Opioid toxicity

Opioid toxicity can occur when there is accumulation of opioid in a patient which may be due to new doses in an opioid naive patient, changes in drug metabolism due to deteriorating renal or hepatic function, incompatibility with a specific opioid or rapid dose escalation. Patients in their final weeks of life may be thought to be deteriorating or entering their final days due to the effects of opioid toxicity and it is important to exclude this as a reversible cause of a change in condition. However overzealous treatment may lead to poorly controlled pain, so must be assessed and balanced carefully.

Signs

• Respiratory depression
• Myoclonus
• Hallucinations
• Delirium
• Excess sedation

Management

• Check renal and liver function and correct if able
• Withhold culprit medication, and remove opioid patches
• Ensure prn doses remain available at half previous dose
• Supportive care such as supplemental oxygen and IV fluids should be considered if dehydrated, reduced oral intake, and felt to be appropriate
• Avoid reversal with naloxone unless RR <8 and/or oxygen saturations are compromised, as this will also reverse analgesia and cause sudden, severe pain
• If reversal is required, use 50mcg IV naloxone (rather than 400mcg), repeated as necessary to reverse respiratory depression
• Consider opioid switch or restarting at half previous dose once symptoms improve

Naloxone use in therapeutic opioid toxicity

The aim is to reverse respiratory depression and maintain airway protective reflexes, not to fully reverse unconsciousness. Aim for a respiratory rate above 12 and a conscious level of alert or responding to voice on the AVPU scale.

Use of naloxone in reversal of therapeutic opioid medications

flowchart TD
    A["Initially, naloxone 50mcg-100mcg<br/>administered as an IV bolus"]
    B["If NO response seen after 1 minute:<br/><br/>Naloxone 50-100 mcg<br/>administered as an IV bolus"]
    C["If NO response after 1 minute:<br/><br/>Naloxone 50-100mcg<br/>administered as an IV bolus"]
    D["If still NO response after 1 minute:<br/>Repeat naloxone boluses up to a cumulative<br/>total of 2mg (Larger dose may be required<br/>in seriously poisoned)."]
    E["If still NO response,<br/>review diagnosis"]

    F["If a response is seen,<br/>repeat last IV bolus of<br/>naloxone every 1-2 minutes<br/>until good response"]

    G["Good response<br/>(RR > 12 bpm AND improved<br/>AVPU to at least = V)"]
    H["Monitor<br/>• 15 min observations<br/>• Beware of re-sedation"]
    I["Consider the need for an<br/>IV naloxone infusion<br/>(Section 4) if patient<br/>becomes re-sedated as<br/>bolus effects wear off"]

    A --> B
    A --> F
    B --> C
    B --> F
    C --> D
    C --> F
    D --> E
    D --> F

    F --> G
    G --> H
    H --> I

    style A fill:#fbe4d8,stroke:#333
    style B fill:#f8cecc,stroke:#333
    style C fill:#f8cecc,stroke:#333
    style D fill:#ff1a1a,stroke:#333,color:#fff
    style E fill:#dae8fc,stroke:#333
    style F fill:#97d077,stroke:#333
    style G fill:#009933,stroke:#333,color:#fff
    style H fill:#009933,stroke:#333,color:#fff
    style I fill:#009933,stroke:#333,color:#fff