Tramadol vs Other Analgesics
Tramadol hydrochloride is an orally active, centrally acting analgesic with a dual mechanism of action. It has been used in post-surgical pain, obstetric pain, and chronic pain of mechanical and neurogenic origin.
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.
Tramadol has a dose-dependent analgesic 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.
Mechanism of action
Structurally tramadol is not an opiate, but it exhibits some opioid properties.
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.
Respiratory depression with tramadol is less pronounced, and occurs less often, in comparison to equianalgesic doses of morphine. In large clinical and post-marketing studies including over 21,000 patients, no clinically relevant respiratory depression was reported. However, respiratory depression can occur, in particular with overdose or with impaired renal function.
Another opioid side effect, which is reduced with tramadol use, is constipation. Clinically this has proven to be a significant advantage with long-term therapy, but could also be beneficial in the prevention of ileus postoperatively.
Sweating is a side effect specific to tramadol, due to its monoaminergic effects.
Tramadol appears to carry the same risk of urinary disorders (difficulty in micturition, urinary retention) as other opiates.
Tramadol is more potent than codeine 21. It has fewer constipating, euphoric, and respiratory depressant effects.
Chronic back pain
Codeine/paracetamol combination provides more effective pain improvement in moderate-to-severe low back pain and has better tolerability compared to tramadol/paracetamol 22.
Pain in dentistry
Tramadol maximum analgesic efficacy for relieving acute pain after oral surgery appears to be similar to that of 60 mg of codeine alone but less than that of a full therapeutic dose of codeine combination, such as aspirin/codeine or acetaminophen/codeine 20.
Tramadol has limited indication for management of acute pain in dentistry, possibly as an alternative analgesic when gastrointestinal side effects contraindicate the use of nonsteroidal anti-inflammatory drugs and when codeine/acetaminophen combination analgesics are not well-tolerated or are contraindicated.
Meperidine is a synthetic opioid agonist at mu and kappa opioid receptors. Structurally, meperidine is similar to atropine, and exhibits a mild atropine-like antispasmodic effect. Meperidine has poor oral bioavailability and a variable absorption after intramuscular injection.
Meperidine has rapid onset and relatively short duration of analgesia (about 2-3 hours).
Pethidine produces better analgesic efficacy than tramadol, especially in the second stage of labour. However, tramadol provides a shorter duration of labour and is better tolerated 6.
Analgesia for adenotonsillectomy
The results of comparative study suggest that pethidine given with induction of anaesthesia provides better analgesia during and after tonsillo-adenoidectomy than does tramadol. The delay to recovery of spontaneous respiration with pethidine suggests a greater safety profile of tramadol 2.
Another study has shown that meperidine appears to be more effective for pain relief and provides better emergence characteristics than tramadol after tonsillectomy in children 5.
In clinical trial meperidine and tramadol produced comparable analgesia in patients after orthopedic surgery4. Onset of analgesia for meperidine was 10 min and for tramadol more than 30 min.
Side effects and tolerability
Tramadol has superior safety profile. Pethidine is associated with a significantly higher frequency of adverse events and a significantly
lower respiratory rate in the neonates 6.
Morphine is the prototype pure mu-receptor agonist opioid, against to which all other opioid analgesics are compared.
Tramadol may produce a set of symptoms similar to opioids, including dizziness, somnolence, nausea, constipation, sweating and pruritus. However, tramadol causes significantly less respiratory depression than morphine. In contrast to morphine, tramadol has not been shown to induce histamine release. At therapeutic doses, tramadol has no effect on heart rate, left-ventricular function or cardiac index.
Different studies have shown:
Morphine provides greater (albeit not statistically significant) relief of radicular pain than tramadol 13.
Postoperative analgesia after tonsillectomy
Both analgesics are effective for postoperative pain relief in children after tonsillectomy. However, morphine may give better postoperative pain relief 15. Tramadol is better tolerated.
Postoperative analgesia after urological surgery
In the postoperative period, pain scores and the average time for analgesic requirement are similar for both. However, the incidences of allergic rash, itching, respiratory depression and sedation score are greater with the morphine 8.
Analgesia is similar with both tramadol and morphine for the management of pain in trauma 14.
Pain after abdominal surgery
Tramadol intramuscularly has postoperative analgesic activity similar to that of morphine. In multicenter trial comparing tramadol and morphine for pain after abdominal surgery after the first dose, pain intensity was reduced 36.2% with tramadol, and 51% with morphine 16.
Tramadol and morphine are potent analgesics in severe chronic pancreatitis pain when individually titrated. However, in clinical study tramadol interfered significantly less with gastrointestinal function and was more often rated as an excellent analgesic than morphine 12.
In clinical study there was no difference between the use of tramadol and morphine to treat pain after laparoscopic cholecystectomy from 90 min after the end of surgery. Morphine was more effective than tramadol as an intraoperative analgesic 17.
Tramadol has been demonstrated to provide superior analgesia to combined acetaminophen-propoxyphene in patients experiencing severe postoperative pain 7.
Unlike other opioids, tramadol is not usually associated with the development of tolerance, physical dependence or psychological addiction.
Although tramadol can produce drug dependence of the mu-opioid type (like codeine or dextropropoxyphene) and potentially may be abused, there has been little evidence of abuse in foreign clinical experience. In clinical trials, tramadol produced effects similar to an opioid, and at supratherapeutic doses was recognized as an opioid in subjective/behavioral studies. Tolerance development has been reported to be relatively mild and withdrawal when present, is not considered to be as severe as that produced by other opioids. Part of tramadol's activity and some extension of the duration of mu-opioid activity. Delayed mu-opioid activity is believed to reduce a drug's abuse liability.
References & Resources
Published: May 05, 2007