility
drugs that are lipid soluble can pass through cell membranes easily but drugs that readily dissolve in fats tend to stay in fat and are less effective (slow release)
Ionization/ion trapping
when a drug is dissolved in fluid it becomes ionized. Ions are not lipid soluble - the more ionized a drug is the slower it is to pass through the cell membrane
Protein binding
some proteins are too large to pass through pores in capillaries - substances which attach themselves to these proteins may never get to site of action
Barriers: Placental barrier
substances a mother takes pass through the placental barrier to the fetus (high lipid soluble drugs cross more easily)
- 75-100% of mother’s drug concentration reaches fetus <5mins
Barriers: Blood-brain barrier
prevents non-lipid-soluble substances getting into brain
Large protein molecular transporters
- passive transport mechanism
- active transport mechanism
Passive transport mechanism
non-lipid-soluble substances attach themselves to carrier molecule that can pass across membranes or uses protein channel to pass through
active transport mechanism
only takes place in living membranes; uses energy; actively concentrates a substance on one side of a membrane
Factors & structures affecting excretion of a drug
- drug concentration and kidney function
- liver and enzyme function
How does kidney function work?
kidneys filter unwanted substances out of the blood in the form of urine - work best with high concentrations of drug and filter at a lower rate with low concentrations in the blood
How does liver and enzyme function work?
liver uses enzymes to break down toxic substances into less harmful substances - i.e. presence/availability of enzymes is important
enzyme induction
levels of an enzyme can be increased by prior exposure to a drug that uses that enzyme
enzyme depression
metabolism is depressed when 2 drugs that use the same enzyme are taken at the same time, or one blocks enzyme activity of other
enzymes and age
enzymes are not fully functional at birth; liver function is less efficient in the elderly
enzymes and species
levels of enzymes differ in different species
First-pass metabolism
any drug absorbed from the digestive system passes through the liver and undergoes some degree of metabolism before going to the heart - route of administration affects metabolism
More factors affecting metabolism
- mode of administration produces different time courses
- the effects of a drug change over time
- absorption and excretion functions work together to give the resultant effect over time
