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Drugs and The Brain – Understanding Addiction

  • Drugs come from plants either as by-products of them or developed chemically.
  • In the US, $150 billion is spent on legal pharmaceutical drugs.
  • All pharmaceutical drugs have at least three names.
    • chemical name of a drug is the organic chemistry chemical description of the molecule.  Most will never know or understand this name of a drug they are taking.
    • generic name of a drug is the official name of the drug.  It is still a detailed chemical name but much simpler.
    • brand name is for a specific formulation and manufacturer.
  • The big difference between the generic name and the brand name is that a generic name is public domain while a brand name is trademarked by the company that developed the drug.  The developing company gets to name the drug but it must be FDA approved.
  • One drug can be a painkiller, a controlled substance, a schedule II substance or just morphine.
  • Categories of psychoactive drugs are:
    • stimulants
    • hallucinogens
    • marijuana
    • depressants
    • opioids
    • psychotherapeutics
    • nicotine.
  • All drugs have defining characteristics.
  • The Physician’s Desk Reference has color photographs of most legally manufactured drugs; it also includes information like dose and potency.
  • The placebo effect is usually thought of in terms of a sugar or fake pill.
  • Many drugs effects are influenced by the users experiences, mood, how tired they are, in addition to other substances in the system, such as food to other drugs.
  • Dose-response refers to the correlation between the response and the quantity of drug administered.
    • The response may vary due to factors such as tolerance.
    • With a dose-response curve we hope to be able to answer a verity of questions; from what is an effective dose or a lethal dose.
  • Toxicity, in early animal studies, is measured in how many animals die as a result of taking the drug.  After more studies, the therapeutic index is set as LD50 / ED50.
  • The margin of safety is the difference between doses necessary for an intended effect and toxic unintended effects.
  • Potency refers to the amount of drug necessary to cause an effect, while toxicity is the capacity of a drug to upset or destroy normal body functions.
  • The forms and methods of taking drugs greatly effect how the drugs will interact with the users system.
    • Oral ingestion is the simplest way the drugs enter the body, but also the most complicated way to enter the bloodstream. Oral ingestion must make it through the acid in the stomach while avoiding neutralization by food and drink.  When the drug gets past the stomach it still has to go through the liver, as well as other organs.
    • Inhalation is when the drug is smoked or “huffed”.  Nicotine, marijuana, crack are most effective when delivered this way.   It is also rapidly absorbed due to all the capillaries in the lungs consequently moving quickly into the blood.  This is the fastest way to get psychoactive drugs into the system.
    • Injection put the drug into the system as well.
      • Intravenous injection puts the drugs right in the vein, so the onset of the effect of the drug is fast.  You can so put a high concentration of drugs in because it does not have to pass through a membrane.
      • Intramuscular injection puts the drug into the muscle and subcutaneous goes just under the skin.
    • Topical application is not used as often because many drugs are not absorbed effectively through the skin.
  • After drug administration, the body eliminates the drug through metabolism and excretion.
  • The drug will either leave the system or be changed so much that it will no longer have an effect on the body.
  • Prodrugs have been developed to start working only after they have been altered by the body.
  • The body has adaptive processes such as tolerance and dependence to protect against potential harm.
  • With drug disposition tolerance the more the drug is used the faster the metabolism or excretion.
  • Behavioral tolerance (conditioned tolerance) is when the behavior of the user changes even if the bio-chemical reaction in the body does not. There is strong evidence that tolerance effects are maximized when the drug-taking behavior occurs consistently in the same surroundings or under the same circumstances.


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