Download Drugs and Medicines

Drugs and Medicines
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Orgins 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
Salicyclic acid
– extracted from willow bark as 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 betwe
en 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
1. Subcutaneous
2. Intramuscular
3. Intraveneous
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Research, Development and
Drug Testing
Development of new drugs is long and
expensive process
Several stages in development include:
1. Isolation or chemical synthesis
2. Laboratory studies
3. Animal testing
4. Clinical testing
5. Approval by the FDA for market
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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.
Neither the researcher know in advance
who is receiving the therapeutic medicine
and who is receiving a placebo
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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
– Theraputic Level
– Subtheraputic 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. 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 (1957-1962)
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
Has two optical
isomers, one of
which is a
powerful
teratogen.
Used to treat
some symptoms
of Hansen’s
disease
(Leprosy)
Chiral
Carbon
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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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