Drugs%20and%20Medicines

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Drugs and Medicines
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 individuals 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 improves health
• 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.
• 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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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
• 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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Effects of Medicine

• Therapeutic effect
• The intended physiological effect of the drug
• Side-effects (contraindications) physiological
  effects that are not intended.
• These often vary from drug to drug and even from
  patient to patient.

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The Dose

• Dosing regime the amount of drug in each dose
  and the frequency of its administration
• Must consider factors like age, sex and weight to
  determine the correct regime

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Therapeutic Window

• The range of a drugs concentration in the blood
• Dosing determines the range
• Below the therapeutic window the drug is
  ineffective
• Above the range toxic levels can occur with
  disastrous side effects
• Why might the method of administration be an
  important factor in determining a dosing regime?

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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
• The person receiving the drug needs ever larger
  doses to achieve the original effect.
• Tolerance results in increased risks of
  dependency/addiction
• Increased risks of toxic levels
• Possibility of immunity in anti-bacterials.

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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

• Thalidomide is both a tranquilizer and a
  teratogen

It is sometimes used to treat some symptoms of
Hansens disease. (Leprosy)
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Drug Classification

• Drug Categories
• Analgesics
• Anesthetics
• Antacids
• Stimulants
• Depressants
• Antibacterial
• Antiviral

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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
• 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 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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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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