Evidence for Tramadol and Codeine in Pain Control

Introduction to Tramadol and Codeine

Tramadol is classified as a WHO level 2 "weak" opioid with approximately one-tenth the potency of morphine, and is not recommended as first-line treatment for moderate to severe pain 1, 2
Codeine is also classified as a WHO level 2 "weak" opioid for moderate pain, with efficacy limited by genetic variability in metabolism and a ceiling effect 4, 6

Tramadol 250 mg daily in divided doses was generally comparable to acetaminophen/codeine combinations in long-term controlled trials, but effectiveness typically plateaus after 30-40 days in cancer patients 3, 1
Tramadol showed no superior analgesic efficacy compared to hydrocodone and codeine in 177 patients, but produced significantly more adverse effects 3
The American College of Physicians recommends careful attention to tramadol's numerous drug interactions and adverse effects, including seizure risk and serotonin syndrome 1

Codeine is a prodrug with little to no analgesic effect until metabolized to morphine via CYP2D6, and is ineffective in poor metabolizers 2
The European Society for Medical Oncology recommends codeine be used with caution, always combined with non-opioid analgesics, due to its unpredictable efficacy and potential for adverse effects 4, 6
Codeine's analgesic response is highly unpredictable due to genetic variability in metabolism, making it potentially toxic in ultrarapid metabolizers 2

Neither tramadol nor codeine demonstrates clear superiority over the other in head-to-head comparisons, and both have ceiling effects limiting dose escalation 3
The National Comprehensive Cancer Network recommends low doses of strong opioids combined with non-opioid analgesics as an alternative to weak opioids for moderate pain 3
Oral morphine remains the first-choice opioid for moderate to severe cancer pain, according to the European Society for Medical Oncology 3

For mild pain, start with non-opioid analgesics, and for moderate pain, consider low-dose strong opioids combined with non-opioid analgesics as the preferred option 6, 3
If using weak opioids, choose based on patient factors, such as avoiding tramadol in patients taking SSRIs or with a history of seizures, and avoiding codeine in known CYP2D6 poor or ultrarapid metabolizers 4, 1, 5, 2
Always combine weak opioids with non-opioid analgesics and prescribe prophylactic laxatives, and escalate directly to WHO step 3 strong opioids if inadequate response after 30-40 days or requiring >4 breakthrough doses daily 3, 1, 4