This chapter discusses the special set of potential opioid-related
complications. Objective signs and symptoms of chronic pain are
hard to ascertain, whereas opioid use is associated with concrete
signs and symptoms that may act as markers for opioid side effects.
Most commonly, opioids produce constipation, nausea, vomiting, sedation,
and respiratory depression. Any adverse effects from opioids may
significantly limit therapy, and some can present with life-threatening consequences.
Unfortunately, there are few predictors of which patients will experience
which side effects and which particular opioids will produce them.
It is sensible to expect side effects and to take preventive action.
Since not all opioid-related toxicity can be predicted or prevented, patients
should be closely followed with a high level of suspicion. Effective
management includes anticipation of adverse effects when possible,
use of preventive measures, and choosing the best medication with
the optimum method of administration. Clear communication with the
patient, family, or nurse to ensure prompt recognition and response
to adverse effects is of utmost importance in order to recognize
and prevent possible adverse effects of opioid treatment.
Constipation is the most common dose-dependent side effect of
opioids. But unlike most other side effects, tolerance does not
develop. Thus, constipation can be expected throughout the duration
of opioid administration. Preventive therapy with cathartics and
adequate fluid intake is a mainstay of therapy and should be offered
at the time opioids are started and continued throughout opioid
treatment. Stool softeners and bulking agents such as bran or psyllium
derivatives alone will be inadequate because opioid-related constipation
results from decreased gut motility. Therefore, active stimulating
laxatives are effective and passive ones are not.
Severe constipation may respond to oral administration of naloxone,
which is an opioid antagonist with specificity to bowel. Administration
of oral naloxone has limited systemic bioavailability; however,
it has increased concentration and efficacy in the gastrointestinal
(GI) tract. Unfortunately, there is uncertainty about the dosing
regimen. Opioid withdrawal has been observed when oral naloxone
is administered at dosages exceeding 20% of the prevailing
24-hour morphine dose. It is suggested that initial individual oral
naloxone doses should not exceed 5 mg. In our institution, we start
with 1.6 mg to 2.4 mg taken orally (4 to 6 small ampules) every
4 hours until the first bowel movement, or for five doses. If ineffectual,
we may try another series with a higher dose. However, constipation
may be caused by factors other than opioids. Oral naloxone only works
when the constipation is solely opioid-related.
Since constipation can be mitigated by direct effects of antagonists
on the bowel, it is possible that opioids that are delivered without
direct bowel contact induce less constipation. There is evidence that
certain opioid products that are absorbed without contact to the
GI tract, such as transdermal fentanyl, induce less constipation
when compared with oral morphine at doses effecting the same degree
of pain relief. A significant reduction in the use of laxatives
has been reported. In ...