Tramadol is Weaker than Hydrocodone
Tramadol and hydrocodone have equivalent analgesic efficacy in head-to-head trials, but tramadol is approximately one-tenth as potent as morphine and produces significantly more side effects than hydrocodone, making it a less favorable option. 1
Direct Comparative Evidence
The most relevant evidence comes from randomized controlled trials directly comparing these medications:
In a head-to-head RCT of 177 cancer patients, tramadol versus hydrocodone showed no significant difference in analgesic efficacy, but tramadol produced a significantly higher percentage of side effects. 1
A separate RCT comparing hydrocodone/paracetamol (25 or 50/2500 mg/day) with tramadol (200 or 400 mg/day) in 118 patients found no significant difference in analgesia, but tramadol caused significantly more nausea, vomiting, vertigo, anorexia, and asthenia. 1
Potency Considerations
While the drugs may achieve similar pain relief at appropriate doses, their relative potencies differ:
Tramadol is approximately one-tenth as potent as morphine, with a maximum recommended daily dose of 400 mg for adults with normal hepatic and renal function. 1, 2
Hydrocodone is classified alongside tramadol as a "weak opioid" on WHO Step II of the analgesic ladder, but the comparative trials suggest hydrocodone achieves equivalent analgesia with better tolerability. 1
Adverse Effect Profile
The critical distinction lies in tolerability:
Tramadol consistently produces more adverse effects including vomiting, dizziness, and weakness compared to hydrocodone and codeine in double-blind studies. 1
Tramadol carries additional non-opioid risks including seizures (especially at doses exceeding 400 mg/day or in elderly patients ≥75 years), serotonin syndrome when combined with SSRIs or tricyclic antidepressants, and unpredictable efficacy due to CYP2D6 polymorphism. 1, 2, 3
Clinical Implications
For moderate pain requiring opioid therapy, hydrocodone is the preferable choice over tramadol due to equivalent efficacy with superior tolerability. 1
Key Caveats:
Both drugs are classified as "weak opioids" with ceiling effects and limited duration of effectiveness (30-40 days in cancer pain), after which patients typically require escalation to stronger opioids like morphine. 1
Tramadol should be avoided in patients taking serotonergic medications, those with seizure disorders, and elderly patients where lower doses are mandatory. 1, 2
The efficacy of tramadol varies significantly between individuals due to CYP2D6 genetic polymorphism, creating unpredictable responses ranging from overdosing to underdosing with standard doses. 3