Table 3.

Selected opioid safety considerations

OPIOIDSAFETY CONSIDERATION
Codeine
  • In breastfeeding women, there is risk of morphine toxicity in infants owing to rapid conversion of codeine to morphine

Tramadol
  • Associated with seizures in patients at high seizure risk, or when combined with medications that increase serotonin level (eg, SSRIs)

Morphine
  • In patients with renal dysfunction, morphine-6-glucuronide, an active metabolite of morphine, can accumulate to toxic levels

Oxycodone, hydromorphone, hydrocodone
  • As with all opioids, use with caution in patients at risk of opioid misuse and addiction

Fentanyl
  • Before starting fentanyl, ensure the patient has been fully opioid tolerant during the previous 2 wk (total dose of at least 60–90 mg/d morphine equivalence) on a scheduled dose (at least twice daily for CR or 4 times daily for IR)

  • Do not switch from codeine to fentanyl regardless of the codeine dose, as some patients taking codeine might have little or no opioid tolerance

  • Maintain the starting dose for at least 6 d and use extra caution with patients at higher risk of overdose (eg, the elderly, those taking benzodiazepines)

  • Advise the patient as follows:

    • -Be alert for signs of overdose; if detected, remove the patch and seek medical attention

    • -Apply the patches as prescribed; do not apply more than 1 patch at a time

    • -Avoid heat sources such as heating pads

    • -Enforce patch-for-patch exchange at pharmacy to reduce diversion

Methadone
  • Use methadone to treat pain only if you hold a written Health Canada exemption

  • Titration is hazardous because of its very long half-life, which leads to bioaccumulation

Meperidine
  • Not recommended for use in CNCP owing to poor bioavailability and inferior effectiveness to codeine

  • Normeperidine, a metabolite of meperidine, can accumulate with frequent use causing seizures and delirium

Acetaminophen-opioid combinations
  • Use with caution to not exceed maximum dose of 3.2 g/d of acetaminophen for adults (10 tablets/d of opioid-acetaminophen combinations)

  • No more than 8 tablets/d for tramadol-acetaminophen combinations

  • Warn alcohol drinkers to not mix alcohol with acetaminophen

CR formulations
  • Each CR tablet can contain a higher opioid dose than IR formulations do and can be converted to IR by biting or crushing the tablet

Tapentadol
  • Contraindicated in those with severe hepatic or renal dysfunction, or taking monoamine oxidase inhibitors

  • Small risk of seizure seen in postmarketing reports

Parenteral opioids
  • Parenteral opioids are not recommended for treatment of CNCP owing to increased risk of overdose, abuse, addiction, and infection

  • CNCP—chronic noncancer pain, CR—controlled release, IR—immediate release, SSRI—selective serotonin reuptake inhibitor.

    Adapted with permission from the Michael G. DeGroote National Pain Centre.46