Summary and Key Points

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In order to understand the mechanisms and treatment of opioid dependence, it is important to first understand the pharmacological properties of opioids. Buprenorphine's effectiveness as a treatment for this condition rests largely on the unique characteristics of its pharmacological profile.

  • An opioid is a neurotransmitter analog that activates opioid receptors within the body.
  • Opioid receptors can also be activated by endogenously produced chemicals, known as opioid peptides.
  • There are three categories of opioids: natural (those produced by plants), semi-synthetic (those chemically derived from natural opioids) and synthetic (those manufactured entirely synthetically).
  • Opioids are typically used for analgesia, but also have applications for cough suppression and diarrhea.
  • There are three types of opioid receptors: mu, kappa and delta. Of these, the mu-opioid receptor is typically of central focus in terms of dependence.
  • An opioid can be either a full agonist, a partial agonist or an antagonist of an opioid receptor. An agonist activates the receptor, while an antagonist blocks the receptor from activation.
  • Partial agonists activate (partially) their respective opioid receptor and can also block other agonists from binding.
  • There are two types of opioid antagonists. Neutral antagonists simply block the action of agonists by occupying the opioid receptor site. Inverse agonists, however, also suppress the activity of the receptor.
  • Partial agonists are safer than full agonists, as overdose is less likely and less likely to be life-threatening. This is due to a lower "ceiling of effect" on the dose-response curve.
  • Methadone, introduced during the 1960's, was the first opioid used in maintenance treatment. However, it has several drawbacks in terms of safety and efficacy.
  • Buprenorphine, recently approved for the treatment of opioid dependence, has properties of a partial agonist at the mu receptor and a full antagonist at the kappa receptor.
  • Suboxone is the most prevalent buprenorphine formulation, and contains buprenorphine and the opioid antagonist naloxone in a 4:1 ratio. The naloxone discourages users from injecting the drug to achieve the "rush" sought after by illicit users.
  • Continued use of opioids can lead to tolerance (the need for more of the drug to achieve the same effects) as well as dependence (the need to continue use of an opioid in order to function "normally").
  • When an opioid dependent individual ceases opioid use, they enter a dysphoric state of withdrawal. Withdrawal can also be precipitated if the individual takes an opioid antagonist drug.