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Doses are either expressed in terms of
a definite fre-
quency (e.g.
1 g 4 times daily) or in the total daily dose
format (e.g.
6 g daily in 3 divided doses); the total daily
dose should be divided into individual
doses (in the
second example,
the patient should receive 2 g 3 times
daily).
The doses of
some drugs may need to be adjusted if
their effects are altered by concomitant use with other
drugs,
or in patients with hepatic or renal
impairment
(see Minimising Drug Interactions,
and Prescribing for
Patients with Hepatic or Renal Impairment).
Doses for specific patient groups (e.g.
the elderly) may
be included if
they are different to the standard dose.
Doses for children can be identified by the terms
NEO-
NATE
,
INFANT
, and
CHILD
, and will vary according to their
age or body-weight.
Conversions for
imperial
to metric measures can be
found in the glossy pages at the back of the BNF.
Selecting a suitable preparation
Patients should be prescribed a preparation that com-
plements their daily routine, and that provides the right
dose of
drug for
the right
indication and route of
administration.
In the BNF,
preparations usually follow immediately
after the monograph for the drug which is their main
ingredient.
The preparation record (see fig.
1) provides
information on the type of formulation (e.g. tablet),
the
amount of active drug in a solid dosage form,
and the
concentration of
active drug in a liquid dosage form.
The legal
status is shown for prescription only medi-
cines and controlled drugs;
any exception to the legal
status is shown by a Note immediately after the pre-
paration record or a footnote.
If a proprietary prepara-
tion has a distinct colour,
coating,
scoring,
or flavour,
this is shown in the preparation record. If a proprietary
preparation includes excipients usually specified in the
BNF (see p.
2), these are shown in the
Excipients
state-
ment, and if it contains clinically significant quantities of
electrolytes, these are usually shown in the
Electrolytes
statement.
Branded oral
liquid preparations that
do not
contain
fructose,
glucose,
or
sucrose are described as ‘sugar-
free’
in the BNF.
Preparations containing hydrogenated
glucose syrup, mannitol, maltitol, sorbitol, or xylitol are
also marked ‘sugar-free’ since there is evidence that they
do not cause dental caries. Patients receiving medicines
containing
cariogenic
sugars
should be
advised of
appropriate dental hygiene measures to prevent caries.
Sugar-free preparations should be used whenever pos-
sible.
Where a drug has
several
preparations,
those of
a
similar type may be grouped together under a heading
(e.g.
‘Modified-release’
for
theophylline preparations,
p.
181).
Where there is good evidence to show that
the preparations for
a particular
drug are not
inter-
changeable,
this is stated in a Note either in the Dose
section of
the monograph or by the group of
prepara-
tions affected. When the dose of a drug varies according
to different
formulations of
that
drug,
the right
dose
should be prescribed for the preparation selected.
In the case of compound preparations,
the prescribing
information of
all
constituents
should be taken into
account for prescribing.
Writing prescriptions
Guidance is provided on writing prescriptions that will
help to reduce medication errors,
see p.
5. Prescription
requirements for controlled drugs are also specified on
p.
8.
Administering drugs
If a drug can be given parenterally or by more than one
route, the Dose section in the monograph or preparation
record provides
basic
information on the
route
of
administration.
Further
information on administration
may be found in the monograph or preparation record,
often as a Note or Counselling advice. If a class of drugs
(e.g.
topical
corticosteroids,
p.
708)
share the same
administration advice,
this
may be presented in the
prescribing notes.
Appendix 6 (p.
892)
provides practical
information on
the preparation of intravenous drug infusions, including
compatibility of
drugs with standard intravenous infu-
sion fluids,
method of
dilution or
reconstitution,
and
administration rates.
Advising patients
The prescriber
and the patient
should agree on the
health outcomes that
the patient
desires and on the
strategy for achieving them (see Taking Medicines to
Best
Effect,
p.
1).
Taking the time to explain to the
patient
(and carers)
the rationale and the potential
adverse effects of
treatment
may improve adherence.
For some medicines there is a special need for counsel-
ling (e.g.
appropriate posture during administration of
doxycycline);
this is shown in
Counselling
statements,
usually in the Cautions or Dose section of a monograph,
or within a preparation record if
it
is specific to that
preparation.
Patients should be advised if treatment is likely to affect
their ability to drive or operate machinery.
Cautionary and advisory labels that
pharmacists are
recommended to add when dispensing are included in
the preparation record (see fig. 1). Details of these labels
can be found in Appendix 9 (p.
957);
a list of products
and their labels is included in alphabetical
order of the
non-proprietary and proprietary drug names.
Monitoring drug treatment
Patients should be monitored to ensure they are achiev-
ing the expected benefits from drug treatment without
any unwanted side-effects. The prescribing notes or the
Cautions in the drug monograph specify any special
monitoring requirements.
Further information on mon-
itoring the plasma concentration of drugs with a narrow
therapeutic index can be found as a Note under
the
Dose section of the drug monograph.
Identifying and reporting adverse drug
reactions
Clinically
relevant
Side-effects
for
most
drugs
are
included in the monographs.
However,
if
a class
of
drugs (e.g.
tetracyclines,
p.
346)
share the same side-
effects,
these are presented in the prescribing notes
while those unique to a particular
drug in that
class
are included in its individual
drug monograph.
Occa-
BNF 61
xiii