Principles of Pharmacology
How drugs work
How drugs work
This presentation explains how drugs
Most drugs act at a molecular level
where they mostly bind to proteins to
produce their therapeutic effect
How drugs work part I
Most drugs bind to proteins
There are thousands of different proteins in
the body
Performing thousands of different tasks
Thus there are potentially thousands of
different targets for drugs
Types of protein
There are four classes of protein that
are targeted by drugs
• receptors
• enzymes
• ion channels
• carrier proteins
Receptor proteins
Receptors are found on every cell in the body
Receptors are very popular targets for drugs
Drugs that bind to receptors include
• Beta blockers
• Salbutamol
• Morphine
Agonists and antagonists
Some drugs bind to receptors and produce the
same effect as the endogenous ligand
These are called AGONISTS
Some drugs bind to receptors and produce no
effect other than preventing the endogenous
ligand from binding
These are called ANTAGONISTS
Agonists and antagonists
Cell membrane interactions
Enzymes are complex proteins that take
part in biochemical reactions
Many drugs target enzymes and block
biochemical reactions
Enzyme targeting drugs include…
• ACE inhibitors
• Statins
How drugs act on enzymes
Ion channels
Ion channels allow ions to cross membranes
Neurological functions rely on ion channels
Many drugs block ion channels including…
• Local anaesthetics
• Anti-arrhythmics
• Benzodiazepines
Channel blocking drugs
Carrier proteins
Carrier proteins actively transport molecules
across membranes
They are popular targets for drugs including…
• SSRIs (prozac etc.)
• Tricyclic antidepressants
• Loop diuretics
Drugs acting on carrier proteins
Similar chemical structure leads
to similar function
Drugs work by mimicking the chemical structure of a
desired target molecule
Damaged and pain-causing cells produce large quantities
of an enzyme called cylooxygenase-2. This enzyme in turn
produces a chemical called prostaglandin, which sends a
message to the brain signaling that a specific part of the
body is in pain. The chemical also causes the injured area
to release fluids, causing it to swell or become inflamed.
ASA (Aspirin) adheres to the cylooxygenase-2 and
prevents it from producing prostaglandin. Acetaminophen
and ibuprofin also work as an antagonist blocking the
production of prostaglandins. As a result, some of the pain
signals do not reach the brain and less pain is felt. Also,
the inflammation is minimized due to the lack of
prostaglandin production.
Acetylsalicylic acid
“ASA” Aspirin
Caffeine – 1,3,7-trimethylxanthine, to give it its chemical name
– is a member of a group of naturally occurring substances
called methylxanthines.
These compounds are similar in structure to adenosines,
naturally occurring molecules in our bodies which aid the onset
of sleep. In its natural context, which is in tea and coffee
plants, caffeine can kill or paralyse insects and is thus an
effective natural pesticide.
Adenosine bonds to receptor cells in the brain to calm the
activity of the central nervous system, thus triggering
tiredness. There is also evidence to suggest that it decreases
blood flow in the brain. Caffeine molecules bind to these
receptor cells but have no active effect on the nervous system.
However by doing so they take the place of adenosine molecules
that could make a difference. This process is known as
"competitive inhibition" and effectively delays the onset of
fatigue, increases alertness and improves people's ability to
sustain attention. Agonist or Antagonist?
Due to the similarity in structure, the caffeine molecule can bind to
receptor proteins that would normally bind to an adenosine derived
molecule. These receptors produce chemicals which tell an organism it
is tired and needs to sleep.
Benzodiazepine receptors are also
affected by caffeine, these
receptors control feelings of panic
and anxiety in humans.

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