The Biology of How Drugs Work

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  • Created on: 05-11-15 18:13
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The biology of how drugs work:
Mode of action
How does the drug work in the body?
It refers to how a drug affects biochemistry and physiological functions
Drugs act by stimulating or depressing normal physiological functions
1­ Attach to the receptorsand have the same effect as a neurotransmitter (the drug will fit
into the receptor)
2­ Block the receptor so that neurotransmitters cannot fit into them (the drug will form a
barrier so that neurotransmitters cannot be received)
3­ Prevent the recycling of neurotransmitters so that they stay in the synapse and can
re-attach to receptor sites (excess neurotransmitters can be reabsorbed into the sending
neurone ­ lack of this leads to an excess of neurotransmitters which blocks the pathway in
the synapse)
Agonists (1) ­ A drug that mimics the effect of a neurotransmitter and increases
post-synaptic activity by stimulating post synaptic receptors (increases activity in the
receptors)
Antagonists (2+3) ­ A drug which limits the effect of a neurotransmitter and reduces
post-synaptic activity. This can be either by blocking post-synaptic receptors or preventing
the recycling and or release of neurotransmitters (decreases activity in the receptors)
Types of neurotransmitter:
Monoamines:
o Excitatory neurotransmitters (known as neuromodulators)
o Able to stimulate far away neurones
o Includes dopamine, noradrenaline, adrenaline and serotonin
o Increases activity by firing more neurotransmitters at the same time
Endorphins
o Inhibitory neurotransmitters
o Interact with receptors responsible for blocking pain and controlling emotion
o Natural painkillers
GABA
o Inhibitory neurotransmitter
o 40% of synapses have GABA receptors

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Most drugs will affect GABA
Psychoactive drugs:
Stimulants= increase activity
Depressants = decreases activity
Both act on the CNS (brain and spinal cord) and can cause a chemical dependency
EXAMPLE: COCAINE
Acts indirectly on dopamine (involved in brains reward pathway)
Blocks the dopamine reuptake pump
Dopamine remains active in the synapse
Continues to bind to the postsynaptic receptors
Does not allow the recycling of neurotransmitters
Withdrawal symptoms:
"A set of clinical symptoms that develops when there is a sudden drop in the blood
levels of…read more

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The role of enzymes ­ More enzymes are produced in the liver to break down the drug
molecules. The body becomes more efficient at removing the drug from the body and more
drug is needed to have the same effect.…read more

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