General Principles
Once a decision has been made to use analgesic medications for cancer pain
management, the following general principles should be employed.
1. Analgesic Potency: Select the potency of the analgesic medication based
on the patient¹s self report of pain intensity {i.e., 0-10 scale} and the
impact of pain on functional status. With reports of mild to moderate pain
{6/10 } which minimally interferes with activities of daily living,
prescribe analgesics such as aspirin {ASA}, acetaminophen {APAP} or a
nonsteroidal antiinflammatory {NSAID}. Weak opioids such as codeine or
hydrocodone are appropriate therapies for pain of mild to moderate
intensity that moderately restricts activities of daily living. Several
combination medications are available such as APAP + hydrocodone and APAP
+ codeine}. If the patient reports severe pain, a strong opioid should be
given at the onset of pain treatment. With the exception of oxycodone none
of the strong opioid analgesics are combined with APAP or aspirin.
Caution should be exercised in increasing the number of tablets of
combination products given because toxic doses of the non-opioid are
rapidly reached.
Early reassessment of the effectiveness of the choice of opioid should be
done so that unrelieved pain is not unnecessarily prolonged. There should
be no reluctance to use strong opioids such as morphine, hydromorphone
(Dilaudid), levorphanol tartrate (Levo-Dromoran) or methadone.
Merperidine (Demerol) is not recommended for chronic pain treatment.
2. Route of Administration: Always administer analgesic medications orally
unless this route is unavailable or unreliable {e.g., vomiting, dysphagia,
intestinal obstruction, malabsorption syndromes}. Pain can be controlled
with oral medications. Equal efficancy can be achieved with oral
medications as with parentral medications provided equianalgesic doses
between oral and parenteral medications are used. (See Tables III, IV,
pages____) The benefits of oral medications as compared to parenteral
administration include convenience, lower costs, elimination of necessity
of IV-IM-SQ injections and enhanced patient participation in pain control.
For patients who cannot take medications orally, there are rectal,
transdermal, and intraspinal formulations of strong opioids available.
Again, simplicity should be the key word in selecting the appropriate
route.
3. Scheduled Medication Intervals versus P.R.N: Prescribe analgesics on a
scheduled, around the clock basis rather than on an "as needed" or "pro re
nata" (p.r.n.) basis. Studies have shown that patients require less
medication when it is prescribed on a scheduled basis rather than on a
p.r.n. basis. The physician should, therefore, instruct the patient to be
flexible in his or her taking of the medication and encourage taking the
amount required for pain relief regardless of time restrictions. IT SHOULD
BE REMEMBERED THAT PAIN IS A NATURAL ANTAGONIST TO THE ANALGESIC AND
RESPIRATORY DEPRESSANT EFFECTS OF OPIATES AND THAT OVERDOSE IS UNLIKELY AS
LONG AS A PATIENT HAS PAIN. If a patient requires medication more
frequently than prescribed, this usually indicates the prescribed dose is
inadequate to control the pain for the prescribed interval. Upward
adjustment in the dose should be made when this condition occurs. Emphasis
is on controlling the pain, i.e., preventing its recurrence.
4. Prevention and Treatment of Side Effects: Anticipate and aggressively
treat side effects before they occur. {See section on SIDE EFFECTS, PAGE--}
5. Evaluation of Response: Systematically review outcomes of analgesic
therapy. The frequency of evaluation depends upon patient characteristics
but general principles include reevaluation: 1) at regular intervals after
initiating therapies and after changes in therapies; 2) with each new
report of pain and 3) at 15-30 minutes after parenteral administration and
1 hour after oral administration during rapid titration of the dose or
with unstable pain. If the pain is not relieved by the dose prescribed,
increase the dose by 50-75%, and an increase of 100% may be necessary.
Continue to increase the dose until the pain is relieved, intolerable and
or untreatable side effects occur or it is determined that opioids alone
are ineffective. This maneuver is the pharmacological principle of
³dosing to effect². It is effective because there is no ³ceiling effect²
of the dose with opioids, especially in the treatment of nonceptive pain.
If pain is relieved by opioids but intolerable side effects develop {e.g.,
somnolence, impairment of thinking or ability to concentrate}, consider
changing to an equal potent opioid, changing the route or adding an
adjuvant medication. Opioids have differing opioid binding site
affinities; consequently, changing to an opioid with a different binding
profile may allow for a reduction in dose due to incomplete cross
tolerance. Changing routes {e.g., parenteral to intraspinal} will decrease
total dose requirements because of the differences in pharmokinetics. If
it is determined that opioids provide only partial relief, consider the
use of adjuvant therapies. The selection of adjuvant therapies depends on
the etiology of the pain. Tricyclic antidepressants and anticonvulsants
are often used in the treatment of neuropathic pain {SEE ADJUVANT
THERAPIES, Page --}. Psychological factors {e.g., depression, anxiety,
preexisting psychiatric diagnoses} may play a role in pain perception and
response. A psychological evaluation may be warranted.
6. Placebos: Do not use placebos to evaluate a patient's pain report.
Responses to placebos defy interpretation. It is not known why about one
third of patients with acute tissue damage (nociceptive) pain (e.g., from
fractures and other trauma) will respond to placebos. Responses may be due
to activation of the endogenous opiate system. Not only can nothing be
concluded from a response to a placebo, but use of placebos undermines the
doctor/patient relationship by adding an element of distrust. The
physician should be able to determine whether a patient is a drug seeker
or abuser by more positive, straightforward means.
