12.3 Analgesics
http://www.nlm.nih.gov/medlinepl
us/druginformation.html
Describe and Explain the different
ways in which analgesics prevent
pain
Pain Receptor
• Nerves that transmit the pain
• Free nerve endings that transmit the pain
based on thermal/ mechanical/ chemical
stimuli
• Pain receptor generate an impulse
• Pain results from interaction between
various impulses arriving at the spinal cord
and the brain
Prostaglandins
• Injures tissues release
prostaglandin and leukotriene
• Make the pain receptors more
sensitive
Prostoglandin
• Prostaglandins have an extraordinarily
wide range of biological effects
• controlling blood pressure and controlling
inflammation.
• blood clotting, kidney function and the
reproductive system
• and are the subject of a great deal of
research to produce new drugs.
Analgesics
• Understanding how neurons work comes
from study of membrane potential
• (i.e. the difference in electrical charge
between inside and outside of the
neuron);
• To record a membrane potential two
electrodes are needed: intracellular
and extracellular
•
Aspirin
Analgesics: relives pain
Mild : aspirin, acetaminophen( metabolic
byproduct of phenacetin)
-same as Tylenol, Paracetamol,
ibuprofen ( sold as Actiprofen, Advil, MortrinIB,
Medipren)
NSAIDS ( non-steroidal anti-inflammatory drugs)
Mild analgesics : non addictive
Mild Analgesics
• Block the enzyme –cyclooxygenase / controlled
synthesis of prostaglandins
• responsible for constricting of blood vessels
• increase the body temperature
• Direct effect on hypothalamus / body’s heat
regulating center / produces fever
• Cause swelling and pain / increase the
permeability of capillaries, allowing water to
pass out into nearby tissues
Mild Analgesics
• Lower the concentration of prostaglandins
• Reduce fever
• And inflammation
Endorphins and enkephalin
Enkaphalin
Endorphin
• Endorphin comes from the words
endogenous morphine.
• Endogenous means developing from
within.
• Endorphins are similar to the narcotic
morphine in their functions,.
• They occur naturally in the brain and
bloodstream.
Endorphin
• a group of peptide hormones that
bind to opiate receptors
• and are found mainly in the brain.
• Endorphins reduce the sensation
of pain and affect emotions.
Endorphin
• Russian scientists claim a beating
on the buttocks with a strong
cane is the perfect way to cure
everything from depression to
alcoholism by releasing the
body's natural "happy chemicals"
known as endorphins.
B3.2 Salicylic acid
• Describe the uses of derivatives of
salicylic acid as mild analgesics and
• compare the advantages and
disadvantages of using
• aspirin and paracetamol
• acetaminophen)
Salicylic acid /Acetyl salicylic acid
Salicylic Acid
• Antipyretic / fever reducer
• Mild analgesic / pain killer
• Strong/ damages the membrane lining the
mouth, esophagus and stomach
• Chemically modified to sodium salt of acid
• Less unpleasant, but turn to acid in the
stomach
• acetyl salicylic acid / reduce acidity/ non
irritating /taken orally
Synthesis
Hydrolysis
+
H2O
CH3COOH
ASA
• Prodrug :less active form of drug
that is converted to the active
form of drug after administration
• Sometimes sold as sodium salt
of ASA / Alka Seltzer. / ionic
bonding / dissolves in water
ASA
• The presence of OH and COOH
group on benzene ring makes
salicylic acid as strong acid
• Other derivatives are insoluble
due the presence of aromatic ring
Uses of the Derivatives of salicylic
acid ( Miracle drug)
• Antipyretic: reduces fever
• Anti-inflammatory
• Anti-platelet agent / prevent abnormal
blood clotting , anti clotting agent
• (inhibits the production of prostaglandins)
• Mild analgesic
– minor aches/pains, headaches, sunburn,
arthritis
Disadvantages of ASA
• Stomach upset due to acidity in aq. Solution
• Gastrointestinal bleeding following use of
alcohol
• 0.5% who take ASA (and 3-5% asthmatic) are
allergic to ASA leading to skin rashes,
respiratory difficulty
• Accidental poisoning in infants
• Development of Reye’s syndrome/ liver and
brain disorder can result in coma, brain damage
and death ( children who took ASA for chicken
pox symptoms)
Base hydrolysis
Pain reliever
Aspirin Substitute
•
•
•
•
•
•
Paracetomol
Active ingredient in many OTC
USES:
Anti –pyretic / reduces fever
Analgesics reduce pain
Does not upset stomach
Acetaminophen
• NOT an anti-inflammatory
• Can cause blood disorder and kidney
damage
• Over dose can cause liver damage, brain
damage, coma and even death
Acetaminophen
Phenacetin
Ibuprofen
• (2-[4-(2-Methylpropyl)phenyl]propanoic Acid,
Isobutylphenylpropionic Acid)
• Same as ASA but fewer stomach problems
• Anti-inflammatory
• Wide margin of safety,
• Lower effective dose
• Large doses /kidney problems
www.wcer.wisc.edu/.../Spr2000/esselman/IBU
b.html
2-(4-Isobutyl-phenyl)-propionic
acid
• ibuprofen
Opium
Strong Analgesics
• Relief of very severe pain,
• include narcotics : heroin, codeine,
morphine
• Addictive
• Controlled substances
Heroin
Strong
Analgesics
Local anesthetics
• Pain killers in localizes areas
• Lidocaine and procaine (Novocaine)
• Used in dentistry
Novocaine
• t is the first injectable local anesthetic to
be synthesized,
• commonly known as Novocain.
• The German Chemist, Alfred Einhorn,
developed it in 1904.
• Procaine is the precursor to cocaine.
• Procaine works to anesthetize a patient for
about 15 minutes. To prolong anesthesia
epinephrine is added as a vasoconstrictor.
Procaine/Cocaine
• Cocaine blocks Na+ passage
through the axon cell membrane
and
• inhibits the reuptake of Dopamine
and Serotonin
• resulting in psycho-stimulation.
Procaine
• Procaine blocks nerve conductance
via inhibiting Na+ at the membrane,
• thus no psycho-stimulation.
• Both reactions are brief.
• Drug Interactions?
• Procaine is thought to reduce the effects of
sulfonamide antibiotics.
• How is this medication administered?
• Oral injection.
Lidocaine
General Anesthetics B9-447
SEROTONIN,
happy neurotransmitter.
• 5-hydoxytryptamine, is naturally produced
in the pineal gland, which lies at the centre
of our brain.
• “It is essential to numerous body function
including appetite control, sleep, memory
and learning, temperature regulation,
mood, behavior, cardiovascular function,
muscle contraction, endocrine regulation
and depression.
DOPAMINE,
• 4-(2-aminoethyl)benzene-1,2-idol, is
produced in several areas of the brain
including the substantia nigra.
• It is central to movement coordination,
cognitive functions (by mediating signal
transduction in the frontal lobe thus
affecting memory, attention, and problemsolving in particular), latent inhibition and
creative drive.
Dopamine
• Its release is stimulated by naturally
rewarding experiences
• such as happy foods (bananas!), drugs,