- it has 2 separate mechanisms of action
(i) opioid (mu-1)
(ii) inhibitis noradrenaline & serotonin reuptake.
That is to say - that the combination of these 2 effects is much greater than either effect added together - ie. a multiplicative effect. The inhibition of noradrenaline and serotonin occurs particularly in the decending pathways for inhibition of pain - in the brain stem and spinal cord.
When it was first re-marketed in Australia about 5 years ago, it was done on the premise that it has a lower potential for 'abuse'. However, that is not what we are seeing clinically - and also on here if you do a search on tramadol ! Many people do get a buzz out of it - and the buzz is not just the opioid related buzz - but more the enhanced [READ: synergistic opioid] Noradrenaline and Serotonin effect.
So in summary:
(i) Is an
excellent step down analgesic following joint replacement that I use routinely in many of my patients after they have come of an opioid based PCA or epidural - with very high patient satisfaction scores; usually about day 3-4.
(ii) Addictive liability is not Zero, but is not as great as with true opioids. In older patients taking it for prolonged periods of time and ceasing it, it has not been shown to induce a withdrawal syndrome - and hence physical dependence has not been observed in a clinical setting.
(iii) The concern in using it in opioid dependent patients is that it may precipitate a withdrawal syndrome from true opioids - as the efficacy at the opioid receptor is so much less than morphine, it actually blocks the effect of morphine and hence acts as a partial agonist (ie. able to antagonise a full agonist to some degree).
I believe (iii) has been described in a few case reports and has a theoretical base - but I haven't observed this as yet.
As for U40915's comment regarding addictive potential in patients' who have previously been dependent on opioids - again - this has been reported, and now the drug company in order to cover themselves medico-legally prints this in the product information. As for how clinically significant this is - again ... I have not seen someone
clinically have such a response ... but I am the last to say "I will never see it" ... one day ?
As for your sister's comments about it being an NSAID (related to ibuprofen) ... I'm afraid it has no Non-steroidal anti-inflammatory activity what-so-ever.
Hope this helps answer your question.
Ref:
The clinical use of tramadol hydrochloride: Bamigbade, Langford. Pain Reviews 1998;5:155-182
[ 06 June 2002: Message edited by: gasbo ]
[ 08 June 2002: Message edited by: gasbo ]