Opioid Blockers Help Relieve Problematic Pain
According to an evidence review from Pain Treatment Topics, opioid
antagonists like naloxone and naltrexone -- which block opioid drugs
from activating their receptors -- may be surprisingly helpful for
relieving difficult-to-treat pain conditions.
(c) Pain Treatment Topics, 2009
Opioid antagonists -- naloxone and naltrexone -- have demonstrated
unexpected qualities for enhancing pain relief.
Newswise — Achieving effective, durable, and safe pain relief,
especially in patients with chronic and/or severe pain conditions,
can
be difficult. For many types of pain, prescription opioids are among
the most effective analgesics. Yet, there is a growing body of
evidence suggesting potential benefits of opioid antagonists,
particularly naloxone and naltrexone. This is somewhat unexpected
because these drugs displace opioid molecules from their
neuroreceptors, and block opioids from attaching to and activating
those receptors.

In a peer-reviewed, evidence-based report for Pain Treatment Topics
(http://Pain-Topics.org) editor Stewart B. Leavitt, MA, PhD,
describes
naloxone and naltrexone pharmacology and the theoretical foundations
of opioid antagonists for pain management. Titled “Opioid
Antagonists,
Naloxone & Naltrexone -- Aids for Pain Management,” the 16-page
report
includes summaries of 17 studies -- case examples and clinical trials
– investigating opioid-antagonist therapy in adult humans. The
complete report with references can be freely accessed at the Pain-
Topics.org website at http://pain-topics.org/clinical_concepts/innovations.php

Naloxone and naltrexone have been extensively studied in the past,
and
are FDA-approved for the treatment of alcoholism or opioid addiction
(naltrexone) or opioid overdose (naloxone). A long-acting form of
naltrexone for intramuscular injection also is approved for addiction
therapy. These antagonists also are being used or tested as
ingredients in specially formulated opioid analgesics to deter their
misuse or abuse.

Leavitt notes, however, “doses of naloxone or naltrexone used in pain
management are generally much smaller than in other applications;
either in the 1 to 5 mg range, referred to as ‘low dose,’ or less
than
1 mg, in microgram amounts, designated as ‘ultralow dose.’ In animal
studies and human trials, low- or ultralow-doses of antagonists
appear
to enhance the pain-relieving efficacy of opioid-agonist analgesics,
such as morphine, oxycodone, and others. Along with this, tolerance
to
and physiologic dependency on opioid analgesics, as well as certain
opioid side effects, may be diminished. Furthermore, low-dose
naltrexone has been successfully tested by itself as monotherapy for
the management of several pain-related conditions, including Crohn’s
disease, irritable bowel syndrome, and fibromyalgia.”

Explanatory mechanisms of action behind the benefits of opioid
antagonists in pain management are still under investigation.
Essentially, appropriately low doses of opioid antagonists have been
postulated to “reset” the opioid-receptor system for a period of
time,
which seems analogous to how rebooting a malfunctioning computer
clears memory, refreshes the software, and often restores normal
function. With opioid-agonist therapy, the body becomes better
attuned
to the beneficial effects of both external opioids, such as morphine,
and naturally occurring internal opioids, such as endorphins.

Clinical research to date on low- or ultralow dose applications of
opioid antagonists for pain management in humans has been limited.
Still, the available evidence described in this report suggests a
number of possibilities that may be of interest to healthcare
providers and their patients with pain, including:

<> Brief detoxification using naloxone for difficult cases of opioid-
unresponsive intractable pain, opioid tolerance, or suspected opioid-
induced hyperalgesia.

<> Ultralow-dose naloxone combined with various opioid agonists for
managing postoperative pain.

<> Ultralow-dose naltrexone (oral) or naloxone (intrathecal) as a
component of intrathecal opioid analgesia for difficult cases of
intractable pain.

<> Ultralow-dose oral naltrexone combined with opioid agonists to
provide an opioid-sparing effect, offering equivalent pain relief at
lower opioid doses.

<> Oral ultra-low dose naloxone or naltrexone combined with oral
opioid analgesics to help prevent or reverse opioid-induced
constipation and to potentially reduce other opioid side effects.

<> Ultralow-dose naltrexone to help facilitate more comfortable
opioid-
agonist tapering.

<> Low-dose naltrexone monotherapy for Crohn’s disease, and possibly
for fibromyalgia and short-term treatment of irritable bowel
syndrome.

“Although further investigations to assess the safety and efficacy of
these applications would be appropriate,” Leavitt suggests, “both of
these agents have passed animal and clinical toxicity studies, and
have been used for years in applications other than those described
in
this research report. Therefore, it is not surprising that they have
exhibited favorable safety profiles when applied at low- and
ultralow-
dose levels, with few notices of adverse events or side effects at
these doses when used individually as monotherapy or in combination
with opioid analgesics.”

“Naloxone and naltrexone are available today as generic, economically
priced drugs, and it is important that practitioners become aware of
the therapeutic options that these may provide for patient care,”
Leavitt concludes. “However, it must be understood that opioid
antagonists are not yet FDA-approved for pain management purposes, so
low- or ultralow-dose naloxone or naltrexone would need to be
cautiously prescribed off-label for compounding at properly equipped
pharmacies.” ***

*** NOTE: The contents of this report are for educational purposes
and
are not intended to endorse or promote the off-label prescribing of
any drugs. Practitioners are advised to study the available evidence
and use professional discretion in their prescribing decisions.

Pain Treatment Topics and the associated Pain-Topics.org website
provide open and free access to noncommercial, evidence-based
clinical
news, information, research, and education on the causes and
effective
treatment of the many types of pain conditions. The project is
independently produced and currently supported by educational grants
from Purdue Pharma L.P., Stamford, Connecticut, and Covidien/
Mallinckrodt Inc., St. Louis, MO, leading manufacturers of opioid
analgesic products. The sponsors had no participatory role in the
initiation or development of this report on opioid antagonists in
pain
management.

Who loves ya.
Tom

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