Codeine vs Tramadol
Clinical Comparison
Clinical Context
Both are WHO step 2 weak opioids. Codeine is simpler but has CYP2D6 variability issues. Tramadol's dual mechanism is useful for mixed nociceptive-neuropathic pain but carries serotonin syndrome and seizure risks. Neither should be used long-term without regular review.
Drug Profiles
Codeine
Weak opioid analgesic (WHO step 2)
Mechanism
Prodrug — demethylated by CYP2D6 to morphine (the active analgesic). Also has antitussive activity via central cough centre suppression
Indications
- Mild to moderate pain
- Cough suppression (linctus)
- Short-term diarrhoea management
Common Doses
30-60 mg every 4-6 hours (max 240 mg/day)
Route
Oral
Onset & Duration
Onset 30-60 min; duration 4-6 hours; half-life 3-4 hours
Tramadol
Weak opioid + monoamine reuptake inhibitor (atypical)
Mechanism
Dual mechanism: (1) weak mu-opioid agonist and (2) inhibits noradrenaline and serotonin reuptake, providing both opioid and non-opioid analgesia
Indications
- Moderate to moderately severe pain
- Neuropathic pain component (dual mechanism)
Common Doses
50-100 mg every 4-6 hours (max 400 mg/day); MR: 100-200 mg BD
Route
Oral, IV, IM
Onset & Duration
Onset 30-60 min oral; duration 4-6 hours (IR); half-life 5-6 hours
Key Differences
| Category | Codeine | Tramadol |
|---|---|---|
| Mechanism | Pure opioid prodrug (CYP2D6 to morphine) | Dual: weak opioid + serotonin/noradrenaline reuptake inhibition |
| CYP2D6 dependency | Critical — poor metabolisers get no effect, ultra-rapid risk toxicity | Less dependent — opioid component partly active without CYP2D6 |
| Serotonin syndrome risk | No serotonergic activity | Significant risk — avoid combining with SSRIs/MAOIs |
| Seizure risk | No effect on seizure threshold | Lowers seizure threshold — avoid in epilepsy |
| Constipation | Very common — often needs laxatives | Less constipation than codeine |
| Controlled drug schedule | Schedule 5 (low-dose OTC), Schedule 2 (higher doses) | Schedule 3 — stricter prescribing controls |
| Neuropathic pain | No specific neuropathic benefit | Dual mechanism provides some neuropathic pain benefit |
Mechanism
Pure opioid prodrug (CYP2D6 to morphine)
Dual: weak opioid + serotonin/noradrenaline reuptake inhibition
CYP2D6 dependency
Critical — poor metabolisers get no effect, ultra-rapid risk toxicity
Less dependent — opioid component partly active without CYP2D6
Serotonin syndrome risk
No serotonergic activity
Significant risk — avoid combining with SSRIs/MAOIs
Seizure risk
No effect on seizure threshold
Lowers seizure threshold — avoid in epilepsy
Constipation
Very common — often needs laxatives
Less constipation than codeine
Controlled drug schedule
Schedule 5 (low-dose OTC), Schedule 2 (higher doses)
Schedule 3 — stricter prescribing controls
Neuropathic pain
No specific neuropathic benefit
Dual mechanism provides some neuropathic pain benefit
Key Advantages
Codeine
- Well-established weak opioid
- Antitussive effect
- Can be combined with paracetamol (co-codamol)
- Cheap and widely available
- Useful for acute diarrhoea
Tramadol
- Dual mechanism — useful when neuropathic component present
- Less constipation than codeine
- Does not depend on CYP2D6 for primary activity
- Less respiratory depression than pure opioids
- IV/IM formulations available
Key Cautions
Codeine
- CYP2D6 ultra-rapid metabolisers — risk of morphine toxicity (especially in children — MHRA warning)
- CYP2D6 poor metabolisers — no analgesic effect (~6-10% Caucasians)
- Constipation (very common)
- Dependence and misuse potential
- MHRA: avoid in children under 12; contraindicated under 18 post-tonsillectomy
- Respiratory depression risk in ultra-rapid metabolisers
Tramadol
- Serotonin syndrome risk (with SSRIs, MAOIs, triptans)
- Lowers seizure threshold — avoid in epilepsy
- Schedule 3 controlled drug (codeine is Schedule 5 in lower doses)
- Nausea and dizziness common
- Dependence potential (possibly underestimated)
- Avoid with SSRIs/SNRIs without careful assessment
Clinical Verdict
Use codeine for simple nociceptive pain when paracetamol alone is insufficient (typically as co-codamol). Use tramadol when there is a neuropathic component or when codeine is ineffective, but check for SSRI co-prescription and seizure history first.
Medical Disclaimer: This comparison is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare professional before making prescribing decisions. Verify all drug information with current clinical guidelines (BNF, NICE, SmPCs).
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