6 The clinically important endpoint of therapy when naloxone is given is the reversal of respiratory depression, not the return of the patient to wakefulness. There is no need to administer naloxone in the absence of respiratory depression.
3-6 For these reasons, it is often given diagnostically when the possibility of opiate toxicity is in question e.g., a person found unconscious following an overdose of an unknown drug.7 Unfortunately, these are also the reasons that naloxone is often over-utilized. 3,4 In addition to being effective, naloxone has many features that make it an ideal antidote in the emergency setting: it is inexpensive (less than $ 1.00 for the average starting dose), it can be given via multiple routes, it has a very wide margin of safety, and it causes no side effects when given in large doses to people without exposure to opiates. This competitive inhibition is most pronounced at the mu receptor although opiate binding at the kappa and delta receptors is competitively blocked as well. 3,4 It works by competitively binding to the opiate receptor.
Naloxone is the antidote for opiate toxicity. The timing of this patient’s change in level of consciousness in relationship to his last dose of morphine, along with the physical findings of respiratory depression and hypotension, make opiate toxicity the likely cause of this patient’s worsening condition. 1,2 Clinically, miosis may be underreported as clinicians may not assess for this sign given the more pressing medical concerns these patients present with e.g., respiratory arrest. 1 In severe cases, hypotension is also present.
Opiate toxicity is classically defined as a triad of respiratory depression, central nervous system depression, and miosis. Because this patient has clinically significant respiratory depression, naloxone should be administered. Vital signs are rapidly assessed: HR 58 bpm, BP 62/40 mmHg, RR 4, oxygen saturation 55%. Within minutes of receiving the prescribed injection, he develops a marked decrease in level of consciousness. The patient is doing well until his first post-operative dose of morphine is given by the floor nurse. Upon arrival to the floor, his vital signs are: HR 78 bpm, BP 114/76 mmHg, RR 12, oxygen saturation 96%. The surgeon orders 10mg of morphine to be given intravenously every 3 hours as needed for post-operative pain in addition to re-institution of the patient’s oral morphine SR 60mg every 12 hours to begin that evening. Vital signs in the recovery room, just prior to moving the patient to the floor are: HR 76 bpm, BP 115/78 mmHg, RR 12 oxygen saturation 96%. Other chronic medications include pregabalin, enalapril, hydrochlorothiazide, clopidogrel, aspirin, and bisacodyl. For the previous 2 years, the patient has been taking morphine SR 60mg orally every 12 hours for pain. Ponte, PharmD, CDE, BCPS, FASHP, FCCP, FAPhA Case DescriptionĪ 76 year-old male with a history of cervical and lumbar spinal stenosis undergoes elective surgery to repair a broken hip he sustained in a fall.
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