Pharmacology Flashcards
define pharmacokinetics
what the body does to a drug (metabolism, absorption etc)
define pharmacodynamics
what a drug does to the body (i.e. drug-receptor interactions)
define a drug
a chemical substance of known structure which when administered to a living organism, has a biological effect
define a medicine
one or more drugs combined and administered with the intentions of achieving a therapeutic effect. not all drugs are medicines and not all medicines contain drugs. medicines have properties which treat disease or restore/correct physiological function by exerting a pharmacological, immunological or metabolic action or making a medical diagnosis
define therapeutics
the use of drugs to diagnose, prevent and treat illness
define formulations
how the active drug is combined with other substances to produce a medicine
define excipients
substances formulated alongside the drug such as bulking agents, preservatives or coatings
what are the three different names of a drug?
the chemical name (which describes the chemical structure)
the generic name (the class of drug to which a molecule belongs)
the proprietary/trade name (named by the manufacturer)
what would the ideal drug do?
- have the desired pharmacological action
- have acceptable or no side effects
- reach its target in the right concentration at the right time
- remain in sufficient concentration at the target for a sufficient time
- be rapidly and completely removed from the body after action
define ligand
a molecule that binds to a receptor. it can be exogenous (from outside), endogenous (from inside). it could be a drug, hormone or neurotransmitter and could act on one or many different receptors. they can also be synthetic or natural.
define receptor
a molecular target for a drug
define agonist
a molecule which ‘activates’ a receptor
define antagonist
a molecule which blocks or reduces agonist mediated responses (either by blocking the receptor or by reducing the effects of an agonist)
define target
a molecule, usually a protein, that is accessed by a drug to produce a therapeutic effect
define affinity
how well a ligand binds to a receptor, this can be strong or weak. very strong affinity may lead to permanent binding
how do drugs bind to receptors?
through steric (physical shape) interaction whereby the ligand fits into the receptor like a lock and key
what factors effect drug-receptor binding?
steric properties = the physical shape of the ligand and the receptor must be complementary
physiochemical properties = local charges across the receptor binding site and local charges on the corresponding site of the ligand must be opposing to have the strongest affinity.
target tissue - this doesn’t actually effect binding but the same drug acting on different tissues will produce different effects
how can pharmacogenetics effect responses to therapeutic drugs?
genes code for the production of proteins
genetic variation therefore leads to a variation in the proteins produced
proteins are the primary binding site for therapeutic drugs
so variations in proteins may change how drugs bind and the effect they have on the body.
what are the common targets for drug action?
most are proteins, common target proteins include
receptors
ion channels
carrier proteins
enzymes
what are the two different types of antagonist?
allosteric antagonists = these bind somewhere other than the ligand binding site but in doing so change the shape or charge of the ligand binding site meaning that the intended ligand can no longer bind to the receptor
orthostatic antagonists = these bind to and block the original ligand binding site, meaning that the intended ligand cannot bind.
what are G protein linked membrane receptors?
these are membrane receptors which cause a intracellular messenger cascade when a ligand binds to them, producing various effects including:
- altered cellular excitability
- modulation of other ion channels
- down regulation if G protein linked receptors
- long lasting impact on regulation of genes within the cell
how do drugs act on ion channels?
ion channels allow the movement of charged particles across a membrane, maintaining resting membrane potential. they are physical pores within the membrane but are selective as to what ions they allow through. drugs can either be:
blockers = drug sits within the ion channel, physically blocking it
modulators = drug binds to somewhere on the ion channel, changing its characteristics.
how do drugs act on carrier proteins?
carrier proteins facilitate transport of larger molecules across a membrane. disruption to carrier proteins results in the changing of membrane potential. drugs can be:
inhibitors = stop transport in carrier proteins
false substrates = act as the intended substrate to enter or change the action of carrier proteins.
how do drugs act on enzymes?
drugs interact with enzymes in many different ways. some common mechanisms include:
enzyme inhibitors = normal reaction is inhibited or blocked by the drug as the drugs are substrate analogues (same physical shape as the intended substrate) so they fit into the enzymes binding site
false substrates = drug binds to the enzyme and is broken down into abnormal metabolites
pro-drugs = an active drug is produced after enzymatic breakdown of the initial drug.
is any drug completely specific to one receptor?
no! side effects from drugs arise because although drugs may have specific target molecules, they are likely to bind to other receptors as well, causing a whole load of other effects. this is more likely when the drug is in the body in high concentrations.
what four processes determine a drugs time and duration of onset in the body?
absorption = process by which drug reaches systemic circulation
distribution = process by which drug reaches target area(s)
metabolism = the breaking down of a drug in the body, usually in the liver
excretion = removal of the drug, or its metabolites, from the body
what factors affect absorption of a drug?
- route of administration
- permeation (getting into the tissues of the body - must be in solution to do this)
what are the pros and cons of enternal (via gut) administration of drugs?
pros:
- low infection risk
- self-administration
cons:
- stomach is a harsh environment
- lots of the drug is lost to first pass metabolism
what are the pros and cons of injections?
pros:
- rapid bioavailability
- avoids first pass metabolism
cons:
- infection risks
- targeting risks
what are the different types of injection?
intravascular = directly into bloodstream
intramuscular = into skeletal muscle
subcutaneous
dermal
depot injection = for slow release formulation
what are the pros and cons of topical administration of drugs?
pros:
- local effects
- low systemic effects
- limited first pass metabolism risks
- low infection risk
cons
- long period of administration
- must be lipid soluble, small molecule and use a carrier molecule in order to permeate skin (this carrier molecule is usually an irritant to speed up absorption which isn’t great)
