Choice of opioid for acute pain management
Stephan A Schug
University of Western Australia, Perth, Australia
The
discussion on the choice of an opioid for acute pain management is an
ongoing one. The following presentation will attempt to illustrate that
there may not be one ideal opioids for the treatment of all acute pain
in all patients, but will offer some guidance for the selection of
opioids for certain patients in certain situations.
The most revealing study in this area rotated opioids administered by a
PCA device in a random order.[1] While overall there were few
differences in response or satisfaction, the individual experiences of
patients were very variable with some patients tolerating all three,
some showing a preference for one and some being intolerant of all.
Current understanding of opioids pharmacology does not explain these
differences, but the study supports the concept that there is not one
ideal opioid and that opioids rotation is a clinically useful concept.
This is well-established in cancer pain and chronic pain management,
where a switch of opioids is recommended in situations of inadequate
pain relief or intolerable opioids toxicity or adverse effects.[2]
Nevertheless, there are certain advantages and disadvantages of
various opioids in the acute setting. The most obvious recommendation
is, that the use of pethidine should be actively discouraged for the
treatment of all pain states.[3] Despite claims to the contrary, it
offers no advantages with regard to anticholinergic effects on the
biliary and renal tract; comparative studies failed to demonstrate any
advantages in treatment of colics. Furthermore, the neuroexcitatory
effects of its metabolite norpethidine limits titration in acute pain
and it shows a high propensity to induce drug seeking behaviour.
While morphine is the oldest and most widely used opioids in the
treatment of pain, its metabolites limit its use in many patients.
Morphine-6-glucuronide is a potent m-agonist and, if retained in
impaired renal function, can lead to sedation and respiratory
depression. Morphine-3-glucuronide is no opioids agonist, but can lead
to neuroexcitatory phenomena; concentrations of both metabolites are
increased with oral intake and in elderly patients.[4]
Hydromorphone, often hailed as a superior alternative to morphine,
offers no advantages with regard to efficacy or adverse effects and has
similar problems with regard to metabolites.[5]
These issues and own audit data have lead our service to use fentanyl
as the first line opioid for parenteral use to treat acute pain.
Fentanyl offers advantages with regard to fast onset of action and no
active metabolites.[6]
Oxycodone has become our oral opioids of choice, supported by good data
on efficacy in the acute setting.[7] Its metabolites contribute only
minimally to its effect and this offers advantages in at risk patients.
Methadone, while increasingly used in the setting of cancer and chronic
pain as an effective long-acting and cheap opioid, offers also
advantages due to its additional effects on NMDA receptors and
noradrenergic/serotonergic pathways. However, its long and
interindividually highly variable half-life makes it a less useful and
potentially dangerous opioid in the acute setting with a high risk of
accumulation.[8]
Our service does not encourage the use of weak opioids such as codeine
and dextropropoxyphene for the treatment of acute pain, as there are no
obvious advantages over the titration of strong opioids with regard to
effects and adverse effects.
Tramadol deserves special consideration here, although due to its
mechanism of action, it is often not regarded as an opioid, but more
appropriately as an 'atypical centrally acting analgesic'. It offers
advantages in situations, where the adverse effects of conventional
opioids are of concern. The risk of respiratory depression at
equianalgesic doses is lower than that of pure m-agonists and it causes
less constipation and enables faster bowel function recovery in the
postoperative period.[9]
Overall, this presentation illustrates, that there is not one opioids
for all acute pain in all patients, but that knowledge of
pharmacodynamics and -kinetics of the available opioids and
consideration of patient factors will enable the medical practitioner
to find a suitable compound for a given clinical situation. Last, not
least, preparedness to revise this choice in case of inefficacy or
adverse effects will benefit patients.
References:
[1] Woodhouse A, Ward M, Mather L. Inter-subject variability in
post-operative patient-controlled analgesia (PCA): is the patient
equally satisfied with morphine, pethidine and fentanyl? Pain.
1999;80(3):545-53.
[2] Quigley C. Opioid switching to improve pain relief and drug tolerability. Cochrane Database Syst Rev. 2004(3):CD004847.
[3] Latta KS, Ginsberg B, Barkin RL. Meperidine: a critical review. Am J Ther. 2002 Jan-Feb;9(1):53-68.
[4] Faura CC, Collins SL, Moore RA, McQuay HJ. Systematic review of
factors affecting the ratios of morphine and its major metabolites.
Pain. 1998 Jan;74(1):43-53.
[5] Quigley C. Hydromorphone for acute and chronic pain (Cochrane Review). Cochrane Database Syst Rev. 2002;1.
[6] Peng PW, Sandler AN. A review of the use of fentanyl analgesia in
the management of acute pain in adults. Anesthesiology. 1999
Feb;90(2):576-99.
[7] Edwards JE, Moore RA, McQuay HJ. Single dose oxycodone and
oxycodone plus paracetamol (acetominophen) for acute postoperative
pain. Cochrane Database Syst Rev. 2000(4):CD002763.
[8] Bruera E, Sweeney C. Methadone use in cancer patients with pain: a review. J Palliat Med. 2002 Feb;5(1):127-38.
[9] Scott LJ, Perry CM. Tramadol: a review of its use in perioperative pain. Drugs. 2000 Jul;60(1):139-76.
