1. Principle Targets Flashcards
Why do dentists need to understand drugs?
- to use and prescribe ratioanlly
- dental patients may already be taking drugs
- be up to date with pharmacology and therapeutics
- principals stay the same when individuals come and go
What is pharmacology?
- what the drug does to the body
- what the body does to the drug
Define ‘pharmacodynamics’
the effects of a drug on the body
What falls into pharmacodynamics?
- molecular interactions by which drugs exert their effect (targets for drug action, how drugs act at target, how drug produces action)
- influence of drug conc on magnitude of response (graph representation, therapeutic vs toxic effects)
What does pharmacodynamics let us do?
- determine appropriate dose range for patients
- compare effectiveness and safety of one drug to another
Define ‘pharmacokinetics’
what the body does to a drug
4 divisions of pharmacokinetics
- absorption
- distribution
- metabolism
- excretion
What does pharmacokinetics let us do?
- design and optimise treatment regiments for people based on route of administration, frequency of administration and duration of treatment
If a woman is itchy and sneezing, you diagnose hayfever. What questions arise for pharmaco kinetics or dynamics?
for dynamics
- why is the drug called antihistamine, where in nose does it work and is the nose the sole location of action?
For kinetics
- taken as a tablet so how does it get to nose, if symptoms continue, why does she have to take another
Histamine is released from … when triggered by …
- mast cells
- allergy
Why do you need to take an antihistamine every day to maintain effects?
- absorbed and excreted through kidneys
- conc of antihistamine reduced until another tablet taken
2 sources of drugs
- naturally occurring
- synthetic
Explain naturally occurring sources of drugs
- previously main source (plants)
- imp source of new drugs like taxanes - anti cancer agents in yew tree bark
Explain synthetic sources of drugs
- current main source
- can be totally synthetic or identical to naturally derived compounds e.g insulin (identical) or codeine (derived)
Define ‘biologics’
- naturally derived (natural within body) but synthetic products (can be generated outside body) e.g growth hormones or antibodies
2 ways drugs can interact with targets
- on shape (lock and key)
- charge distribution (type of bonds holding drug to target)
List bonds from weakest to strongest
- van der Waal’s
- hydrogen bonds
- ionic interactions
- covalent bonds
Explain Van der Waal’s forces
- shifting electron density in a molecules results in generation of a transient pos or neg charge
- react with transient areas of opposite charge in other molecules
Explain hydrogen bonds
- hydrogen atoms bonded to oxygen or nitrogen become more positively polarised
- these bond with more negatively polarised atoms e.g oxygen
Explain ionic bonds
- atoms with an excess of electrons (negatively charged)
- attract to atoms with a deficiency of electrons (positively charged)
Explain covalent bonds
two bonding atoms share elctrons
4 considerations taken when looking at drugs binding with targets. Which are about shape and which about charge?
- hydrophobicity (how much it likes water)
- ionisation of drug (pKa)
(above at charge) - conformation of target
- stereochemistry of drug molecule
(above are shape)
Most drugs are weak …
bases or acids
Most drugs are weak bases or acids. What does this mean for them binding?
- exist in ionised form
- how charged they are affects target site binding
- some target sites only bind un-ionised molecules, some prefer ionised molecules
4 targets for drug action
- receptors
- ion channels
- enzymes
- carrier molecules
Define ‘receptors’
targets for endogenous transmitters e.g neurotransmitters and hormones
Define ‘enzymes’
biological catalysts which facilitate biochemical reactions
Define ‘ion channels’
pores which span membranes to allow selective passage of ions
Define ‘carrier molecules’
transport ions and small organic molecules across cell membranes
Example of a receptor as a target for drug action
- B2 adrenoreceptor
- salbutamol
- for asthma
Example of an ion channel as a target for drug action
- voltage gated sodium channel
- lidocaine
- local anaesthetic
Example of an enzyme l as a target for drug action
- cyclooxygenase
- aspirin
- analgesic
Example of a carrier molecule as a target for drug action
- proton pump
- omeprazole
- anti-ulcer
3 drugs which act due to their physico-chemical properties
- antidotes
- antacids
- laxatives
How do antacids work?
- neutralise too much acid with alkali
Example of a substance in antacid
aluminium hydroxide
Antidotes are effective because … for example …
- adds the chemical product that’s missing in overdose
- acetylcysteine to treat paracetamol overdose
Example of a laxative and how it works
- lactulose
- osmotic so adds water to faeces
