Tramadol vs Other Analgesics

Tramadol hydrochloride

Tramadol hydrochloride is an orally active, centrally acting analgesic with a dual mechanism of action introduced in July 1994. It has been used in post-surgical pain, obstetric pain, and chronic pain of mechanical and neurogenic origin. Analgesic tolerance is not a significant problem, and psychological dependence and euphoric effects are minimal.

There are a significant number of patients in the chronic group who develop side-effects, but many of those who tolerate the drug get useful benefit in pain reduction. The most common adverse events (incidence of 1.6 to 6.1%) were nausea, dizziness, drowsiness, sweating, vomiting and dry mouth.

Unlike other opioids, tramadol has no clinically relevant effects on respiratory or cardiovascular parameters. Tramadol may prove particularly useful in patients with poor cardiopulmonary function, including the elderly, the obese and smokers, in patients with impaired hepatic or renal function, and in patients in whom nonsteroidal anti-inflammatory drugs are not recommended or need to be used with caution.

Several different studies on tramadol have shown the following:

Tramadol has a dose-dependent efficacy that lies between that of codeine and morphine, with a parenteral potency comparable to that of pethidine, i.e. about 10-20% of the gold standard morphine. Oral bioavailability is high (85-100%) and permits easy conversion from the oral to the parenteral route and visa versa.
Tramadol has been demonstrated to provide superior analgesia to combined acetaminophen-propoxyphene (i.e. Darvocet) in patients experiencing severe postoperative pain, and similar analgesia.
Four-week study of 390 elderly patients with chronic pain secondary to a variety of conditions, tramadol was found to provide comparable analgesia to acetaminophen with codeine without a significant difference in associated adverse effects.
A meta-analysis of RCTs in patients with acute pain found that single doses of tramadol 75mg to 150mg had analgesic efficacy similar to combinations of paracetamol 650mg plus propoxyphene 100mg and aspirin 650mg plus codeine 60mg. Short-term studies in chronic pain have shown tramadol 100mg three times a day to be as effective as dextropropoxyphene 100mg three times a day, and tramadol 50mg to be as effective as paracetamol 300mg plus codeine 30mg (both up to 8 capsules a day)

Mechanism of action

Tramadol shows a selective interaction with mu receptors, which are responsible for nociception, and has weak pharmacodynamic activity on other opioid receptors. At the same time, it acts synergistically on neuroamine transmission by inhibiting synaptic noradrenaline (norepinephrine) reuptake and inducing intrasynaptic serotonin (5-hydroxytryptamine; 5-HT) release.

Tramadol vs. Codeine

Relative to codeine, tramadol has similar analgesic properties but may have fewer constipating, euphoric, and respiratory depressant effects.

Metanalysis by Moore and McQuay indicates an appropriate dose response curve for tramadol, and suggests a reduced number needed to treat to show therapeutic efficacy as compared with codeine, in doses of 75 to 150 mg. Nausea, vomiting and dizziness are greater than with codeine, somnolence about the same and constipation much less. In the chronic pain situation nausea and vomiting are attenuated with usage, as is somnolence for both drugs, but constipation remains a particular problem with codeine and dihydrocodeine, and less of a problem with tramadol.

Tramadol vs. Morphine

Tramadol administration may produce a set of symptoms (including dizziness, somnolence, nausea, constipation, sweating and pruritus) similar to that of an opioid. However, tramadol causes significantly less respiratory depression than morphine. In contrast to morphine, tramadol has not been shown to cause histamine release. At therapeutic doses, tramadol has no effect on heart rate, left-ventricular function or cardiac index. Orthostatic changes in blood pressure have been observed.

Different studies have shown:

Tramadol may represent a superior choice over morphine for children undergoing adenotonsillectomy, with a potential to cause less postoperative sedation and respiratory depression.
Tramadol is as effective as morphine for moderate postoperative pain but it does appear to be less effective for severe acute pain.
Tramadol has been compared with morphine in patients with post-traumatic musculoskeletal pain in the pre-hospital setting. Intravenous tramadol 100mg was equivalent to 5-10mg morphine, with similar incidence of side effects and similar degree of patient satisfaction
Demiraran Y, Kocaman B, Akman RY. A comparison of the postoperative analgesic efficacy of single-dose epidural tramadol versus morphine in children. Br J Anaesth. 2005 Oct;95(4):510-3