An Overview of Opioids

June 26, 2014 – 10:11 pm

Rx Focus

Yvette C. Terrie ,BSPharm,RPh

As a health care community renews its focus on safe opioids prescribing practices,pharmacists have a pivotal role to play in managing this critical therapy for chronic pain.

Opioid analgesic agents have been used for centuries for their analgesic effects and are considered to be the most commonly used pharmacologic agents for the management and treatment of moderate to severe pain. Although these agents are considered safe when used properly and under physician supervision,it is important to understand the risks and benefits associated with prescribing the agents in this pharmacologic class.

Opioids include full agonists,partial agonists,and antagonists. Opioid analgesics exert their pharmacologic effects by binding to specific receptors both within and outside the central nervous system.1 These receptors include mu,delta,and kappa opioid receptors (Table 12, 3 ).The effect on mu receptors is considered the most important,with its activation directly linked to both analgesic and euphoric effects.2, 4, 5 These receptors occur throughout the central nervous system,but particularly in areas and tracts associated with pain perception. Receptors are also located in some sensory nerves,on mast cells,and in some cells of the gastrointestinal (GI) tract.2, 5

Opioids can be categorized as endogenous (endorphins,enkephalins,dynorphins),opium alkaloids (morphine,codeine),semisynthetic (oxycodone),or synthetic (methadone,fentanyl). The classes of opioids are phenanthrenes,phenylheptylamines,and phenylpiperidines.2, 5

Pharmacokinetics and Routes of Administration

Most opioid analgesics are well absorbed when administered via subcutaneous,intramuscular,and oral routes; however,due to first pass effect,oral doses of opioids may need to be much higher when compared with parenteral doses to achieve the same therapeutic effect.2 Opioids are converted in large part to polar metabolites,which are mostly glucoronides,and are then readily excreted by the kidneys.2 Alternative routes of administration may include patient controlled analgesia,nasal insufflation,oral mucosa via lozenges,and transdermal routes. Transdermal routes provide stable drug plasma levels and are thought to provide better pain control.2 Fetanyl is considered the most successful opioid for transdermal administration and is indicated for use in the management of constant pain often associated with malignancies.2, 6 Rectal suppositories of morphine and hydromorphone are sometimes used when oral and parenteral routes are not a feasible route of administration.2


Related posts:

  1. Classification of Analgesics Drugs
  2. Opioid Analgesics
  3. About Opioid Analgesics