A Textbook of Clinical Pharmacology and Therapeutics

• If possible, use oral medications. Once pain control is
established (e.g. with frequent doses of morphine orally),
change to a slow-release morphine preparation. This produces
a smoother control of pain, without peaks and troughs of
analgesia, which can still be supplemented with shorter
duration morphine formulations for breakthrough pain.
Tolerance is not a problem in this setting, the dose being
increased until pain relief is obtained.
Adverse effects of opioids should be anticipated.
Prochlorperazine or metoclopramide can be used to reduce
nausea and vomiting, and may increase analgesia. Stimulant
laxatives, such as senna, and/or glycerine suppositories should
be used routinely to reduce constipation. Spinal administration
of opioids is not routinely available, but is sometimes useful for
those few patients with opioid-responsive pain who experience
intolerable systemic side effects when morphine is given orally.
Bone pain is often most effectively relieved by local radiotherapy
rather than by drugs, but bisphosphonates (see Chapter 39)
and/or NSAIDs are useful.
Key points
Analgesics in terminal care
• Stepwise use of non-opioid to opioid analgesics as per
the WHO analgesic ladder (e.g. paracetomol)/weak
opioid (e.g. codeine)/strong opioid (e.g. morphine) is
rational when the patient presents with mild symptoms.
• In cases where severe pain is already established,
parenteral morphine is often needed initially, followed
by regular frequent doses of morphine by mouth with
additional (‘top-up’–’breakthrough’) doses prescribed
as needed, followed by conversion to an effective dose
of long-acting (slow-release) oral morphine,
individualized to the patient’s requirements.
• Chronic morphine necessitates adjunctive treatment with:
– anti-emetics: prochloperazine, metoclopramide;
– laxative: senna.
• Additional measures that are often useful include:
– radiotherapy (for painful metastases);
– a cyclo-oxygenase inhibitor (especially with bone
involvement);
– bisphosphonates are also effective in metastatic
bone pain
– an antidepressant.
MANAGEMENT OF POST-OPERATIVE PAIN
Post-operative pain provides a striking demonstration of the
importance of higher functions in the perception of pain. When
patients are provided with devices that enable them to control
their own analgesia (see below), they report superior pain relief
but use less analgesic medication than when this is administered
intermittently on demand. Unfortunately, post-operative
pain has traditionally been managed by analgesics prescribed
by the most inexperienced surgical staff and administered at the
discretion of nursing staff. Recently, anaesthetists have become
more involved in the management of post-operative pain and
Key points
MANAGEMENT OF POST-OPERATIVE PAIN 163
pain teams have led to notable improvements. There are several
general principles:
• Surgery results in pain as the anaesthetic wears off. This
causes fear, which makes the pain worse. This vicious
circle can be avoided by time spent on pre-operative
explanation, giving reassurance that pain is not a result of
things having gone wrong, will be transient and will be
controlled.
• Analgesics are always more effective in preventing the
development of pain than in treating it when it has
developed. Regular use of mild analgesics can be highly
effective. Non-steroidal anti-inflammatory drugs (e.g.
ketorolac, which can be given parenterally) can have
comparable efficacy to opioids when used in this way.
They are particularly useful after orthopaedic surgery.
• Parenteral administration is usually only necessary for a
short time post-operatively, after which analgesics can be
given orally. The best way to give parenteral opioid
analgesia is often by intravenous or subcutaneous
infusion under control of the patient (patient-controlled
analgesia (PCA)). Opioids are effective in visceral pain
and are especially valuable after abdominal surgery. Some
operations (e.g. cardiothoracic surgery) cause both
visceral and somatic pain, and regular prescription of both
an opioid and a non-opioid analgesic is appropriate. Once
drugs can be taken by mouth, slow-release morphine, or
buprenorphine prescribed on a regular basis, are
effective. Breakthrough pain can be treated by additional
oral or parenteral doses of morphine.
• Tramadol is useful when respiratory depression is a
particular concern.
• Anti-emetics (e.g. metoclopramide, prochlorperazine)
should be routinely prescribed to be administered on an
‘as-needed’ basis. They are only required by a minority of
patients, but should be available without delay when
needed.
• A nitrous oxide/oxygen mixture (50/50) can be selfadministered
and is useful during painful procedures,
such as dressing changes or physiotherapy, and for
childbirth. It should not be used for prolonged periods
(e.g. in intensive care units), as it can cause vitamin B 12
deficiency in this setting.
Analgesia and post-operative pain
• Pre-operative explanation minimizes analgesic
requirements.
• Prevention of post-operative pain is initiated during
anaesthesia (e.g. local anaesthetics, parenteral cyclooxygenase
inhibitor).
• Patient-controlled analgesia using morphine is safe and
effective.
• The switch to oral analgesia should be made as soon as
possible.
• Anti-emetics should be prescribed ‘as needed’, to avoid
delay if they are required.