•  Abstinence: The act of self-restraint when it comes to avoiding opioids.
  • Abstinence Syndrome: The set of withdrawal symptoms that develops when use of opioids is stopped.
  • Affinity: In this context, the word refers to the strength of the interaction between a receptor and a ligand, a molecule that binds to a receptor to form a complex. When two ligands exist with equal molar concentration, the ligand with a higher affinity will most often displace the other from a receptor, if the lower-affinity ligand is bound reversibly to the receptor.
  • Agonist: A chemical substance capable of binding to a receptor to induce a full or partial pharmacological response.
  • Antagonist: A compound that binds to a receptor to form a complex which does not illicit any response. Also refers to a drug that can counteract the effects of another drug.
  • Delta receptors: An opioid receptor that has enkephalins as its endogenous ligands. The term refers collectively to two subtypes of opioid receptors, delta-1 and delta-2.
  • Dynorphin: A class of opioid peptides that acts as a selective agonist for the kappa opioid receptors.Endorphins: Endogenous opioid polypeptides that act as selective agonist for the mu-opioid receptors. They resemble opiates in their ability to produce a state of well-being and pain relief.
  • Endomorphin: Two endogenous opioid peptides, endomorphin-1 and endomorphin-2. These function as mu-agonists with greater selectivity than beta-endorphin.
  • Enkephalin: One of three families of opioid peptides produced by the body. It functions as a selective agonist for delta-opioid receptors.
  • Full agonist: A chemical substance capable of binding to a receptor to induce a full pharmacological response.
  • Fully Synthetic Opioids: These fully synthesized drugs include fentanyl, tramadol and methadone.
  • Inverse agonist: Binds to the same receptor site as an agonist but produces an opposite pharmacological response.
  • Intrinsic activity: This term refers to the ability of a drug-receptor complex to illicit a functional response.Kappa receptors = Refers collectively to three subtypes of opioid receptors (kappa-1, kappa-2, kappa-3).
  • Ligand: Substance that binds to and forms a complex with a biomolecule.
  • MMT: Stands for methadone maintenance therapy. This medical treatment is used for some people suffering opioid dependence to help wean them from other drugs.
  • Mixed agonist-antagonist: A drug or receptor ligand that has pharmacological properties like agonists and antagonists at certain receptor sites. An example includes buprenorphine which is included in the opiate replacement drug Suboxone.
  • Morphinan: The chemical base of many psychoactive drugs including opioid analgesics and cough suppressants.Narcotic: Class of substances that can blunt the senses. Narcotics can be used to treat pain, induce sleep or as a sedative. In large quantities, narcotics can cause euphoria, stupor and coma. Regular, prolonged use can lead to dependence and addiction.
  • Natural Opiate: An alkaloid found in the resin of the opium poppy. Examples are morphine, codeine and thebaine.
  • Neurotransmitter: A chemical substance that transmits nerve impulses across a synapse.
  • Opiate: A drug that contains opium or any of its derivatives. Examples are heroin, morphine and oxycodone. Opiates have the potential to cause habituation.
  • Opioid: Refers to any synthetic narcotic that has opiate-like properties but is not an opium derivative. Also refers to any of a group of naturally occurring peptides that bind or produce other action at opiate receptor sites.Partial agonist: A compound which binds and activates a given receptor, but unlike a full agonist, illicits only a partial pharmacological response.
  • Pharmacophore: A group of atoms in the molecule of a drug that causes the drug’s action.Structure activity relationship (SAR): The relationship that exists between the chemical structure of a drug and its activity.
  • Selectivity: The degree to which a drug dose produces a desired effect in relation to adverse effects.Semi-synthetic opioids: Created from natural opiates which are morphine, codeine and thebaine. Semi-synthetic opioids include oxycodone, hydrocodone, oxymorphone and hydromorphone.