Tramadol Formulation Options
Tramadol is available in both tablet and injection formulations, with tablets being the most commonly used form in clinical practice. 1, 2
Available Formulations
Oral Formulations
- Immediate-release tablets/capsules: 50 mg strength 1
- Modified-release tablets: 100-150-200 mg strengths 1
- Oral drops: 100 mg/ml concentration 2, 3
Parenteral Formulations
- Injectable solution: For intramuscular, intravenous, and subcutaneous administration 3
Pharmacokinetic Differences Between Formulations
Oral Formulations
- Bioavailability: Approximately 75% after oral administration 2
- Peak plasma concentration: Reached within 2 hours for immediate-release formulations 2, 4
- Duration of effect: Approximately 6 hours for immediate-release, 12 hours for modified-release 1, 4
Injectable Formulations
- Faster onset of action compared to oral formulations
- Higher bioavailability due to bypassing first-pass metabolism
- Used primarily in acute pain settings where rapid analgesia is required 5
Clinical Applications by Formulation Type
Oral Tramadol (Most Common)
- Recommended for moderate pain (WHO level II analgesic) 1
- Starting dose: 50-100 mg every 4-6 hours as needed 4
- Maximum daily dose: 400 mg 1, 4
- Classified as a weak opioid with 0.1-0.2 relative effectiveness compared to oral morphine 1
Injectable Tramadol
- Used in acute moderate to severe pain settings 5
- Particularly useful in postoperative pain management 3
- Equivalent in analgesic efficacy to pethidine (meperidine) when administered intravenously or intramuscularly 5
Mechanism of Action
Tramadol works through a dual mechanism:
- Weak μ-opioid receptor agonist activity 2, 4
- Inhibition of serotonin and norepinephrine reuptake 2, 4
The O-desmethyl metabolite (M1) has significantly higher affinity for opioid receptors than the parent compound, contributing substantially to the analgesic effect 2
Important Clinical Considerations
- Seizure risk: Tramadol can lower seizure threshold and should be avoided in patients with seizure disorders 6
- Serotonin syndrome: Risk increases when combined with other serotonergic medications 6, 2
- Metabolism variations: CYP2D6 polymorphism affects metabolism, with "poor metabolizers" having approximately 20% higher tramadol concentrations but 40% lower M1 (active metabolite) concentrations 2
- Drug interactions: Concomitant use with CYP2D6 inhibitors (fluoxetine, paroxetine, quinidine) can alter tramadol metabolism 2
Combination Products
Tramadol is also available in fixed-dose combination with paracetamol (acetaminophen) as 37.5/325 mg tablets, which can provide more effective analgesia than either agent alone for moderate to severe pain 7