The most common chief complaint resulting in an emergency department (ED) visit is pain. Pain can be subdivided into acute pain, which will be the focus of this chapter, or chronic pain. Acute pain is often shorter in duration (typically <30 days) and often occurs as a part of a single and treatable event. When assessing patients for acute pain conditions, one must consider not only patient comfort and self-determined pain scores, but also patient functionality. In addition, acute pain can often be recognized with a physiologic response such as tachycardia, hypertension, and/or diaphoresis that may help guide treatment.¹ Proper treatment of pain improves patient satisfaction and mood, decreases hospital length of stay, and decreases mortality.²

Acute pain conditions in the ED can be traumatic or nontraumatic including bone fractures, burns, procedural pain, visceral pain (ie, appendicitis, nephrolithiasis), or acute exacerbations of recurring pain conditions such as with sickle cell crisis and migraines. Analgesia in the ED should be patient-centered and pain syndrome targeted.¹ Treatment goals include not only providing relief for the acute pain but also decreasing complications including opioid dependence; physicians are encouraged to use a multimodal approach including both pharmacologic and nonpharmacologic treatments whenever possible.³

As discussed in Chapter 31, opioid analgesics, while seemingly effective in acute pain control, have many negative side effects. They are highly addictive and are associated with respiratory and CNS depression as well as risk of tolerance and development of hyperalgesia. Other side effects include euphoria, constipation, and pruritus and hypotension from degranulation of mast cells. Nonetheless, opioids may be appropriate for the treatment of traumatic injuries, vaso-occlusive crisis, and acute on chronic cancer-related pain.⁴

One of the most commonly used opioids is morphine, which is used as a baseline for which other opioids are measured.⁴ Parenteral morphine dosing ranges from 0.1 to 0.15 mg/kg with reassessment of pain every 5-15 minutes, onset within 5-10 minutes, and duration of action of 3-6 hours.² Oral morphine has 20%-25% bioavailability and is metabolized by the liver through glucuronidation to active metabolites, morphine-6-glucuronide and morphine-3-glucuronide, with M6G being more potent than morphine and M3G having the risk of neuroexcitatory effects. Morphine metabolites are renally excreted and may accumulate in elderly and renal failure patients.⁴

Fentanyl is metabolized by the liver, which utilizes CYP3A4 to produce inactive metabolites that are renally excreted; for this reason, fentanyl is safer to use in patients with renal failure.⁴ Initial IV dose is 1-1.5 µg/kg with time of onset in 1-2 minutes and typical duration of action about 30 minutes. It causes minimal histamine release, giving it a favorable hemodynamic profile, but caution should be taken at higher doses due to the risk of chest wall rigidity.²

Hydromorphone is a semisynthetic derivative of morphine that is seven times more potent than morphine.² It undergoes hepatic glucuronidation to its primary metabolite, hydromorphone-3-glucuronide, which has risks of neuro-excitatory effects, similar to M3G, and is renally excreted; hydromorphone should be used with caution in patients with renal failure.⁴ Initial IV dose is 0.25-0.5 mg with onset in 5-10 minutes, and duration of action of 3-6 hours.²

Until recently, treating acute pain in the ED with opioid analgesics had been considered a standard of care; however, from 1999 to 2018, almost 450 000 people died from an overdose involving opioids, including both prescription and illicit opioids.⁵,⁶ Because of the adverse effects of opioids and the worsening opioid epidemic, emergency physicians are now encouraged to avoid prescribing these medications for acute pain treatment when possible. It is important for the physician to recognize for whom opioids may be helpful as well as avoid prescribing opioids to patients at high risk of tolerance or abuse.

Some patients are considered higher risk for adverse events with opioid administration. These include older patients (65 years or older), those concomitantly taking other CNS depressant medications (ie, benzodiazepines, muscle relaxants, sleep aids), patients with a history of drug abuse or overdose, as well as patients with mental health conditions or sleep apnea.⁶

Current guidelines from the center for disease control (CDC) for pain treatment with opioid analgesics include the following:

In addition, ED physicians are encouraged to order urine drugs screen tests prior to prescribing opioids as well as review the prescription-monitoring program. The prescriptionmonitoring program allows emergency providers to identify patients with patterns of frequent opioid use/likely opioid abuse, ultimately helping the physician limit abuse potential as well as recognize patients with drug-seeking behavior who may benefit from treatment centers for addiction.⁶

Due to the risks with opioid analgesia and the rapidly growing epidemic, all physicians, especially those working in the ED, are encouraged to utilize nonopioid analgesics when appropriate prior to resorting to opioids to treat acute pain. For this reason, the rest of this chapter will focus on nonopioid analgesics.