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For established drugs there is no need to report well-
known, relatively minor side-effects, such as dry mouth
with
tricyclic
antidepressants
or
constipation
with
opioids.
Adverse reactions to medical devices
Suspected
adverse reactions to medical devices including dental or
surgical
materials,
intra-uterine devices,
and contact
lens fluids should be reported. Information on reporting
these can be found at:
www.mhra.gov.uk.
Side-effects in the BNF
The BNF includes clinically
relevant side-effects for most drugs; an exhaustive list is
not included for drugs that are used by specialists (e.g.
cytotoxic drugs and drugs used in anaesthesia).
Where
causality has not
been established,
side-effects in the
manufacturers’ literature may be omitted from the BNF.
Recognising that
hypersensitivity reactions can occur
with virtually all
medicines,
this effect is not generally
listed,
unless the drug carries an increased risk of such
reactions.
The BNF also omits effects that are likely to
have little clinical
consequence (e.g.
transient increase
in liver enzymes).
Side-effects are generally listed in order of
frequency
and arranged broadly by body systems.
Occasionally a
rare side-effect might be listed first if it is considered to
be particularly important because of its seriousness.
In the product literature the frequency of side-effects is
generally described as follows:
Very common
greater than 1 in 10
Common
1 in 100 to 1 in 10
Uncommon [‘less commonly’ in
BNF]
1 in 1000 to 1 in 100
Rare
1 in 10 000 to 1 in 1000
Very rare
less than 1 in 10 000
Special problems
Delayed drug effects
Some reactions (e.g.
cancers,
chloroquine retinopathy,
and retroperitoneal
fibrosis)
may become manifest months or years after exposure.
Any suspicion of such an association should be reported
directly to the MHRA through the Yellow Card Scheme.
The elderly
Particular vigilance is required to identify
adverse reactions in the elderly.
Congenital
abnormalities
When an infant
is born
with a congenital
abnormality or there is a malformed
aborted fetus doctors are asked to consider whether this
might be an adverse reaction to a drug and to report all
drugs
(including
self-medication)
taken
during
pregnancy.
Children
Particular vigilance is required to identify and
report
adverse reactions in children,
including those
resulting from the unlicensed use of
medicines;
all
suspected reactions should be reported directly to the
MHRA through the Yellow Card Scheme (see also
Adverse Drug Reactions in Children,
p.
15).
Prevention of adverse reactions
Adverse reactions may be prevented as follows:
.
never use any drug unless there is a good indica-
tion.
If
the patient
is pregnant
do not
use a drug
unless the need for it is imperative;
.
allergy and idiosyncrasy are important
causes of
adverse drug reactions.
Ask if the patient had pre-
vious reactions;
.
ask if
the patient
is
already taking other
drugs
including
self-medication
drugs,
health
supple-
ments,
complementary and alternative therapies
;
interactions may occur;
.
age and hepatic or
renal
disease may alter
the
metabolism or
excretion of
drugs,
so that
much
smaller
doses
may be
needed.
Genetic
factors
may also be responsible for
variations in metab-
olism,
notably of
isoniazid and the tricyclic anti-
depressants;
.
prescribe as few drugs as possible and give very
clear instructions to the elderly or any patient likely
to misunderstand complicated instructions;
.
whenever possible use a familiar drug;
with a new
drug,
be particularly alert for adverse reactions or
unexpected events;
.
warn the patient
if
serious adverse reactions are
liable to occur.
Oral side-effects of drugs
Drug-induced disorders of the mouth may be due to a
local
action on the mouth or
to a systemic effect
manifested by oral
changes.
In the latter case urgent
referral
to the patient’s medical
practitioner
may be
necessary.
Oral mucosa
Medicaments left in contact with or applied directly to
the oral mucosa can lead to inflammation or ulceration;
the possibility of allergy should also be borne in mind.
Aspirin tablets allowed to dissolve in the sulcus for the
treatment of
toothache can lead to a white patch fol-
lowed by ulceration.
Flavouring agents,
particularly essential oils,
may sen-
sitise the skin,
but
mucosal
swelling is
not
usually
prominent.
The oral mucosa is particularly vulnerable to ulceration
in patients treated with cytotoxic drugs,
e.g.
metho-
trexate.
Other drugs capable of causing oral ulceration
include captopril
(and other
ACE inhibitors),
gold,
nicorandil,
NSAIDs,
pancreatin,
penicillamine,
pro-
guanil,
and protease inhibitors.
Erythema multiforme or
Stevens-Johnson syndrome
may follow the use of a wide range of drugs including
antibacterials,
antiretrovirals,
sulfonamide deriva-
tives,
and anticonvulsants;
the oral
mucosa may be
extensively ulcerated,
with characteristic target lesions
on the skin.
Oral
lesions of
toxic epidermal
necrolysis
have been reported with a similar range of drugs.
Lichenoid eruptions
are associated with ACE inhi-
bitors,
NSAIDs,
methyldopa,
chloroquine,
oral
anti-
diabetics,
thiazide diuretics,
and gold.
Candidiasis
can complicate treatment
with antibac-
terials and immunosuppressants and is an occasional
side-effect of corticosteroid inhalers,
see also p.
185.
BNF 61
Adverse reactions to drugs
13
Adverse reactions to drugs