Updated: 6/17/2021

Opiates & Analgesic Medications

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  • Introduction
    • Definitions
      • acute pain
        • implies presence of tissue damage
      • chronic pain (3-6 months)
        • no implication of tissue damage necessary
      • pathologic pain
        • pain from abnormal nervous system functioning (neuropathic)
    • Pathophysiology
      • afferent pain pathways
        • nociceptors
          • transduce signal through various substances
            • Substance P
              • a sensory neurotransmitter that plays an important role in pain
              • depletion of substance P increases the threshold to painful stimuli
              • Capsaicin is thought to function by decreasing Substance P
        • peripheral nerves
          • nociceptors transmit pain to type A and C peripheral nerve fibers
        • spinal cord
          • peripheral nerves transmit the pain signal via the dorsal column and spinothalamic tract
        • brainstem
          • spinal cord transmits the pain signal to the thalamus
          • site of pain modulation with endogenous opiates
    • Agents (details below)
      • Acetaminophen
      • NSAIDS
      • Opiates
      • Gaba synthesis agents
      • Adjunctive agents
  • Indications & Special Consideratoins
    • Pediatric patients
      • follow specific dosing guidelines for children which have been tested and recommended by the American Academy of Pediatrics
    • Geriatric patients
      • may have increased sensitivity to opioid pain medicines with higher rates of side effects
        • decreased total body mass with increased body fat percentage
        • potentially decreased hepatic and renal function
    • Obese patients
      • achieving adequate peri-operative pain control in the morbidly obese can be difficult
      • the most accurate method to control pain and avoid respiratory depression should include patient controlled analgesia (PCA), which is based on the patient's ideal weight
      • intramuscular injections should be avoided due to the difficulty of avoiding injection into muscle and the poor vascularity of the subcutaneous adipose tissue
    • Red-haired patients
      • often require more anaesthesia to maintain MAC levels and higher opioid dosages postoperatively compared to other hair types
    • Chronic regional pain syndrome
      • Vitamin C has been shown to possibly prevent CRPS specifically related to distal radius fractures
  • Acetaminophen
    • Mechanism
      • not fully understood
      • inhibits prostaglandin synthesis
      • minimal antinflammatory effects
    • As effective for pain control as aspirin
    • Toxicity
      • overdose leads to hepatic disfunction
      • contraindicated in the setting of pre-existing hepatic dysfunction
  • NSAIDs
    • Mechanism
      • decrease transduction of pain
    • See anti-inflammatory medications
  • Local anesthetics
    • Mechanism
      • decrease transduction of pain
      • interfere with nerve conduction to provide a reversible loss of sensation in a specific location
        • affects the depolarization phase of action potentials (cells fail to depolarize enough to fire after excitation leading to a blocked action potential)
    • Examples
      • amide family
        • lidocaine (Xylocaine)
        • bupivacaine (Marcaine)
      • esters of p-aminobenzoic acid
        • procaine (Novocain)
        • butethamine (Monocaine)
      • esters of meta-aminobenzoic acid
        • cyclomethycaine (Surfacaine)
        • metabutoxycaine (Primacaine)
      • esters of benzoic acid
        • cocaine
        • ethyl aminobenzoate (Benzocaine)
    • Adverse effects
      • FDA warning on the administration of continuous intra-articular infusion of local anesthetics for pain control
        • Some patients have been noted to have chondrolysis following infusion
  • Opiates
    • Overview
      • useful in chronic nociceptive pain
    • Mechanism
      • perispinal method affects modulation of pain
      • systemic opiates change the perception and modulation of pain
    • Administration
      • oral, IV, intraspinal
      • oral administration preferred (more convenient and less costly)
        • bony procedures require more analgesia than soft tissue procedures
      • patient compliance can improve with long-acting preparations that providue more uniform serum drug levels
      • implantable systems are available for intrathecal administration
    • Prescription dosing guide for upper extremity surgery
      • no narcotics
        • trigger finger release, nonop Dupuytren's release, small lumps/bumps
      • 10 narcotic tablets
        • mucous cyst, carpal tunnel, deQuervain’s, Dupuytren’s releases and small joint fusion
      • 20 narcotic tablets
        • wrist ganglion cysts, hand fracture ORIF, LRTI and tendon transfers
      • 40 narcotic tablets
        • large trauma, wrist fusion, open carpal surgery and DRUJ reconstruction
    • Chronic use
      • addiction occurs in a minority of patients
      • chronic opiates should be prescribed by pain management specialists
      • written contracts should be obtained
      • prescriptions should always be refilled in person
      • when used for OA, increases rate of surgical complications
  • Methadone
    • Synthetic diphenylheptaine-derivative opioid receptor agonist
    • High bioavailability (three times as much as morphine), effective, and inexpensive
    • Metabolism
      • cytochrome P450 system
    • Rapid distribution phase (2-3 hours) and prolonged elimination phase (15-60 hours)
    • Caution
      • can accumulate to high levels with repeated dosing
      • rates of elimination vary considerably
      • risk of respiratory depression, cardiac toxicity (torsades de pointes)
      • consult with a qualified pain specialist when prescribing for the first-time
  • GABA agents
    • Agents
      • Pregabalin (Lyrica)
      • Gabapentin (Neurontin)
    • Mechanism
      • decrease transduction of pain
        • reduce hyper-excitability of voltage dependent Ca2+ channels in activated neurons.
    • Gabapentin is an anticonvulsant also used to treat neuropathic pain
      • binds presynaptic calcium channels to inhibit release of neurotransmitters
    • Efficacy
      • evidence of effectiveness primarily for postherpetic neuralgia, diabetic nueropathy, and fibromyalgia
      • little evidence for other uses, though often prescribed for other forms of chronic neuropathic pain (such as complex regional pain syndrome, CRPS)
      • gabapentin has been shown to be as effective and less expensive than pregabalin
    • Discontinuation requires a tapering dose
  • Muscle relaxants
    • Overview
      • Useful to treat pain secondary to muscle spasms
    • Agents
      • Cyclobenzaprine (Flexeril)
        • mechnism of action not fully understood
        • centrally acting
        • potentiates norepinephrine and binds serotonin receptors
    • Use
      • may decrease pain during first two weeks after an injury
      • no proven benefit after first two weeks
      • may be effective for fibromyalgia
      • not effective to reduce spasticity secondary to neuromuscular disorders
    • Toxicity
      • overdose rare
      • may interact with other substances
        • MAOIs
        • alcohol
  • Adjuvant agents
    • Heterogeneous class of medications the provide additive analgesic effect to traditional NSAIDs and opioids
      • anticonvulsants
      • antidepressants
      • antihistamines
      • psychostimulants
      • anti-spasmodics
Flashcards (0)
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Questions (9)

(OBQ18.153) Which of the following medications work by inhibiting prostaglandin E2 production through interleukin-1 beta?

QID: 213049
















L 5 A

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(SBQ17SE.62) A hand surgeon plans on performing a carpal tunnel release on a healthy 45-year-old female. Which of the following is true regarding pain management for this case in the post-operative setting?

QID: 211787

A prescription protocol does not affect prescription patterns



Narcotic medication will offer superior pain relief as compared to anti-inflammatory medication



Anti-inflammatory medication leads to more side effects than narcotic medication



The duration of post operative pain is longer with anti-inflammatory medication than with narcotic medication



Over half of opioid pills prescribed by hand surgeons are not used



L 2 A

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(SBQ16HK.17) A 65-year old male with worsening right hip osteoarthritis has failed nonsurgical management and would like to proceed with total hip arthroplasty. He has consulted with a pain management specialist and is treating his pain with opioids. If he is able to successfully decrease the amount of opioids he takes preoperatively by 50%, what effect would that have on his postoperative functional outcome?

QID: 211295

No effect



Worse outcome



Improved outcome compared to if he had not weaned from opioids, but less improvement compared to if he were opioid naïve



Improved outcome compared to if he had not weaned from opioids, and similar improvement in function compared to if he were opioid naïve



Improved outcome compared to if he had not weaned from opioids, and better outcomes compared to if he were opioid naïve



L 4 B

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(OBQ13.150) Figures A and B show radiographs of a 24-year-old female with a soccer injury. A physical examination reveals an isolated, closed injury with no clinical features of neurovascular injury or compartment syndrome. She has been consented to be treated with intramedullary nail fixation. A pre-operative note by the anaesthesiology team makes reference to the patients fair skin and natural red-hair color. How will this information affect the post-operative management of this patient?

QID: 4785

Longer duration of anticoagulation due to increased risk of DVT



Avoiding anticoagulation medications due to increased risk of bleeding



Require higher dosages of post-operative analgesia



Longer period of non-weight bearing on surgical limb



Avoiding opioids due to higher risk of unrecognized allergies



L 3 C

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(OBQ11.226) A 35-year-old male presents with pain and limited range of motion 3 months after arthroscopic Bankart repair of his right shoulder. His postoperative course included a continuous intra-articular infusion pump for 3 days, use of a sling for 4 weeks, and initiation of passive range of motion below the level of the shoulder. At 4 weeks postoperatively he started active range of motion exercises, and started an isotonic strengthening program at the 9 week interval. Which of the following options is the MOST appropriate step in his management?

QID: 3649

Reassurance and appropriate followup



Focused physical therapy on aggressive ROM exercises and modalities



Intra-articular injection of corticosteroids to decrease post-operative inflammation



Shoulder radiograph series to assess for chondrolysis



Arthroscopic vs open Bankart revision surgery for failed repair



L 3 C

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(OBQ08.249) What is the most appropriate delivery route for pain medication to a morbidly obese post-operative patient to ensure a therapeutic plasma concentration?

QID: 635

Oral tablets



Oral liquid solution



Subcutaneous injections



Intravenous patient controlled analgesia based on actual body weight



Intravenous patient controlled analgesia based on ideal body weight



L 3 D

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Evidence (32)
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