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Chapter 58. Opioids, Induction Agents, Neuromuscular Blockers

Brian J. Egan, MD, MPH

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Opioids
MedicationPharmacologyClinical pearls
MorphineClassPhenanthrene
  • IV/IM dosing equipotent
  • IV dosing may produce less nausea/vomiting
  • Active metabolite (morphine 6-glucuronide) accumulates with renal insufficiency/failure
  • Intrathecal/epidural use: hydrophilic nature allows for single dose to have prolonged effect at the mu receptors within the substantia gelatinosa (12–24 h). Migration to brain stem can produce delayed respiratory depression
Dose1–3 mg
Relative potency1
Onset/peak5/20 min
MetabolismHepatic
Side effectsCauses common opioid side effects1 as well as histamine release
Hydromorphone (Dilaudid)ClassPhenanthrene
  • Good alternative to morphine in renal insufficiency
  • Purported to have less emetogenic effect compared with morphine
Dose0.1–0.4 mg
Relative potency7.5
Onset/peak5/20 min
MetabolismHepatic
Side effectsCommon opioid side effects1
Meperidine (Demerol)ClassPhenylpiperidine
  • Most effective opioid at decreasing postoperative shivering
  • Use in renal insufficiency can lead to accumulation of the metabolite, normeperidine, which can cause seizures
  • Atropine-like structure can increase HR; does not cause miosis
Dose12.5–100 mg
Relative potency0.1
Onset/peak5/20 min
MetabolismHepatic
Side effectsInteraction with MAOIs can cause fatal hypermetabolic reaction
Fentanyl (Sublimaze)ClassPhenylpiperidine
  • Use as analgesic component of TIVA at 0.2–1.5 μg/kg/h
  • Context-sensitive half-time (CSHT) leads to prolonged elimination with infusions greater than 2 h
  • Terminate infusion 30 min prior to expected emergence to allow drug accumulated in other compartments to be eliminated
Dose25–50 μg
Relative potency100
Onset/peak1/5 min
MetabolismHepatic
Side effectsCommon opioid side effects1 and chest wall rigidity
Sufentanil (Sufenta)ClassPhenylpiperidine
  • As component of TIVA has more favorable CSHT but will accumulate with longer infusions
  • Very rapid onset
Dose5–10 μg
Relative potency1,000
Onset/peak30 s/1 min
MetabolismHepatic
Side effectsCommon opioid side effects1
Alfentanil (Alfenta)ClassPhenylpiperidine
  • Good alternative to remifentanil as bolus agent for brief periods of more intense stimulation
  • Good choice of analgesic component of TIVA (0.5–3 μg/ (kg min)) when duration anticipated to be longer than 8 h (although remifentanil still superior in terms of recovery)
Dose100–300 μg
Relative potency15
Onset/peak30 s/1 min
MetabolismHepatic
Side effects
  • Common opioid side effects1
  • Chest wall rigidity at high doses or with rapid administration
Remifentanil (Ultiva)ClassPhenylpiperidine
  • With a flat CSHT with infusion of any duration, excellent TIVA component
  • Rapid onset and offset makes it good for blunting sympathetic effects of brief periods of increased stimulation
  • Very-low-dose infusions can be used for sedation; however, works synergistically with propofol to cause respiratory depression and apnea
Dose5–50 μg IV
Relative potency100
Onset/peak30 s/1 min
MetabolismTissue esterases
Side effects
  • Common opioid side effects.1
  • Acute opioid desensitization, hyperalgesia

1Common opioid side effects include nausea/vomiting, respiratory depression, urinary retention, pruritus, constipation, sedation, and miosis. Doses given are typical one-time bolus doses, not total doses for a given procedure.

Figure 58-1. Context-Sensitive Half-Time of Opioids
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