Opioid Allergy and Cross-Reactivity Considerations

Mechanism of Action and Classification

Hydrocodone and tramadol are both opioid analgesics with similar mechanisms of action, though tramadol has additional properties, according to the National Comprehensive Cancer Network 1, 2
Tramadol is classified as a weak mu-opioid receptor agonist with additional norepinephrine and serotonin reuptake inhibition properties, as stated by the National Comprehensive Cancer Network 3
Opioids are classified into three categories based on receptor action: pure agonist, partial agonist-antagonist, or mixed agonist-antagonist, as reported in the British Journal of Cancer 4

Despite its atypical properties, tramadol still acts on the same mu-opioid receptors as hydrocodone, creating risk for cross-reactivity in allergic patients, according to the National Comprehensive Cancer Network 1
Both hydrocodone and tramadol fall within the opioid class, with tramadol being considered a weak opioid (WHO level 2) and hydrocodone a stronger opioid, as classified in the British Journal of Cancer 4, 5

For patients with opioid allergies, non-opioid analgesics should be considered as first-line treatment, as recommended by the British Journal of Cancer and the Journal of Clinical Oncology 4, 6
NSAIDs may be appropriate alternatives for patients with inflammatory pain, particularly bone pain, though they have their own contraindications, as noted in the British Journal of Cancer 4
In cases where opioid therapy is necessary despite allergies, consultation with pain management and allergy specialists should be considered to determine the safest approach, as suggested by the Journal of Clinical Oncology 6

Documentation of opioid allergies should specify the exact nature of the reaction to help determine true allergies versus adverse effects, as recommended by the Journal of Clinical Oncology 6