Drugs and MedicinesDrugs and Medicines

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Health and the Human BodyHealth and the Human Body

The human body maintains an intricate balance of The human body maintains an intricate balance of thousands of chemical reactions.thousands of chemical reactions.

These systems must respond to constantly These systems must respond to constantly changing demands from the individual’s activities.changing demands from the individual’s activities.

These systems are subject to challenges from These systems are subject to challenges from defects and malfunctions resulting fromdefects and malfunctions resulting from– genetic abnormalities.genetic abnormalities.– environmental challenges.environmental challenges.– changes accumulated through age.changes accumulated through age.– attacks from microorganisms.attacks from microorganisms.

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Lines of DefenseLines of DefenseBarriers to prevent entryBarriers to prevent entry– SkinSkin– Mucous membranesMucous membranes– Closures and secretions of natural Closures and secretions of natural

openings: lips, eyelids etc.openings: lips, eyelids etc.

Defense against attack invadersDefense against attack invaders– White blood cells (Phagocytes)]White blood cells (Phagocytes)]– Blood clotting to prevent blood lossBlood clotting to prevent blood loss– Inflammatory response.Inflammatory response.

Immune systemImmune system– Antibodies.Antibodies.– Memory cells to enable the body to Memory cells to enable the body to

fight repeat invasions.fight repeat invasions.3

Origins of PharmacologyOrigins of Pharmacology

From earliest times people have From earliest times people have used natural substances such as used natural substances such as medicinal herbs tomedicinal herbs to

-- relieve pain -- relieve pain -- heal injuries-- heal injuries-- cure diseases-- cure diseases

Some Some folk remediesfolk remedies contained contained certain active ingredients that certain active ingredients that were of medicinal value.were of medicinal value.

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Examples of Folk Examples of Folk RemediesRemedies

Morphine Morphine – extracted from poppy used to treat extracted from poppy used to treat

pain in the 19pain in the 19thth century. century.

Salicylic acidSalicylic acid – extracted from willow bark an a extracted from willow bark an a

precursor to aspirin.precursor to aspirin.

Quinine Quinine – Used in South America to treat Used in South America to treat

malaria.malaria.

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Definition of a MedicineDefinition of a MedicineAny chemical substance that Any chemical substance that improves healthimproves health

– Alters a physiological stateAlters a physiological state– Alters mood or emotionsAlters mood or emotions– Alters incoming sensory sensationsAlters incoming sensory sensations

Sometimes it is difficult to determine Sometimes it is difficult to determine whether a drug has any medicinal whether a drug has any medicinal value.value.Use of drugs in some cases is Use of drugs in some cases is controversial.controversial.

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The Placebo EffectThe Placebo Effect

Healing is a complex interaction between Healing is a complex interaction between mind and body mind and body that is not entirely understood.that is not entirely understood.The The Placebo EffectPlacebo Effect

Merely taking any medicine may Merely taking any medicine may trigger responses in the body that trigger responses in the body that result in changes in the result in changes in the mental/emotional or physiological mental/emotional or physiological states of the person without having states of the person without having any medicinal action.any medicinal action.

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Methods of Administering Methods of Administering DrugsDrugs

Drugs must reach blood stream to be Drugs must reach blood stream to be transported to critical tissues.transported to critical tissues.The method of administration determines The method of administration determines rate at which the drug is absorbed in the rate at which the drug is absorbed in the blood.blood.Five common points of entry:Five common points of entry:

1.1. OralOral2.2. InhalationInhalation3.3. TopicalTopical4.4. InjectionInjection5.5. AnalAnal

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Methods of Administering Methods of Administering DrugsDrugs

Injection methodsInjection methods– IntradermalIntradermal Between layers of Between layers of

skinskin

– SubcutaneousSubcutaneous Under the skinUnder the skin

– IntramuscularIntramuscular In the muscleIn the muscle

– IntravenousIntravenous Directly in the veinDirectly 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.

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

Therapeutic Window

The range of a drug’s 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?

Risk to Benefit RatioRisk to Benefit Ratio

The prescribing physician must weigh the The prescribing physician must weigh the benefits from the use of a drug against the benefits from the use of a drug against the undesirable side effects when determining a undesirable side effects when determining a suitable level of risksuitable level of risk

The level of risk that is acceptable is related The level of risk that is acceptable is related to the severity and the degree to which the to the severity and the degree to which the condition is life threateningcondition is life threatening

Examples: Chemotherapy, Pain Killers etcExamples: Chemotherapy, Pain Killers etc

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ToleranceToleranceOver time the body adapts the Over time the body adapts the presence of a drugpresence of a drug

1.1. The person receiving the drug The person receiving the drug needs ever larger doses to achieve needs ever larger doses to achieve the original effect.the original effect.

2.2. Tolerance results in increased risks Tolerance results in increased risks of dependency/addictionof dependency/addiction

3.3. Increased risks of toxic levelsIncreased risks of toxic levels4.4. Possibility of immunity in anti-Possibility of immunity in anti-

bacterials.bacterials.

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Thalidomide --An Example of Thalidomide --An Example of Improper Drug ApprovalImproper Drug Approval

Developed in Germany in the Developed in Germany in the 1953. 1953. Used as a tranquilizer (1957-Used as a tranquilizer (1957-1962).1962).Prescribed to combat morning Prescribed to combat morning sickness in the early months of sickness in the early months of pregnancy.pregnancy.Marketed widely in Europe but Marketed widely in Europe but never approved by the FDA in the never approved by the FDA in the USA.USA.Caused major birth defects in Caused major birth defects in ABOUT 10,000 children whose ABOUT 10,000 children whose mothers had taken thalidomide.mothers had taken thalidomide.

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ThalidomideThalidomideThalidomide is both a tranquilizer and a teratogen Thalidomide is both a tranquilizer and a teratogen

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It is sometimes used to It is sometimes used to treat some symptoms treat some symptoms of Hansen’s disease. of Hansen’s disease. (Leprosy) (Leprosy)

Drug ClassificationDrug Classification

Drug CategoriesDrug Categories 1.1. AnalgesicsAnalgesics

2.2. AnestheticsAnesthetics

3.3. AntacidsAntacids

4.4. StimulantsStimulants

5.5. DepressantsDepressants

6.6. AntibacterialAntibacterial

7.7. AntiviralAntiviral

8.8. Mind Altering DrugsMind Altering Drugs

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Research, Development Research, Development and Drug Testingand Drug Testing

Development of new drugs is long and Development of new drugs is long and expensive processexpensive process

Several stages in development include:Several stages in development include:1.1. Isolation or chemical synthesisIsolation or chemical synthesis

2.2. Laboratory studiesLaboratory studies

3.3. Animal testing to determine LDAnimal testing to determine LD5050

4.4. Clinical testing to determine Clinical testing to determine effectivenesseffectiveness

5.5. Approval by the FDA for marketApproval by the FDA for market

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Research, Development and Research, Development and Drug TestingDrug Testing

The development of a new drug is a time The development of a new drug is a time consuming processconsuming processDetermination of the Determination of the Lethal Dose or LDLethal Dose or LD5050. . This is the concentration that will kill 50% This is the concentration that will kill 50% of the animals in a test sampleof the animals in a test sampleThe The Effective Dose or EDEffective Dose or ED5050. is the . is the concentration necessary to bring about a concentration necessary to bring about a noticeable effect in 50% of the test samplenoticeable effect in 50% of the test sampleThe The Therapeutic IndexTherapeutic Index is the ratio of is the ratio of

LDLD5050..

EDED5050..

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Clinical TrialsClinical Trials

All drugs that are approved for market must All drugs that are approved for market must be be clinically testedclinically tested multiple times multiple times

Most clinical tests are done on volunteers Most clinical tests are done on volunteers using a using a double blind studydouble blind study

Some of the volunteers receive a Some of the volunteers receive a placeboplacebo while others receive the therapeutic medicinewhile others receive the therapeutic medicine

Neither the researcher nor the participants Neither the researcher nor the participants know in advance who receives which know in advance who receives which

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Drug DevelopmentDrug DevelopmentAll medicines have some side effects All medicines have some side effects and the appropriate dosage must be and the appropriate dosage must be determined.determined.To determine the following must be To determine the following must be considered:considered:– Lethal Dose or LDLethal Dose or LD5050

– Effective Dose or EDEffective Dose or ED5050

– Therapeutic IndexTherapeutic Index– Toxic RangeToxic Range– Therapeutic LevelTherapeutic Level– Sub-therapeutic levelSub-therapeutic level

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ReviewReview

1.1. When defining drugs what are three When defining drugs what are three ways in which drugs affect the body?ways in which drugs affect the body?

2.2. Explain the following: Therapeutic Explain the following: Therapeutic index, tolerance, the placebo effect, index, tolerance, the placebo effect, effective dose, lethal dose.effective dose, lethal dose.

3.3. Outline the steps in bringing a drug to Outline the steps in bringing a drug to market.market.

4.4. What happened with the drug, What happened with the drug, thalidomide, that resulted in a major thalidomide, that resulted in a major drug catastrophe?drug catastrophe?

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