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Continuous infusion devices
Although drugs can usually be administered
by mouth
to control
the symptoms of
advanced cancer,
the par-
enteral
route may sometimes be necessary.
Repeated
administration of
intramuscular injections
can be diffi-
cult
in a cachectic patient.
This has led to the use of
portable continuous infusion devices,
such as syringe
drivers,
to give a
continuous
subcutaneous
infusion
,
which can provide good control of symptoms with little
discomfort or inconvenience to the patient.
Syringe driver rate settings
Staff
using syringe drivers should be adequately
trained and different rate settings should be clearly
identified
and
differentiated;
incorrect
use
of
syringe drivers is a common cause of
medication
errors.
Indications for the parenteral route are:
.
the patient
is unable to take medicines by mouth
owing to
nausea and vomiting,
dysphagia,
severe
weakness,
or
coma;
.
there is
malignant bowel obstruction
in patients for
whom further surgery is inappropriate (avoiding the
need for an intravenous infusion or for insertion of a
nasogastric tube);
.
occasionally when the patient
does not wish
to take
regular medication by mouth.
Bowel
colic and excessive respiratory secretions
Hyoscine hydrobromide effectively reduces respiratory
secretions
and is
sedative
(but
occasionally causes
paradoxical
agitation);
it
is
given in a
subcutaneous
infusion dose
of 1.2–2.4 mg/24 hours.
Hyoscine butylbromide is used for bowel
colic and for
excessive respiratory secretions,
and is less sedative
than hyoscine hydrobromide.
Hyoscine butylbromide
is
given
in
a
subcutaneous
infusion
dose
of
60–
300 mg/24 hours
for
bowel
colic
and
20–120 mg/
24 hours for
excessive respiratory secretions (impor-
tant:
these doses of
hyoscine butylbromide
must
not
be confused with the much lower
dose of
hyoscine
hydrobromide
,
above).
Glycopyrronium 0.6–1.2 mg/24 hours by subcutaneous
infusion may also be used.
Convulsions
If a patient has previously been receiving
an antiepileptic drug
or
has a primary or
secondary
cerebral tumour
or
is at risk of convulsion (e.g. owing to
uraemia)
antiepileptic
medication
should
not
be
stopped. Midazolam is the benzodiazepine antiepileptic
of choice for
continuous subcutaneous infusion
, and it is
given initially in a dose of 20–40 mg/24 hours.
Nausea and vomiting
Haloperidol
is
given in a
subcutaneous infusion dose
of 2.5–10 mg/24 hours.
Levomepromazine is given in a
subcutaneous infusion
dose
of
5–25 mg/24 hours but
sedation can limit
the
dose.
Cyclizine is particularly likely to precipitate if
mixed
with diamorphine or
other
drugs (see under
Mixing
and Compatibility, below); it is given in a
subcutaneous
infusion dose
of 150 mg/24 hours.
Metoclopramide can cause skin reactions; it is given in a
subcutaneous infusion dose
of 30–100 mg/24 hours.
Octreotide (section 8.3.4.3), which stimulates water and
electrolyte absorption and inhibits water secretion in the
small bowel, can be used by subcutaneous infusion in a
dose of 250–500 micrograms/24 hours to reduce intes-
tinal
secretions and to reduce vomiting due to bowel
obstruction.
Doses of
750 micrograms/24 hours,
and
occasionally higher,
are sometimes required.
Pain control
Diamorphine is
the preferred opioid
since its
high solubility permits
a large dose to be
given in a small volume (see under Mixing and Compat-
ibility,
below).
The table on p.
24 shows approximate
equivalent doses of morphine and diamorphine.
Restlessness and confusion
Haloperidol
has little
sedative effect;
it
is given in a
subcutaneous infusion
dose
of 5–15 mg/24 hours.
Levomepromazine has a sedative effect;
it is given in a
subcutaneous infusion dose
of 12.5–200 mg/24 hours.
Midazolam is a sedative and an antiepileptic that may
be used in addition to an antipsychotic drug in a very
restless patient;
it is given in a
subcutaneous infusion
dose
of 20–100 mg/24 hours.
Mixing and compatibility
The general principle that
injections
should be given into separate sites
(and
should not
be mixed)
does not
apply to the use of
syringe drivers in palliative care.
Provided that there is
evidence of
compatibility,
selected injections can be
mixed in syringe drivers.
Not
all
types of
medication
can be used in a subcutaneous infusion.
In particular,
chlorpromazine,
prochlorperazine,
and diazepam are
contra-indicated as they cause skin reactions at
the
injection site;
to a lesser extent cyclizine and levome-
promazine also sometimes cause local irritation.
In theory injections dissolved in water for injections are
more likely to be associated with pain (possibly owing to
their hypotonicity). The use of physiological saline (sod-
ium chloride 0.9%) however increases the likelihood of
precipitation when more than one drug is used;
more-
over
subcutaneous
infusion rates
are so slow (0.1–
0.3 mL/hour) that pain is not usually a problem when
water is used as a diluent.
Diamorphine can be given by subcutaneous infusion in
a strength of
up to 250 mg/mL;
up to a strength of
40 mg/mL either
water for injections
or
physiological
saline
(sodium chloride 0.9%)
is a suitable diluent—
above that strength only
water for injections
is used (to
avoid precipitation).
The following can be mixed with
diamorphine
:
Cyclizine
1
Hyoscine hydrobromide
Dexamethasone
2
Levomepromazine
Haloperidol
3
Metoclopramide
4
Hyoscine butylbromide
Midazolam
1.
Cyclizine may precipitate at concentrations above 10 mg/
mL
or
in the presence of
sodium chloride 0.9%
or
as the
concentration of
diamorphine
relative
to cyclizine
in-
creases;
mixtures of
diamorphine and cyclizine are also
likely to precipitate after 24 hours.
2.
Special
care is
needed to avoid precipitation of
dexa-
methasone when preparing it.
3.
Mixtures
of
haloperidol
and diamorphine are likely to
precipitate after 24 hours if
haloperidol
concentration is
above 2 mg/mL.
4.
Under some conditions infusions containing metoclopra-
mide
become
discoloured;
such
solutions
should
be
discarded.
BNF 61
Prescribing in palliative care
23
Prescribing in palliative care