Drugs and Medicines
L. Scheffler
IB Chemistry 3-4
Lincoln High School
Version 1.05
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Health and the Human Body
The human body maintains an intricate balance of
thousands of chemical reactions.
These systems must respond to constantly changing
demands from the individual’s activities.
These systems are subject to challenges from
defects and malfunctions resulting from
– genetic abnormalities.
– environmental challenges.
– changes accumulated through age.
– attacks from microorganisms.
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Lines of Defense
Barriers to prevent entry
– Skin
– Mucous membranes
– Closures and secretions of natural openings: lips,
eyelids etc.
Defense against attack invaders
– White blood cells (Phagocytes)]
– Blood clotting to prevent blood loss
– Inflammatory response.
Immune system
– Antibodies.
– Memory cells to enable the body to fight repeat
invasions.
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Origins of Pharmacology
From earliest times people have used natural
substances such as medicinal herbs to
-- relieve pain
-- heal injuries
-- cure diseases
Some folk remedies contained certain active
ingredients that were of medicinal value.
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Examples of Folk Remedies
Morphine
– extracted from poppy used to treat
pain in the 19th century.
Salicylic acid
– extracted from willow bark an a precursor
to aspirin.
Quinine
– Used in South America to treat malaria.
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Definition of a Medicine
Any chemical substance that
– Alters a physiological state
– Alters mood or emotions
– Alters incoming sensory sensations
Sometimes it is difficult to determine
whether a drug has any medicinal value.
The legitimate purpose of a drug is
usually to improve health.
Use of drugs in some cases is
controversial.
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The Placebo Effect
Healing is a complex interaction between
mind and body that is not entirely
understood.
The Placebo Effect
Merely taking any medicine may
trigger responses in the body that
result in changes in the
mental/emotional or physiological
states of the person without having
any medicinal action.
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Drugs and Medicines
Access to drugs and medicines is
controlled in most countries but the
definition of what constitutes a drug
may vary.
Examples:
–Melatonin
–Codeine
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Methods of Administering Drugs
Drugs must reach blood stream to be
transported to critical tissues.
The method of administration determines
rate at which the drug is absorbed in the
blood.
Five common points of entry:
1.
2.
3.
4.
5.
Oral
Inhalation
Topical
Injection
Anal
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Methods of Administering Drugs
Injection methods
– Intradermal
Between layers of
skin
– Subcutaneous
Under the skin
– Intramuscular
In the muscle
– Intravenous
Directly in the vein
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Research, Development and
Drug Testing
Development of new drugs is long and
expensive process
Several stages in development include:
Isolation or chemical synthesis
Laboratory studies
Animal testing to determine LD50
Clinical testing to determine
effectiveness
5. Approval by the FDA for market
1.
2.
3.
4.
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Research, Development and
Drug Testing
The development of a new drug is a time
consuming process
Determination of the Lethal Dose or LD50.
This is the concentration that will kill 50% of
the animals in a test sample
The Effective Dose or ED50. is the
concentration necessary to bring about a
noticeable effect in 50% of the test sample
The Therapeutic Index is the ratio of
LD50.
ED50.
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Clinical Trials
All drugs that are approved for market must
be clinically tested multiple times
Most clinical tests are done on volunteers
using a double blind study
Some of the volunteers receive a placebo
while others receive the therapeutic medicine
Neither the researcher nor the participants
know in advance who receives which
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Drug Development
All medicines have some side effects and
the appropriate dosage must be
determined.
To determine the following must be
considered:
– Lethal Dose or LD50
– Effective Dose or ED50
– Therapeutic Index
– Toxic Range
– Therapeutic Level
– Sub-therapeutic level
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Contraindications or Side Effects
Contraindications are additional and often
undesirable effects that result from the use
of a particular drug to treat a particular
condition.
Side effects are somewhat relative
depending on the reason the drug is
prescribed
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Risk to Benefit Ratio
The prescribing physician must weigh the
benefits from the use of a drug against the
undesirable side effects when determining a
suitable level of risk
The level of risk that is acceptable is related
to the severity and the degree to which the
condition is life threatening
Examples: Chemotherapy, Pain Killers etc
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Tolerance
Over time the body adapts the
presence of a drug
1. The person receiving the drug
needs ever larger doses to achieve
the original effect.
2. Tolerance results in increased risks
of dependency/addiction
3. Increased risks of toxic levels
4. Possibility of immunity in antibacterials.
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Thalidomide --An Example of
Improper Drug Approval
Developed in Germany in the
1953.
Used as a tranquilizer (19571962).
Prescribed to combat morning
sickness in the early months of
pregnancy.
Marketed widely in Europe but
never approved by the FDA in the
USA.
Caused major birth defects in
ABOUT 10,000 children whose
mothers had taken thalidomide.
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Thalidomide
Thalidomide has
two optical isomers,
one of which is a
powerful teratogen.
Chiral
Carbon
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Thalidomide
Thalidomide is both a tranquilizer and a teratogen
It is sometimes used to
treat some symptoms
of Hansen’s disease.
(Leprosy)
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Drug Classification
Drug Categories
1. Depressants
2. Stimulants
3. Antacids
4. Analgesics
5. Antibacterial
6. Antiviral
7. Mind Altering Drugs
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Review
1. When defining drugs what are three ways
in which drugs affect the body?
2. Explain the following: Therapeutic index,
tolerance, the placebo effect, effective
dose, lethal dose.
3. Outline the steps in bringing a drug to
market.
4. What happened with the drug,
thalidomide, that resulted in a major drug
catastrophe?
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