CHAPTER TWO Opioids Gregory B. Castelli and Winfred T. Frazier Opioids are a class of medications that have been widely used to relieve acute and chronic pain for millennia. Opioid is the modern term used to describe all substances that bind to opioid receptors, including agonists and antago- nists (Hemmings & Egan, 2013). Narcotics describe medications with the potential for abuse. Both terms are routinely used interchangeably in the clinical setting, with opioids as the overarching label for the entire class. Opi- ate is a less frequently used term that describes drugs directly derived from the opium poppy plant. As it is all encompassing, opioid is the most accurate nomenclature. For more on the history of opioids, see chapters 9 and 13. Opioids are divided into several different chemical and structural classes each opioid is available in various doses and delivery modalities (Ballantyne & Mao, 2003). Table 2.1 provides an overview of major opioid analgesic products. Commercially available products have different rates of onset and durations of action, which is important for clinicians to be aware of when prescribing these medications for patients (DiPiro et al., 2017). In addition to various dosage forms, rates of onset, and durations of action, prescription opioids come in several formulations, including immediate- and extended- release preparations, and various routes, including oral, transdermal, intra- venous, and intramuscular. Opioids have a high abuse and misuse potential, with some (e.g., heroin) commonly used illegally despite lacking clinical indications (Jamison & Mao, 2015). Opioid use and misuse is a major public health concern in the United States, with many federal agencies noting that the deleterious consequences of opioid misuse, including death, have reached epidemic proportions.
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