The 'Five Rights'

  • Right drug
  • Right dose
  • Right time
  • Right route
  • Right patient
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Types of Pharmacology

Pharmocognosy = sources of drugs

Pharmacokinetics = absorption, distribution, metabolism and excretion of drugs in the body

Pharmacodynamics = using drugs to prevent/ treat disease

Toxicolgy = study of poisons and unwanted effects

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Pharmacognosy = the source of drugs

  • plant
  • animal
  • mineral
  • chemical (synthetic)
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Routes of Administration

  • oral
  • inhaler
  • patch
  • topical (applied to body surfaces; eyes, nose, vagina, skin...)
  • intramuscular
  • subcutaneous (beneath the skin)
  • suppositry (rectum)
  • intravenour (fastest route)
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Factors Affecting Drug Absorption

  • route of administration
  • ability of drug to dissolve
  • food/fluids already in the body
  • weight (body surface area)
  • status of absorptive surface
  • rate of blood flow to small intestine
  • lipid solubility (ability to dissolve in fat)
  • status of digestive system (old age/ poor system)
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Distribution of Drugs

  • transported by the blood stream
  • water/fat soluable (dissolves in)
  • areas of quick distrubution: liver, heart, kidneys, brain
  • areas of slow distribution: muscle, fat, skin
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'First Pass Effect'

  • When the liver removes a drug before it is available for use (when orally administered)
  • the liver may extensively metabolise a drug before it passes into the circulatory system (less effective?)
  • IV administration bypasses the liver - preventing the first pass effect

Intravenous (IV) is the fastest route of administration

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Danger of Drug Metabolism

Danger of delayed drug metabolism:

  • accumulation of drugs
  • prolonged action of drugs

= possible overdose or adverse reaction when mixing drugs

Danger of stimulated drug metabolism:

  • diminished pharmacologic effects (may not achieve desired effect/ too quick)
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Excretion of Drugs

Through the:

  • kindeys
  • liver
  • bowel

Enterohepatic circulation = circulation of drugs through the GI tract

Biliary excretion = initiated in the liver

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  • receptors are reactive sites on a cell which selectively bind with a drug creating a pharmacologic response

Affinity = how well a drug will fit with a receptor (better fit = better response)

Agonist = drug and receptor bind leadingto a pharmacologic response

Antagonist = prevent a substance binding to receptors (eg. Beta Blockers)

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Mechanism of Action of Drugs

  • effects depend on the cells or organ targeted by the drug
  • once the drug hits the 'site of action' it can modify how and the rate at which a cell/ tissue functions
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Enzyme Interaction

  • Enzymes catalyse nearly all reactions in a cell
  • drugs interact with enzymes to alter the response/effect
  • can 'fool' enzyme into binding to a drug instead of a target cell
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Non-specific Interaction Between Enzymes and Drugs

  • doesn't involve a receptor site or an alteration in enzyme function
  • main site of action is cell membrane
  • drug will interfere or chemically alter cell function/ process
  • final product - defect/cell death (eg. caner treatment/ antibiotics)

*sometimes not specific enough - e.g. could treat throat infection but cause an alteration in the bacteria of the vagina

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Types of Drug Effects

  • Theraputic effect = expected response
  • Side effect = unintended secondary effects (from harmless to serious)
  • Adverse effect = undesirable response
  • Toxic effect = developed after prolonged intake /impaired metabolism or excretion
  • Idiosyncratic reaction = unpredictable effects (differs per individual)
  • Allergic reaction = drug acts as antigen (bad) which triggers the body to release antibodies - can be mild-severe (eg. hives/itching)
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Pregnancy and Breastfeeding


  • drugs can cross the placenta
  • first trimester is the period of greatest danger for drug induced fetal defects
  • can affect growth and functional developments in second trimester
  • can affect labour/the neonnate

Breast Feeding

  • exposes bf infants to drugs consumed by mother
  • risk to benefit ratio must be considered
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