top of page


The Best in FOAM Education

  • Christopher Loh, MD

Approach to Pain Medication in the ED

General Tips

  • Pain is the most common presentation in the ED (75-80%)

  • Pain is a symptom, NOT a diagnosis

  • Pain is unique to the individual and is influenced by a multitude of factors to include culture, sex, age, severity of injury, co-morbidities, etc.

  • Titrate treatment to patient's functionality and pain perception

  • Vital signs cannot be used to accurately assess pain in the ED

  • Achieving analgesia with minimal side effects is important and a nuanced skill

  • Goal of treatment is not complete eradication of pain, but to reduce to acceptable levels for safe discharge or bridge to admission

  • Reassess pain frequently to determine analgesia efficacy

  • avoid relying on personal impressions on suspected pain ratings

Acetaminophen (Tylenol)

  • MOA: COX-3 inhibitor

  • Duration: 4-6hrs

  • Dosing

    • PO: 325mg, 500mg, 650mg, 975mg, 1,000mg every 6hrs

    • IV: 1000mg every 6hrs

    • PR: 650mg every 6hrs

  • Antipyretic and analgesic but NO peripheral anti-inflammatory properties

  • 2017 study found acetaminophen & Ibuprofen is as efficacious as opioid containing combinations for musculoskeletal pain

  • In mild-moderate pain, acetaminophen is the first line analgesic

  • safe in pregnancy and lactation (Category B 1st - 3rd trimester)

  • Maximal daily dose 4,000mg/d or 3,000mg/d in patients with liver disease or the elderly


  • MOA: nonselective COX-1, 2 inhibitors reducing prostaglandins

  • Common medication dosing

    • Ibuprofen

      • PO: 200mg, 400mg, 600mg every 6hrs

    • Ketorolac

      • IV: 15mg, 30mg every 6hrs

    • Naproxen

      • PO: 500mg every 12hrs OR 250mg every 6-8hrs

  • Evidence to suggest Ibuprofen maximal pain efficacy dose is 400mg. Higher doses do not improve pain efficacy, but increases risks for adverse effects


  • MOA: agonistic effects on Mu opioid receptors in central and peripheral nervous system

  • Morphine:

    • IV: 0.1mg/kg every 4-6hrs

    • PO: 10mg every 4-6hrs

    • Adverse effects: Hypotension, respiratory depression, sedation, histaminergic reaction, constipation

    • Metabolites excreted by the kidney, so will cause accumulation in renal failure patients

  • Fentanyl:

    • IV: 1mcg/kg every 1-2hrs.

    • Hemodynamically stable

    • Adverse effects: Sedation, Constipation, rigid chest syndrome

    • metabolized in liver, can cause accumulation in hepatic disease

  • Hydromorphone

    • IV: 0.015mg/kg every 4-6hrs

    • Adverse effects: Hypotension, respiratory depression, sedation, euphoria, constipation, histaminergic reaction

  • Oxycodone/Hydrocodone:

    • PO: 5-10mg every 4-6hrs

    • Adverse effects: Hypotension, respiratory depression, sedation, histaminergic reaction, constipation



IV/PO ratio

Equivalence dose ratio Morphine:X










IV 7:1; PO 4:1


0.1mg (100mcg)



IV 300:1





PO 3:1





PO 1:1

Sodium Channel Blockers

  • MOA: Inhibits sodium channels and inhibits glutamate release

  • Lidocaine

    • Injection 1%, 2%

    • topical 4%, 5%

    • maximal safe dose 4-5mg/kg (5-7mg/kg with epinephrine)

  • Bupivacaine

    • injection 0.25%, 0.5%, 0.75%

    • Maximal safe dose 2-3mg/kg

  • Ropivacaine

    • Injection 0.2%, 0.5%, 1%

    • Maximal safe dose 2-3mg/kg

  • Adverse effects

    • Allergic Reaction: typically in amide compounds (does not cross react to ester compounds)

    • Local Anesthetic Systemic Toxicity (LAST)

      • Cardiovascular effects: bradycardia, hypotension, AV block, decreased cardiac output, leading to cardiac and pulmonary arrest

      • Neurologic effects: numbness, lightheadedness, visual and auditory disturbances, convulsions, coma

Dopamine Receptor Antagonists

  • MOA: antagonism to D2, D3 receptors

  • sometimes used to treat acute headaches, gastroparesis, cyclic vomiting syndrome, cannabinoid-induced hyperemesis

  • Metoclopramide

    • IV/PO: 5mg, 10mg, 20mg q4-12hrs

    • Max dose 40mg/d

  • Prochlorperazine

    • IV/IM/PO: 10mg q6hrs

    • Max dose 40mg/d

  • Chlorpromazine

    • IV/PO: 10mg q6hrs

    • Max dose: 25mg/d

  • Haloperidol

    • IV/IM/PO: 5-10mg q4hrs

  • Droperidol

    • IV/IM 1.25-10mg q1-2hrs

  • Adverse effects: Cardiac arrhythmia (QT prolongation), Extrapyramidal Syndromes, Constipation, Hypotension, Dry mouth


  • MOA: alpha 2 adrenergic receptor agonist dampening CNS sympathetic pathways

  • Dose

    • Bolus: 0.5-1 mcg/kg

    • Infusion: 0.4-1.4 mcg/kg/hr

  • Adverse effects: Hypotension, Bradycardia


  • MOA: NMDA receptor antagonist

  • Pain/subdissociative dose

    • Bolus: 0.1-0.5mg/kg

    • Infusion: 0.1-0.2mg/kg/hr

  • Adverse effects: agitation, emergence reaction


  • MOA: sodium channel inhibitors

  • Gabapentin

    • PO: 100mg TID, titrated up to 1,200mg TID

    • Max dose: 3,600mg/d

  • Pregabalin

    • PO: 50-75mg, titrated up to 300mg

    • Max dose: 600mg/d

  • Adverse effects: fatigue, dizziness, ataxia, thrombocytopenia, angioedema, rhabdomyolysis

Clinical Pearls: Back Pain

  • Back pain leads to more disability than any other condition (depression, stress, exacerbation of underlying conditions)

  • Pain recurs in approximately 70% of patients treated in the ED

  • 1st line treatments: NSAIDs, trigger point injections, topical lidocaine, muscle-relaxants

  • 2nd line agents: Opioids

  • Resume activity as soon as possible

  • Recent systematic review and meta-analysis found NSAIDs resulted in a small but clinically significant improvement in back pain with an NNT = 6 (95% CI 4-10) to achieve clinically important pain reduction over placebo. NSAIDs were also shown to increase the risk of GI adverse events by 2.5x (95% CI 1.2-5.2)

  • Meta-analysis assessing acetaminophen for low back pain resulted in no difference in pain reduction between paracetamol (4g/d) and placebo at 1w, 2w, 4w, 12w for back pain reduction. Additionally, paracetamol did not affect quality of life, function, global impression of recovery, and sleep quality for all included periods.

  • 2017 ACP/APS joint recommendations indicate that acetaminophen, either as mono-therapy or combined with NSAIDs, is not effective for lower back pain.

  • Opioid combination analgesics (acetaminophen-oxycodone) were no more effective than NSAIDs alone for acute musculoskeletal pain relief, with the opioid combinations being associated with increased adverse effects

  • Research shows that those patients who received greater than a one-week prescription for opioids were twice as likely to have continued work-related disability at one-year follow-up.

  • Several SMRs have been shown to be superior to placebo in short-term pain reduction associated with acute, non-radicular back pain.

  • Due to lack of efficacy over NSAIDs alone as well as high risk of adverse effects, SMRs should be limited to patients who cannot tolerate NSAIDs or have not reported sufficient relief with NSAIDs.

  • If provider Discretion indicates that the benefit outweighs the risks, a short 2 to 3 day prescription with a full patient discussion regarding patient anticipated side effects should be considered

  • Benzodiazepines (diazepam) as an NSAID adjunct offers no improvement in functional outcomes or pain at one week and three months follow-up compared to NSAIDs alone

  • Use of benzodiazepines for acute back pain must further be weighed against the adverse effects.

Christopher Loh, MD


  • Henschke N, Maher CG, Refshauge KM, et al. Prognosis in patients with recent onset low back pain in Australian primary care: inception cohort study. BMJ. 2008;337:a171.

  • Friedman BW, Conway J, Campbell C, Bijur PE, John Gallagher E. Pain One Week After an Emergency Department Visit for Acute Low Back Pain Is Associated With Poor Three-month Outcomes. Acad Emerg Med. 2018;25:1138-1145.

  • Qaseem A, Wilt TJ, McLean RM, Forciea MA, Clinical Guidelines Committee of the American College of P. Noninvasive Treatments for Acute, Subacute, and Chronic Low Back Pain: A Clinical Practice Guideline From the American College of Physicians. Ann Intern Med. 2017;166:514-530.

  • Chou R, Qaseem A, Snow V, et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med. 2007;147:478-491.

  • Machado GC, Maher CG, Ferreira PH, Day RO, Pinheiro MB, Ferreira ML. Non-steroidal anti-inflammatory drugs for spinal pain: a systematic review and meta-analysis. Ann Rheum Dis. 2017;76:1269-1278.

  • Saragiotto BT, Machado GC, Ferreira ML, Pinheiro MB, Abdel Shaheed C, Maher CG. Paracetamol for low back pain. Cochrane Database Syst Rev. 2016:CD012230.

  • Deyo RA, Von Korff M, Duhrkoop D. Opioids for low back pain. BMJ. 2015;350:g6380.

  • Chou R, Huffman LH, American Pain S, American College of P. Medications for acute and chronic low back pain: a review of the evidence for an American Pain Society/American College of Physicians clinical practice guideline. Ann Intern Med. 2007;147:505-514.

  • Innes GD, Croskerry P, Worthington J, Beveridge R, Jones D. Ketorolac versus acetaminophen-codeine in the emergency department treatment of acute low back pain. J Emerg Med. 1998;16:549-556.

  • Lovell SJ, Taira T, Rodriguez E, Wackett A, Gulla J, Singer AJ. Comparison of valdecoxib and an oxycodone-acetaminophen combination for acute musculoskeletal pain in the emergency department: a randomized controlled trial. Acad Emerg Med. 2004;11:1278-1282.

  • Friedman BW, Dym AA, Davitt M, et al. Naproxen With Cyclobenzaprine, Oxycodone/Acetaminophen, or Placebo for Treating Acute Low Back Pain: A Randomized Clinical Trial. JAMA. 2015;314:1572-1580.

  • Webster BS, Verma SK, Gatchel RJ. Relationship between early opioid prescribing for acute occupational low back pain and disability duration, medical costs, subsequent surgery and late opioid use. Spine (Phila Pa 1976). 2007;32:2127-2132.

  • Franklin GM, Stover BD, Turner JA, Fulton-Kehoe D, Wickizer TM, Disability Risk Identification Study C. Early opioid prescription and subsequent disability among workers with back injuries: the Disability Risk Identification Study Cohort. Spine (Phila Pa 1976). 2008;33:199-204.

  • Witenko C, Moorman-Li R, Motycka C, et al. Considerations for the appropriate use of skeletal muscle relaxants for the management of acute low back pain. P T. 2014;39:427-435.

  • Cherkin DC, Wheeler KJ, Barlow W, Deyo RA. Medication use for low back pain in primary care. Spine (Phila Pa 1976). 1998;23:607-614.

  • Friedman BW, Cisewski D, Irizarry E, et al. A Randomized, Double-Blind, Placebo-Controlled Trial of Naproxen With or Without Orphenadrine or Methocarbamol for Acute Low Back Pain. Ann Emerg Med. 2018;71:348-56 e5.

  • Tisdale SA, Jr., Ervin DK. A controlled study of methocarbamol (Robaxin) in acute painful musculoskeletal conditions. Curr Ther Res Clin Exp. 1975;17:525-530.

  • Emrich OM, Milachowski KA, Strohmeier M. [Methocarbamol in acute low back pain. A randomized double-blind controlled study]. MMW Fortschr Med. 2015;157 Suppl 5:9-16.

  • van Tulder MW, Touray T, Furlan AD, Solway S, Bouter LM, Cochrane Back Review G. Muscle relaxants for nonspecific low back pain: a systematic review within the framework of the cochrane collaboration. Spine (Phila Pa 1976). 2003;28:1978-1992.

  • Reeves RR, Burke RS, Kose S. Carisoprodol: update on abuse potential and legal status. South Med J. 2012;105:619-623.

  • American Geriatrics Society Beers Criteria Update Expert P. American Geriatrics Society updated Beers Criteria for potentially inappropriate medication use in older adults. J Am Geriatr Soc. 2012;60:616-631.


bottom of page