Home' Australian Pharmacist : Australian Pharmacist June 2016 Contents Australian Pharmacist June 2016 I ©Pharmaceutical Society of Australia Ltd.
CONTINUING PROFESSIONAL DEVELOPMENT
By using the opioid comparison chart
from the 2016 Australian Medicines
Handbook, it can be determined that she
is taking approximately the equivalent
daily dose of 240 mg oral morphine.
When asked to rate her pain on a scale
of 0–10 (where 10 is the worst pain she
has ever experienced and 0 is no pain),
she stated that it was mostly about 7,
but was 9 in the mornings.
Such a high dose of opioid – for
little effect it would seem – begs the
questions of whether or not the use
of an opioid is valuable for Mrs PM
and whether this level of opioid use is
What is the evidence for opioids
in chronic non-cancer pain?
For acute pain and cancer pain, the use
of opioids is virtually undisputed but the
evidence for opioid use in chronic non-
cancer pain (CNCP) is poor.2,3 Chronic
pain is classified as constant daily pain
lasting for three months or more, in the
past six months.
Between 1992 and 2012, opioid
dispensing episodes increased 15-fold
(from 500,000 to 7.5 million).
analysis of the BEACH* data, it seems
fair to say that much of this is being
prescribed for CNCP.
This is of concern given the lack of
evidence for the use of opioids in CNCP.
Cochrane reviews on the studies that
have been conducted rate the quality of
the evidence as very low to moderate.
One such review, in 2013, on the efficacy
of opioid analgesia in chronic low back
pain found all studies had a duration
of less than 15 weeks and showed only
a 2-point reduction in the pain scale
(on a 10-point pain scale) compared
to placebo.6 There are no studies of
greater than 1-year duration that have
compared opioid therapy with other
treatments to determine long-term
outcomes related to pain, function, or
quality of life.
Other studies looking at neuropathic
pain show that opioids are only effective
for one in three patients and reduce pain
intensity by 30–50%.
have actually shown that use of opioids
for chronic pain may worsen pain and
Given this information, any initiation
of opioid for chronic pain should be
approached as a trial. If the use of
an adequate dose of opioid for four
weeks has not shown an improvement
in patient wellbeing and functioning,
then there is little evidence to support
continuation of the medication.
What are the long-term side
The side-effect profile from opioid
use in acute and cancer pain is well
defined and includes constipation,
nausea, sedation, dry mouth, respiratory
depression and pruritus.
is so common that Therapeutic
Guidelines recommends people be
informed to take a laxative concurrently
on initiation, e.g. Coloxyl with Senna.
However, long-term use of opioids in
CNCP is being increasingly associated
with more and more issues and the full
spectrum of possible adverse effects is
still being elucidated.
Some of these
possible adverse effects from opioids
can worsen the patient’s perception
of their pain and further complicate
Table 1. Adverse effects of long-term use of opioids2,4,7,15
• Fluid retention may exacerbate heart failure
• Observational studies showing increased myocardial infarction (MI)
• Lower limb cellulitis (due to immune compromise)
Gastrointestinal • Chronic constipation
• Nausea/vomiting (may occur due to constipation)
• Reduced production of saliva leading to dental caries
• Suppression of immune system (not well understood but opioids
can inhibit antibody production, lymphocyte activity and cytokine
Musculoskeletal • Diffuse muscle tenderness
• Myoclonus is seen with higher doses and in those with renal
Neuroendocrine • Long-term use suppresses the hypothalamic pituitary axis. This can lead
to low levels of all hormones.
• Osteoporosis – increased due to low oestrogen levels
• Impaired cognition
• Depression (low levels of testosterone lead to low mood)
• Impaired co-ordination (increase risk of fractures from osteoporosis)
• Impaired psychomotor function, e.g. when driving a car
• Respiratory depression
• Sleep apnoea (more marked with concomitant sedatives)
• Urinary retention
• Opioid-induced hyperalgesia (OIH)
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