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Senior Citizens Handle Narcotic Pain Killers Better
Than Younger Patients
Younger people want to rapidly increase their dose
May 20, 2005 - Narcotic medications can safely and
effectively ease severe, chronic pain in older people with little risk
that these patients will seek ever-increasing doses, UCSF medical
scientists have found. Younger patients, however, are likely to want to
rapidly increase their medication dose, posing serious potential health
consequences.
The study is the first to systematically compare
younger versus older patients' desires and needs to escalate the dose of
opioid pain medications they take -- a class of drugs including
morphine, methadone and oxycodone (sold as OxyContin, Percocet among
others). Based on the new findings, the researchers suggest that the
drugs may be under-prescribed for older patients, yet pose unique risks
for younger patients.
Opioids have long been used for unremitting pain
caused by nerve damage, arthritis and other diseases, but clinicians and
patients often worry that use of the drugs will lead to patient requests
for ever-increasing doses. Extended opioid use at high doses can alter
immune and hormonal function and, ironically, increase pain sensitivity.
The escalating drug need, stemming from "tolerance" to a given dose,
also can become very costly.
The new findings show that patients 60 or older
faced a much lower risk of opioid "dose escalation" than did younger
patients. Older patients also received long-term pain relief from the
opioids whereas younger patients showed no long-term benefit.
The discovery about opioid tolerance and age was
uncovered from a study of patient records, and confirmed in animal
studies. The findings are being published in two papers in the June
issue of Anesthesia and Analgesia.
"We have found that older patients, often
discouraged from using opioids for pain management, actually gain
significant long-term relief with minimal risk of excessive dose
escalation or toxicity," said Pamela Palmer, MD, PhD, professor of
anesthesia at UCSF and senior author of the two papers. Palmer is
director of the UCSF Pain Management Center.
In addition, long-term use of opioids at moderate
levels does not pose an increased risk for cardiac or kidney damage or
gastric ulcers, as some Cox-2 inhibitors do -- a risk of greater concern
for older patients than younger ones, Palmer said. Sedation and
constipation are the main opioid side effects, but these can be managed
by modifying the selection of the opioid, the dosage and proper bowel
medications.
Researchers examined the medical records of 206
patients who had been treated for two years for severe,
non-cancer-related pain, either from nerve damage (called neuropathic
pain) or from arthritis, fibromyalgia and related conditions that cause
what is known as nociceptive pain. Patients were divided into younger
(less than 50 years old) and older (over 60) age groups.
The records showed that both groups started with
similar doses of morphine-like drugs and both took about 14 to 15 months
to reach their peak dose. But the average peak dose of the younger group
was more than twice that of the older group. In many cases, peak doses
for younger patients were well over half a gram per day of morphine or
related opioid.
Younger patients with nociceptive pain escalated
the drug dosage at a "tremendous rate" for more than a year, the
researchers report. Yet they did not achieve any long-term pain relief
from these high doses according to standard self-assessment scores. In
contrast, the older patients, with less than half the dose escalation,
reported significant relief from pain, the scientists found.
The researchers speculate that the difference
between the older and younger patients may be the result of molecular
changes in neurons that occur with aging, and they cite this as a
particularly important area for future research. They also recognize the
importance of a prospective study rather than a retrospective one, and
they are planning a follow-up study.
In an animal study, the scientists sought to
confirm the age-related difference in tolerance to opioid drugs. They
note that no study had systematically evaluated how quickly rats develop
tolerance to opioid pain medication as a function of age. Rats aged
three weeks, three months, six months and a year were given twice-daily
injections of morphine proportional to their weight, and pain-relief was
assessed in a standard procedure of applying heat to the rat's tail and
measuring how quickly the animal flicked its tail away from the heat
source.
The researchers found that the youngest rats
experienced drug tolerance more than five times sooner than the oldest
rats. Six-month-old and three-month-old rats showed a 250 percent and a
150 percent increase in time to tolerance compared with the
three-week-old rats, they reported. The findings are consistent with the
human studies in which older patients continue to experience benefit
from a given opioid dosage while younger patients need to escalate the
dosage.
Why the older patients found long-lasting pain
relief at lower doses -- a finding confirmed in the animal studies -- is
not certain, Palmer says. But the results suggest to the UCSF scientists
that use of opioids for pain relief in both the young and the old should
be reconsidered.
For older patients, opioids appear to be a safe,
effective medication to treat long-lasting, serious pain without the
increased risks posed by Cox-2 inhibitors and other anti-inflammatory
drugs, Palmer concludes. On the other hand, younger people should be
cautious of using daily opioids to treat chronic pain.
"Younger people are more vulnerable to opioid
tolerance and ever-escalating doses, and they are at much lower risk
than older patients for heart attack and gastrointestinal bleeding
linked to anti-inflammatory drugs," she said. In sum, younger patients
may be better candidates for the newer non-steroidal anti-inflammatories
and poorer candidates for opioids, while older patients might benefit
more from opioids but are at greater risk for serious side effects from
anti-inflammatory drugs, Palmer says.
Lead author on the retrospective patient pain study
is Chante Buntin-Mushock, MD, research fellow in the UCSF neurology and
anesthesia departments. Co-authors are Lisa Phillip, MD, and Kumi
Moriyama, MD, both in the anesthesia department at UCSF.
The research is supported in part by the U.S.
Public Health Service. Lead author on the animal study is Yan Wang, MD,
postdoctoral fellow in anesthesia at UCSF. Co-authors are James
Mitchell, MD; Kumi Moriyama, MD; Ki-jun Kim, MD, PhD; Manhoar Sharma,
PhD; and Guo-xi Xie, MD, PhD, all in the UCSF anesthesia department.
The National Institutes of Health supported the
study.
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