What is a drug?

  • A medicine or other substance which has a physiological effect when ingested or otherwise introduced into the body

Over the counter label

Where is caffeine from?

  • Pharmacognosy
    • "the study of the physical, chemical, biochemical and biological properties of drugs, drug substances or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources."
  • Therapeutic use of plants/animals
  • As inspiration for derived drug mechanisms
  • BBC on "exploiting the ocean"

  • Over 60 plants contain caffeine
    • A secondary compound (not needed for survival)
    • found in tea leaves, kola nuts, guarana berries, or coffee beens
    • Doesn't damage the plant. Why? (hint, cell orgonelle usually associated with plants)
  • Caffeine is locked in vacuoles

Why do plants make caffeine?

  • A methylxanthine
    • Some evidence: dose-dependent inhibition of feeding associated with hyperactivity, tremors, and stunted growth
    • Less evidence: Psychoactive compounds promote proliferation

Leaves exposed to larvae


    • Liberation
    • Adsorption
    • Distribution
    • Metabolization
    • Excretion
  • From mug to urine


  • No-doze pills
  • Cup of coffee or tea

Adsorption & distribution

  • Around 3% of the caffeine your drink passes through without adsorption
  • Caffeine is fairly water solube
  • Easily enters the blood stream (hydrophobic)


  • Occurs in the liver

Caffeine pathway


  • Caffeine is able to pass through the cells of the kidneys
    • This is why hardly any caffeine is excreted in urine
    • Excretion of metabolites (like 1-methylxanthine) is more common


  • The effect of caffeine on the body
  • Adenosine receptors look out for adenosine
    • When adenosine binds, nerve cell activity decreases
    • Adenosine causes blood vessel dilation, potentially to aid sleep
  • Caffeine also binds to adenosine receptors
    • Blocking the effect of adenosine and increasing neuron firing
    • Also constricts blood vessels in the brain
  • Pituitary gland responds to increased neuron firing
    • Releases adrenaline
    • HR increases
  • Some of caffeines metabolites also appear to have similar effects as caffeine