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opioid analgesics,
benzodiazepines,
antipsychotics,
and
antiparkinsonian drugs,
all of which must be used with
caution.
Similarly,
other organs may also be more sus-
ceptible to the effects of drugs such as antihypertensives
and NSAIDs.
Pharmacokinetics
Pharmacokinetic changes can markedly increase the
tissue concentration of a drug in the elderly,
especially
in debilitated patients.
The most
important
effect
of
age is
reduced renal
clearance.
Many
aged
patients
thus
excrete
drugs
slowly
,
and
are
highly
susceptible
to
nephrotoxic
drugs
.
Acute illness
can lead to rapid reduction in
renal
clearance,
especially if accompanied by dehydra-
tion. Hence, a patient stabilised on a drug with a narrow
margin between the therapeutic and the toxic dose (e.g.
digoxin)
can rapidly develop adverse effects
in the
aftermath of
a myocardial
infarction or a respiratory-
tract infection.
The hepatic metabolism of
lipid soluble
drugs is reduced in elderly patients because there is a
reduction in liver volume.
This is important
for drugs
with a narrow therapeutic window.
Adverse reactions
Adverse reactions often present in the elderly in a vague
and non-specific fashion.
Confusion
is often the pre-
senting symptom (caused by almost
any of
the com-
monly used drugs).
Other common manifestations are
constipation
(with
antimuscarinics
and many
tran-
quillisers) and postural
hypotension
and
falls
(with diur-
etics and many psychotropics).
Hypnotics
Many hypnotics with long half-lives have
serious hangover effects,
including drowsiness,
unstea-
dy gait,
slurred speech,
and confusion.
Hypnotics with
short half-lives should be used but they too can present
problems (section 4.1.1). Short courses of hypnotics are
occasionally useful
for
helping a patient
through an
acute illness or some other crisis but every effort must
be made to avoid dependence. Benzodiazepines impair
balance,
which can result in falls.
Diuretics
Diuretics are overprescribed in old age and
should not be used on a long-term basis to treat simple
gravitational
oedema which will
usually respond to
increased movement,
raising the
legs,
and support
stockings.
A few days of diuretic treatment may speed
the clearing of
the oedema but
it
should rarely need
continued drug therapy.
NSAIDs
Bleeding associated with aspirin and other
NSAIDs is more common in the elderly who are more
likely to have a fatal
or serious outcome.
NSAIDs are
also a special hazard in patients with cardiac disease or
renal impairment which may again place older patients
at particular risk.
Owing to the
increased susceptibility of
the elderly
to
the
side-effects of NSAIDs
the following recommenda-
tions are made:
.
for
osteoarthritis, soft-tissue lesions
, and
back pain
,
first
try measures
such as
weight
reduction (if
obese), warmth, exercise, and use of a walking stick;
.
for
osteoarthritis, soft-tissue lesions, back pain
, and
pain in rheumatoid arthritis
, paracetamol should be
used first
and can often provide adequate pain
relief;
.
alternatively,
a low-dose NSAID (e.g.
ibuprofen up
to 1.2 g daily) may be given;
.
for pain relief when either drug is inadequate, para-
cetamol in a full dose plus a low-dose NSAID may
be given;
.
if necessary, the NSAID dose can be increased or an
opioid analgesic given with paracetamol;
.
do not give two NSAIDs at the same time.
For
advice on prophylaxis of
NSAID-induced peptic
ulcers if
continued NSAID treatment is necessary,
see
section 1.3.
Other
drugs
Other
drugs which commonly cause
adverse reactions
are
antiparkinsonian drugs,
anti-
hypertensives,
psychotropics
,
and
digoxin
.
The usual
maintenance dose of
digoxin in very old patients is
125 micrograms daily (62.5 micrograms in those with
renal
disease);
lower
doses are often inadequate but
toxicity is common in those given 250 micrograms daily.
Drug-induced blood disorders are much more common
in the elderly. Therefore drugs with a tendency to cause
bone marrow depression (e.g.
co-trimoxazole,
mian-
serin
) should be avoided unless there is no acceptable
alternative.
The elderly generally require a lower maintenance dose
of
warfarin
than younger adults;
once again,
the out-
come of bleeding tends to be more serious.
Guidelines
Always consider whether a drug is indicated at all.
Limit range
It is a sensible policy to prescribe from a
limited range of drugs and to be thoroughly familiar with
their effects in the elderly.
Reduce dose
Dosage should generally be substan-
tially lower than for younger patients and it is common
to start with about 50% of the adult dose.
Some drugs
(e.g.
long-acting antidiabetic
drugs
such as
gliben-
clamide) should be avoided altogether.
Review regularly
Review repeat prescriptions regu-
larly.
In many patients it may be possible to stop some
drugs,
provided that
clinical
progress is monitored.
It
may be necessary to reduce the dose of some drugs as
renal function declines.
Simplify regimens
Elderly patients
benefit
from
simple treatment
regimens.
Only drugs with a clear
indication should be prescribed and whenever possible
given once or twice daily. In particular, regimens which
call for a confusing array of dosage intervals should be
avoided.
Explain clearly
Write full
instructions on every pre-
scription (
including
repeat
prescriptions)
so that
con-
tainers
can be properly labelled with full
directions.
Avoid imprecisions
like ‘as
directed’.
Child-resistant
containers may be unsuitable.
Repeats and disposal
Instruct patients what to do
when drugs run out, and also how to dispose of any that
are no longer
necessary.
Try to prescribe matching
quantities.
If these guidelines are followed most elderly people will
cope adequately with their own medicines. If not then it
is essential
to enrol
the help of a third party,
usually a
relative or a friend.
BNF 61
Prescribing for the elderly
25
Prescribing for the elderly