Role of pharmacist in treatment of poisoning
Poisoning:-
Poisoning occurs
when any substance interferes with normal body functions after it is swallowed, inhaled, injected,
or absorbed. The branch of medicine that deals with the detection and treatment
of poisons is known as toxicology.
Unintentional poisonings:-
Community pharmacists can
promote poison prevention by encouraging all consumers to use child resistant
packaging and to keep all medications out of reach of children.
Specific
prevention information can be targeted to those picking up prescriptions for
opioids, cardiovascular medications, and sedative-hypnotic agents.
Grandparents
can be reminded to keep their medicines out of sight and reach and to remove
their medications from purses and luggage when visiting the grandchild’s home.
Parents
and caregivers must be reminded that child-resistant packaging is not
“childproof.”
While
legislation requires child-resistant packages to prevent at least 80% of
children younger than five years of age from opening them within a specified
time, 20% of young children are able to open child-resistant containers.
Parents,
grandparents, and caregivers should keep the phone number of the local poison
control centre with other emergency numbers, and know basic first aid in case a
poisoning occurs.
Community pharmacists can increase awareness by
distributing poison prevention pamphlets and poison control centre phone
numbers.
Intentional poisonings and overdoses:-
Anyone who expresses the hint of suicide should be taken seriously.
Poison prevention in this patient population will involve working with other
health care professionals, agencies, and family members.
The
community pharmacist can limit the number of pills provided at one time to a
suicidal or depressed patient and monitor the intervals between refills to
ensure appropriate use and prevent drug hoarding.
Pharmacists
must protect the patient’s right to confidentiality, but this may be breached
when failure to disclose information could place the patient in serious danger.
Before
confidentiality is compromised, the pharmacist should consult with other health
professionals involved with the patient. Intentional poisoning also occurs when
someone abuses medication for recreational purposes.
Patterns
of drug abuse differ by region, vary with time, and are often inventive.
Community
pharmacists must be knowledgeable about local drug abuse trends to address
adverse effects, potential interactions, drug diversion issues, and overdose
management.
Poison
control centres, drug information centres, local law enforcement agencies, and
internet sites can provide insight into local drug abuse patterns.
Awareness
of local drug abuse practices can also help pharmacists enhance patient care by
identifying patients at risk for drug overdose and misuse.
General
management of poisoning and
overdosage:
The mainstay
of management for poisoned patients is
providing symptomatic and supportive care.Antidotes for specific poisoning agents will also be used where appropriate. As for any seriously ill patient, a systematic and thorough
approach to treatment is required, including the following aspects
of care:
●
Initial “ABC”
(airway, breathing, circulation) assessment and resuscitation if necessary
●
A secondary survey for infection or trauma (of
the head and
cervical spine if a patient’s mental status
is abnormal) and metabolic derangements
●
Supportive care with continuous assessment and monitoring
●
Case-specific management such
as preventing further
absorption, using antidotes or
enhancing the elimination of the
toxic agent
Because of the serious
nature of some poisonings, early
treatment and supportive care may often proceed
rapidly without extensive investigations being carried out or an apparent
diagnosis being made.
Attention must be given to assessing a patient’s
vital signs and
to providing
immediate treatment of life- threatening
conditions such as hypotension, hypertension, bradycardia, tachycardia, car- diac arrhythmias, hyperthermia, hypothermia and respiratory depression.
Arrhythmias and conduction defects require cardiac monitoring and prompt treatment. Arterial blood gas measurements can be useful
to assess ventilation and oxy- genation and also to identify metabolic derangements
(eg, metabolic acidosis
caused by toxic alcohols
such as ethylene glycol or in salicylate poisoning). Where appropriate, blood samples should
be sent for
a full blood count, and to measure hepatic and renal function, electrolytes and blood glucose.After resuscitation and stabilisation, attention can turn to
identify the agents ingested using
data from the history and physical examination.Although it is unlikely that a single
abnormality detected on examination will help
differentiate poisoning from other causes of illness, or indicate a specific toxin,
a cluster of symptoms and signs in the same patient,
known as a toxidrome, may be of considerable value
in helping to identify a toxic agent.For
example, an opioid toxidrome is
characterised by impaired con- sciousness
and, although a number of agents are associated with depressed consciousness, when this symptom is coupled with pin- point pupils,
hypotension and respiratory depression, opioid
poisoning is the most likely cause.
The anticholinergic toxidrome (found with poisoning from drugs such as tricyclic
antidepressants and antihistamines) includes
tachycardia, dilated pupils, dry, warm skin, dry mucous membranes and urinary retention. Conversely, the cholinergic toxidrome, found after exposure to organophosphate and
carbamate insecticides or nerve agents, includes salivation, lacrimation, urinary and faecal incontinence, emesis, abdominal pain, diaphoresis and small pupils.
Gut decontamination
There is no evidence that inducing
vomiting with syrup
of
ipecachuana(or “ipecac”) or performing a gastric lavage (ie, stomach washout),has any impact on the outcome
of a poisoning.
Activated charcoal
(AC) acts by adsorbing ingested
substances and preventing their absorption from
the gut into the systemic circulation. It
is generally most effective if
administered within one, or perhaps two, hours of ingestion. For overdoses of drugs that enter the enterohepatic circulation, such as
carbamazepine, phenobarbitone, theophylline,
quinine or dapsone, multiple doses of activated charcoal (MDAC)
may be used, provided a patient’s bowel sounds are present.MDAC has also been used for overdoses of sustained
release preparations.
Disadvantage The main risk
with AC is aspiration if a patient has an unprotected airway. If this occurs, administration of AC via a nasogastric tube, after the patient has been intubated, is indicated.
There are a variety of AC preparations available, including
a sweetened version,
but unfortunately none is able to prevent AC being a particularly unpleasant substance to drink.This makes its use, especially in paediatrics, difficult.
Dose The usual
dose of AC is 50g in adults and 1g/kg body weight
for children under
12 years. When
using MDAC, these doses are repeated four hourly, although smaller doses may be given more frequently if necessary.
Contraindication It
is best to avoid mixing AC with food, such
as ice cream, to try to improve its palatability as this can reduce its adsorbent capacity.
Incompatibilities AC has a good adsorpive capacity for
most drugs and
chemicals, except for metals (eg, iron and lithium), alcohols (eg, ethanol,
methanol and ethylene glycol),
acids or alkalis.
Whole bowel irrigation (WBI) may be indicated where
there has been ingestion of high doses of medicines such as iron or lithium
tablets (which are not bound
by AC), sustained release preparations or when treating
“bodypackers” (i.e, those who
swallow illicit drugs for
smuggling purposes). WBI involves the oral administration of polyethylene glycol until
the rectal effluent is clear. In the UK, the only suitable product
is Klean-Prep.
Dose The adult dose is 1.5-2L/hr, usually
continued for two to six
hours. In children aged six to 12 years old the dose is 1L/hr and in those nine months to
six years old 500ml/hr. Klean-Prep can be made more palatable
by chilling it. Administration via a nasogastric tube may be necessary.
Enhanced elimination of toxins
Severely poisoned patients
are likely to require methods
to increase the elimination of the toxin from the body.
These will generally take place in an intensive
care unit.
Urinary
alkalinisation with sodium bicarbonate can
increase the elimination of weak acids because it prevents the ionised drug being reabsorbed in the renal tubules. It is most commonly
used in patients
with moderate to severe aspirin poisoning.
Dose In
adults, the dose of sodium
bicarbonate used is usually 1L of isotonic fluid (i.e, 1.26
per cent or 1.4 per cent) given intravenously over four hours.
Alternatively, 50ml boluses
of hypertonic (8.4 per cent)
sodium bicarbonate can be given, but this should
ideally be administered via a central
line, given the irritant nature of this preparation. In practice, a combination of the two regimens is often necessary to achieve adequate
urinary alkainisation. The bicarbonate dose, regimen and dose-timing should be titrated to achieve a urine pH of 7.5–8.5.The
urine pH should be checked at least hourly and patients should also have their
blood gases monitored regularly to ensure that systemic alkalinisation is not
occurring.
It is also important to monitor the serum potassium
concentration closely and titrate potassium replacement accordingly —
hypokalaemia will make it difficult to achieve alkalinisation. Once
alkalinisation is achieved, the serum potassium is likely to fall in response
to an increase in urinary potassium excretion.
Extracorporeal procedures such as
haemodialysis and haemoperfusion are only used in patients who have been
severely poisoned with a limited subset of drugs and chemicals — treatment of
such patients should always be discussed with a poisons unit. Haemodialysis may
be required in patients with severe aspirin, lithium, ethylene glycol or
methanol poisoning. There are limited data on the use of haemofiltration as a
method for toxin removal in the poisoned patient, but it may be required in
patients with renal failure or a severe metabolic acidosis. Charcoal
haemoperfusion may be used in patients with severe theophylline or
carbamazepine poisoning, although drug clearance is similar to that with MDAC
and so haemoperfusion is generally reserved for patients with life-threatening
toxicity.
Antidotes
Some general aspects of antidote use include the importance of
documenting a patient’s weight to ensure that a correct dose is used for
dose-adjusted treatments such as N-acetylcysteine for paracetamol poisoning.
Studies have shown that clinicians are poor at estimating patient’s body
weight.
In addition, prescriptions for antidotes should be written using
generic names, which helps avoid errors such as Parvolex (acetylcysteine) being
read as Pabrinex (thiamine).
Role of pharmacists
The most important
treatment measure for poisoning is prevention.Once a poisoning occurs it is
important to be able to provide highly skilled supportive medical care.It is
insufficient to focus only on simple first-aid measures, antidotal therapy or
home remedies.
For treatment of
poisoning pharmacist can do help to prevent poisoning and to improve treatment
thereof.
Pharmacists direct
and staff many regional poisoning centers.
They actually
provide consultation to physicians treating poisoned patients to assure quality
care.
1.
Undoubtedly,the most important role played by a pharmacist is
in the area of prevention.This role,relative to poisoning prevention packaging
of prescription drugs,was mentioned previously.However the role of pharmacist
is particularly critical with regard to OTC products.
With prescription
of medicines there is involvement of physicians who may provide prescription
and precautionary advice.
2. However,with OTC products the pharmacist is
only the person who is in position to perform these functions.
The pharmacist can
and should provide,explain and amplify directions for proper use of potentially
toxic materials,bearing in mind that concern is for the safety of patient and
for other household individuals.
Thus,dispensing of
toxic medication provides an opportunity to warn the buyer about the hazards of
leaving the material within reach un-suspecting children.
3. In some instances it is warning labels on the
products that pharmacist dispenses or to hand out patient information
materials.The dispensing of drug also provides opportunity to inquire and give
advice about facilities for safe storage.
Because of this
contact the pharmacist can play personalized role in cautioning about
prescription and commercial products.
4. The pharmacist can do much to reduce
aforementioned limitations of labeling.Although the public often may not read
or appreciate precautions on labels,the effectiveness of latter are increased
significantly if pharmacist takes time to explain them.
5. The pharmacist also has a unique role to play
in detecting product or labeling defects and an obligation to call to the
attention of appropriate manufacturers or regulatory agencies potential
labeling or product defects.
6. Finally pharmacist can assist greatly in the
educational efforts of community by distributing literature and by providing
space for displays related to poisoning prevention.
Poison prevention education can be incorporated
into many facets of community pharmacy practice. The approach to preventing an
unintentional poisoning will likely vary from that of an intentional poisoning.
However in both situations, prevention begins with the identification of
high-risk patients.
7. Pharmacists have a key
role in ensuring the timely availability of any antidote that might be
indicated and giving advice on treatment regimens and possible complications.
Guidelines have recently been produced by the British Association of Emergency
Medicine (BAEM) and the Guy’s and St Thomas’ Poisons Unit, which group the
availability of antidotes by the urgency of clinical need. The antidotes held
at each health care facility should be assessed to ensure that stock levels are
appropriate when taking into account the epidemiology of poisoning in their
local area. Regular expiry date checks should be carried out. The “Rarely used
medicines” database run by London, Eastern and South East Specialist Pharmacy
Services is a resource supporting pharmacy staff to obtain medicines quickly
and easily, including antidotes, that are only stocked in small numbers of
trusts across the area.There is also scope strategically to plan and
rationalise antidote availability at a national level.
8. Pharmacists working in
emergency care need to be familiar with the management of common poisonings
such as those caused by overdoses of paracetamol, antidepressants and hypnotics
(eg, benzodiazepines). Key aspects of good patient management include:
●
Establishing
a patient’s drug history from his or her medical notes, or from the patient (if
appropriate), including over-the-counter medicines
● Ensuring the appropriate
prescribing of, and availability of, antidotes
●
Providing
patient information
● Supporting the continuity of
medicine supply on discharge, where appropriate
Assisting medical teams in identifying the constituent
ingredients of poisonous products and unidentified medicines is another main
role for pharmacists. The TICTAC database(visual drug identification database
covering medicines),is a useful resource for the
latter.