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The prescription CHAPTER 24
supplied using the endorsements ‘prescriber contacted’ and ‘prescriber not contacted’ as outlined in
the BNF.
The pharmacist should also check that the prescription is appropriate for the patient and that it
will be of benefit and not cause the patient harm. A
number of court cases have identified that the
pharmacist has a responsibility for what they have
supplied under the directions of the prescriber.
Therefore, in addition to ensuring the prescription
is legal and complete, the pharmacist should be
checking the clinical elements of the prescribing
and contacting the prescriber to discuss any issues
they have identified.
One suggested way to do this review is by using the
mnemonic IDEAL CASE, as follows:
I – nteractions
D – ose
E – vidence of harm/benefit
A – ppropriate (and here is where we make a CASE
for the medication)
L – egal and complete
C – ost-effective
A – cceptable to the patient
S – afe
E – ffective
Interactions
Does the drug interact with any other items the patient is taking or with the patient’s condition? Many of
the programmes which are used to produce labels and
store a patient’s medication record in the pharmacy
have the functionality that will identify possible interactions. The information is normally highlighted on
the computer screen in the pharmacy with an indication of the possible importance of the interaction. The
pharmacist needs to be able to interpret this information and, using any other information they have,
decide what action would be appropriate to ensure
that no harm comes to the patient.
Dose
Is the dose and dosage regimen appropriate for the
patient and their condition? (See Example 24.3.) This
is more significant when dealing with drugs that have a
narrow therapeutic window (i.e. the dose difference
between the therapeutic dose and the toxic dose is
small) and when using medication in the very young or
very old patient. Being able to calculate the appropriate dose for the patient is a key skill and will sometimes require knowledge about the weight of the
patient. Doses should be checked against the maximum dosage information contained in the BNF in the
UK. The BNF states maximum doses in a number of
ways:
*
A specific dose per day – e.g. 200 mg per day
*
A specific dose per day for a specific time – e.g.
200 mg per day for 7 days
*
A specific dose for a specific number of times per
day – e.g. 200 mg three times daily
*
A combination of the above – e.g. 200 mg per day,
in divided doses, for 15 days
Example 24.3
Look at the following details which are written on a prescription:
Elizabeth Riley
2 Black Avenue
Mediton
Bendroflumethiazide tablets 5 mg
1 tablet to be taken at night
Send 28 tablets
On the above prescription there is no indication of the age of the patient. It cannot be assumed that the patient is an adult.
If the patient is a child, then the dose may be inappropriate and the BNF for children would have to be consulted.
Bendroflumethiazide is usually taken in the morning, not at night, but night workers may take the tablets at night. In this
case it is essential to check with the patient and the prescriber for the correctness of the prescription. If the patient is
taking the medication for hypertension then the normal dose would be 2.5 mg each morning and increasing the dose will
have little enhanced effect, and this too may need to be discussed with the prescriber.
269
SECTION FOUR Dispensing and related pharmaceutical practice activities
*
An initial dose – e.g. 200 mg initially, then ...
*
A dose per kg of body weight – e.g. 250 micrograms
per kg
*
A dose per square metre of body surface – e.g.
25 mg per metre squared
*
A maximum dose – e.g. do not take more than 2
Appropriate
Is the product the most appropriate medication available for the patient and their condition? This leads
into the use of the mnemonic CASE, which helps to
look at the specifics of the drug in terms of its cost, its
acceptability to the patient and its safety and efficacy.
tablets at any one time; do not take more than 8 in
24 hours.
If the strength or dose and dosage regimen is missing
or incorrect on the prescription, the pharmacist will
have to calculate an appropriate strength, dose or
dosage regimen. The pharmacist will then have to
discuss this with the prescriber to ensure that this
meets the patient’s requirements.
The dose and dosage regimen of the medication
may be affected by other medication on the prescription, or the conditions the patient may be suffering
from. This is particularly true if they have any degree
of kidney failure, as these are the main routes of
excretion of drugs from the body.
Legal
Check the prescription complies with any laws related to the supply of medicines. The legal requirements
will be dependent on the legislation in place in the
individual country at the time of writing the prescription. For example, the Medicines, Ethics and Practice
guide covers the legislation relating to prescriptions
generated in the UK adequately for most purposes.
However, the legal requirements are likely to require
the prescription, at the very least, to be signed and
dated by the prescriber. Clearly it is the responsibility
of the pharmacist to check that the signature is genuine and the date correct.
Evidence of benefit/harm
Is there any evidence the patient is benefiting from
the treatment? Do they believe it is working and is
there any evidence that their condition is improving?
Could it be causing them any harm? Are they suffering
from any adverse effects? Is another treatment on the
prescription being used to treat these side-effects?
(See Example 24.4.)
Cost-effective
Is there a more cost-effective product? Does this
treatment offer the most cost-effective option? This
might be worth considering if a cheaper medication
has the same evidence of safety and efficacy (e.g.
comparing the use of simvastatin and atorvastatin).
Sometimes the prescriber prescribes a dose of two
Example 24.4
Examine the following details which are written on a prescription:
Elizabeth Riley
2 Black Avenue
Mediton
Ibuprofen tablets 400 mg
1 three times a day
Send 84
Simvastatin tablets 40 mg
1 tablet to be taken at night
Send 28 tablets
On the above prescription you may find after talking to the patient that the ibuprofen is being prescribed to treat muscle
pain. Muscle pain is a recognized adverse drug reaction (ADR) of a statin which the prescriber may have missed. You
would then need to discuss with the prescriber the possibility that the symptoms may be due to an ADR to the statin. This
would enable the prescriber to decide on an appropriate course of action to take which could mean undertaking further
tests on the patient to establish if it is a true ADR.
270
The prescription CHAPTER 24
10 mg tablets when it would be cheaper to provide
one 20 mg tablet.
Acceptable to the patient
Ask the patient if they can take or use the medication?
Ask if they are able to take their medication as they
are directed to take it? Try and find out if they take
their medication all the time and investigate how concordant they are. If the patient does not or cannot take
the medicine, there is little reason for it to be dispensed in the first place. Some of the considerations
might be, for example, can they swallow tablets or
would a liquid or soluble product be more acceptable?
Or, can they use their inhaler correctly? If the patient
cannot use the inhaler after effective counselling then
they should be considered for an alternative device
which they might find easier to use. Can they get into
child resistant containers? If not, could the medicine
be supplied in a device that the patient can get into?
Safe
What do I have to do to ensure the product is safe for
this patient? Which possible side-effects might they
suffer? What should they do if they suffer from these
side-effects? In some cases this will mean that they
have to return to the prescriber, but should they stop
their treatment or keep taking it until they can see the
prescriber? Do I need to tell them about any cautions
when taking the medication? (This might be telling
them about driving or operating machinery or taking
alcohol when taking their medicine.) Does the treatment need to be monitored? If so, when, how often
and how should it be monitored? When should the
treatment be reviewed and stopped? When would I
be justified in looking for a safer alternative treatment? If the patient is currently on a treatment dose,
when can that be reduced to a maintenance dose or
even stopped?
Evidence based
Is the treatment the most effective treatment available? Is the treatment evidence based? Does the
treatment concur with any available guidelines or protocols (see Chs 17 and 18)?
The use of this mnemonic and considerations of the
questions should help the pharmacist to clinically and
legally review the prescription and thereby to ensure
that the patient is being treated optimally. The phar-
macist should then deal with any issue. Some issues
will prevent the prescription from being dispensed,
such as missing information, a potential overdose and
a serious interaction. These will mean the pharmacist
has to contact the prescriber before the prescription is
sent to the next stage in the dispensing process. Some
issues can be raised with the prescriber after the prescription has been dispensed, such as issues about the
cost-effectiveness of the treatment. Ensuring the patient gets adequate counselling when the medicine is
delivered to the patient might be enough to satisfy
some of the issues, particularly in relation to information about possible side-effects and cautions in using
the medication.
Assembly of the product and
labelling
This stage involves producing a label for the product,
selecting the product from where it is stored in the
pharmacy and doing any assembly work and putting
the label onto the product. Usually trained pharmacy
technicians carry out this stage in the process and
some pharmacies have introduced dispensing robots
to select the products. The assembly work can range
from picking a patient pack from a shelf to making the
product from its ingredients. Accuracy in this stage
of the assembly process is paramount in ensuring that
the patient gets the product ordered on the prescription. Picking the wrong strength or form, or even the
wrong product, are errors that can occur at this stage.
The dispenser needs to take great care in selecting the
products because many drugs have similar names, as
outlined in Box24.2 or they may be in containers with
a similar appearance (see Ch. 9).
Box 24.2
A few products with similar names
Aldactide Aldactone
Betnesol Betnelan
Co-amilofruse Co-amilozide
Co-amoxiclav
Cardene Codeine
Daonil Danol
Gliclazide Glipizide
Nicardipine Nifedipine
Promazine Promethazine
Zocor Zoton
271
SECTION FOUR Dispensing and related pharmaceutical practice activities
At this stage of the process the dispenser may be
required to make records, either for legal purposes
such as completion of a controlled drugs register, or
as good practice, such as adding information to a patient medication record (PMR). The prescription may
need to be priced if it is a private prescription or
endorsed as required if it is an NHS prescription.
Accuracy checking the product
against the prescription
This final accuracy check is present to ensure that
there has not been an error in the dispensing process.
It is an important stage in minimizing risk to the patient. The person involved in carrying out this check
needs to work in a structured and methodical manner
without interruption to have the best chance of working effectively. Until recently the pharmacist exclusively did the final check, but more and more
accredited checking technicians are being trained to
perform this task. This will free up the pharmacist to
carry out other tasks which better match their skills,
e.g. the delivery of medicines usage reviews (MURs)
to patients (see Ch. 47).
Delivery of the product to the
patient with the appropriate
advice about the product
The final stage is to hand the product to the patient. This stage can be done b y a pharmacist or can
be delegated to anoth er membe r of staff. It is important that whoever gives the medicine to the
patient ensures the patient has all the advice they
need. T he pharmacist must be confident that the
patient can take or use their medication correctly.
The patient should be able to identify signs to tell if
the medicine is having the desired effect or is causing a problem and they should know what to do
about it. Once the prescription has been handed to
the patient, the prescription form will be filed or
sent to the appropriate place so the pharmacy
receives payment.
Information sources
When dealing with a prescription it is important that the pharmacist knows where to look for
up-to-date information relating to different aspects
involved in checking the prescription. Drugs are
continually being introduced to the market and
the indications for some drugs change, as do doses,
dosage regimens and formulations. In addition,
some drugs are removed from the market for a
variety of r easons. Prescribers will need independent, accessible and unambiguous reviews of effective treatments when writing prescriptions, while
pharmacists will require similar information to clinically check the prescription and advise the patient.
In addition the dispenser will also need information
relating to the cost of the medication to the patient
and any rules which they must apply to ensure
appropriate remuneration and reimbursement, as
well as inf ormation about the availability and
where to order the products. Some of the most
useful information sources in the UK are listed
in Box 24.3 (see also Ch. 23 for more detailed
information).
The BNF is published and updated every
6 months and lists the products available for dispensing in the UK. It is sent to all doctors, pharmacists and prescribing nurses in the NHS. The Nurse
Prescribers’ Formulary and Dental Practitioners’
Formulary are included in the BNF and are also
published as separate booklets. There is also a
BNF for Children which has been produced to provide sound up-to-date information on the use of
medicines for treating children. The BNF is the
major source of easily available information on the
characteristics of individual medicines, including
proprietary and generic formulations, strengths,
dose and dosage regimens, drug side-effects and
Box 24.3
Some of the reference sources most
frequently used in dispensing
British National Formulary (BNF)
Medicines, Ethics and Practice Guide
Stockley’s Drug Interactions
Drug and Therapeutics Bulletin
Drug Tariff
MeReC Bulletin
Effective Healthcare
Prescribers’ Journal
Pharmaceutical Codex
Current Problems in Pharmacovigilance
Martindale: the Extra Pharmacopoeia
272
The prescription CHAPTER 24
drug interactions. The most recent copy should
always be used. For more compr ehensive information about medicines you should refer to
Martindale.
The Royal Pharmaceutical Society of Great Britain
(RPSGB) produces the Medicines, Ethics and Practice
guide. It outlines the legal requirements for the sale
and supply of medicines and poisons in the UK and
contains the RPSGB Code of Ethics for Pharmacists
and Pharmacy Technicians.
The Drug Tariff is the resource which details the
rules for the NHS remuneration and reimbursement
for pharmacy contractors in the UK and contains information on what is or is not allowed on NHS prescriptions.
If the pharmacist cannot find the information that
they require in the reference sources they have available, they can contact the local medicines information
department which will be listed in the BNF, or the
manufacturer of the product where appropriate.
KEY POINTS
*
Prescriptions are paper or electronic documents
issued by an authorized prescriber for an individual
patient
*
Prescriptions detail the medicinal treatment
required for the patient and may be paper based or
electronic
*
Prescriptions can be written by a number of
people and may be private or NHS prescriptions
and may be for GSL, POM or P medicines
*
Prescriptions can contain more than one
prescription item
*
Prescriptions must contain adequate information
before they can be dispensed
*
All prescriptions should be checked for clinical and
patient appropriateness before assembly and
dispensing
*
This is best achieved by working methodically to
ensure no items are overlooked
*
Access to reference sources is often required
273
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Chapter Twenty-Five
Dispensing techniques (compounding
and good practice)
Judith A. Rees
25
STUDY POINTS
*
Good dispensing practice to ensure quality
*
The working environment and procedures
*
Extemporaneous dispensing equipment and its
correct use, including:
T Weighing equipment
T Measuring liquids
T Mixing and grinding equipment
T Heating equipment
*
Manipulative techniques used in dispensing and
compounding
*
Ingredients and their selection
*
Problem solving in extemporaneous dispensing
*
Methods of counting tablets and capsules
Introduction
This chapter deals with some of the practical aspects
of good pharmacy practice. It will concentrate on the
small-scale manufacture of medicines from basic
ingredients in the community or in hospital pharmacy.
This process is called compounding or extemporaneous dispensing. In addition, good practice which
applies to all aspects of dispensing will be considered.
In modern practice, most medicines are manufactured by the pharmaceutical industry under well controlled conditions and packaged in suitable containers
designed to maintain the stability of the product
(e.g. sealed in an inert atmosphere). Therefore, extemporaneous dispensing, which cannot be as well
controlled, should only be used when such products
are unavailable. Reasons for unavailability of products
may include:
*
Non-licensed products
*
Products no longer on the market or unavailable
from the manufacturer, e.g. due to low demand or
superseded by newer formulations/drugs
*
Products requiring an individualized dose,
e.g. paediatric or geriatric patients
*
Products requiring an individualized formulation
for a patient, e.g. the replacement of arachis oil by
an inert oil for a patient allergic to arachis (peanut)
oil or the removal of certain ingredients such as
colouring agents
*
Veterinary products, e.g. special formulations for
different species.
The pharmacist undertaking extemporaneous dispensing has a responsibility to maintain equipment
in working order, ensure that the formula and dose
are safe and appropriate and that all materials are
sourced from recognized pharmaceutical manufacturers. There are also requirements concerning calculations, maintaining good records and labelling
regulations. Any staff involved in the process should
be adequately trained. These requirements should all
be incorporated within standard operating procedures
(SOPs).
It is important to remember in any dispensing process that the end product is going to be used or taken by
a person or an animal. It is therefore important that the
medicine produced is of the highest achievable quality.
This, in turn, means that the higheststandards must be
applied during the preparation process. If we expect
quality assurance procedures to be important in the
pharmaceutical manufacturing industry then the same
careful attention to detail must be applied to smallscale production, i.e. extemporaneous dispensing.
SECTION FOUR Dispensing and related pharmaceutical practice activities
The working environment and procedures
Organization
The working environment has a considerable influence
on a worker’s efficiency. However, an individual worker, such as a dispenser, can improve efficiency and safe
working by developing a tidy and organized method
of working. For example, a dispensing bench cluttered
with several containers all containing different ingredients makes selection of the correct ingredient more
difficult and more prone to error. Ingredients should
always be returned to their appropriate shelf/cupboard when the required quantity has been measured
out. Thus a safe system of working is essential for a
dispensary and the development and use of SOPs
should be followed. Additionally, health and safety
regulations must be applied in the dispensary.
Cleanliness/hygiene
The dispensing bench, the equipment and utensils,
and the container which is to hold the final product
must all be thoroughly clean. Lack of cleanliness can
cause contamination of the preparation with other
ingredients. For example, a spatula which has been
used to remove an ingredient from one container will
adulterate subsequent containers if not washed before being used again. Cleanliness will also minimize
microbial contamination.
Similarly dispensing staff should have a high standard of hygiene and hand washing facilities should be
readily available. Hence, a clean white overall should
be worn and be kept fastened up since open overalls
are a potential safety hazard. Open overalls may result
in clothes becoming stained if any spillages occur.Hair
should be tied back and preferably covered with a
disposable hat/cap and any skin lesions covered with
a dressing. Disposable gloves should be worn during
preparative work and discarded afterwards. Consideration should be given to the use of masks if volatile
substances or fine powders are to be handled.
formula and any calculations, the ingredients and
quantities used, their sources, batch numbers and
expiry date. All calculations or weights/volumes
should be checked by two people and recorded. Any
substances requiring special handling techniques or
hazardous substances should be recorded with the
precautions taken. The record for a prescribed item
should also include the patient and prescription
details and date of dispensing. A record must be kept
of the personnel involved, including the responsible
pharmacist.
All SOPs should be available and adhered to. Any
deviations from a SOP should be recorded.
Equipment
Not only is the selection of the correct equipment or
‘tools’ for the job essential, but the tools must also be
used in the correct way and maintained in good order
to ensure performance is unimpaired.
Weighing equipment
Nowadays, weighing equipment can be divided
into non-automatic and automatic weighing equipment. Non-automatic weighing equipment requires
an operator to place and/or remove the items from
the balance pan. Such weighing equipment can be a
mechanical beam balance, which has a pan on one end
of the beam for weights and a pan on the other end of
the beam for the material to be weighed (Fig. 25.1)or
it can be an electronic top-pan balance, in which case
the substance to be weighed is placed on the pan and
an electronic display gives the weight. Automatic
weighing equipment is designed to automatically fill
a package to the required weight without the intervention of an operator. Such equipment is used in the
pharmaceutical industry, but unlikely to be used for
extemporaneous dispensing. Whichever type of
weighing equipment is used, it must be suitable for
its intended use and be sufficiently accurate. In the
UK, weighing equipment must be calibrated in metric
units and must be marked with maximum and minimum weights that can be weighed.
Documenting procedures
and results
Keeping comprehensive records is an essential part of
the dispensing process. Records must be kept for a
minimum of 2 years (ideally 5 years) and include the
276
General rules for the use and maintenance
of weighing equipment
Balances can give incorrect readings because of poor
practice or misuse. The following points are important to ensure accurate weighing:
Dispensing techniques (compounding and good practice) CHAPTER 25
Figure 25.1*Dispensing balance.
*
It is important to use balances on a level surface:
most will incorporate a level indicator device, so
make sure it reads level before trying to adjust for a
zero balance display.
*
Balances must be correctly balanced before
use, with any indicators reading zero. On
electronic balances the display should indicate
zero, not b e blank. If zero is not indicated then
incorrect readings, and hence weights, may be
obtained.
*
Strong draughts, caused by air conditioning or a
breeze as a result of doors or windows being open,
can affect some balances and make a correct
reading impossible. Therefore always site a balance
in a draught-free area.
*
Always keep the balance pan clean and free from
debris underneath the balance pan itself.
Build-up of debris can interfere with the
weighing operation.
*
Regular checks with stamped weights should
be made to ensure the balance is working
correctly.
*
If possible keep a record of when, and by whom,
the check was carried out as well as the result.
*
Never weigh less than the declared minimum
weight or more than the maximum weight declared
on the balance.
Use of a beam balance
As well as the above, the following ‘rules’ apply to the
use of a beam balance:
*
Ensure that the balance and pans are clean.
*
Check that the pointer is swinging freely.
*
Remove the appropriate weights, using the
tweezers provided, and place them on the left-hand
pan. (Never handle weights, as this will affect their
accuracy and risks contamination.)
*
Immediately close the lid of the weight box or close
the drawer containing the weights after removal
of the weights. If it is left open there is a possibility
that ingredients to be weighed will fall into the box/
drawer, contaminating the weights and affecting
their accuracy.
*
A solid material to be weighed should then be
placed carefully onto the right-hand scale pan. Do
not weigh ingredients on a piece of paper as this
introduces a potential inaccuracy. The exception is
when weighing greasy or semi-solid materials,
e.g. white soft paraffin, when a counterbalanced
piece of paper should be used.
*
When the correct weight has been achieved the pan
should be carefully removed from the balance and
the material transferred to a suitable container.
*
Errors in this transference stage may occur if care is
not taken to ensure that all the weighed material
has been removed from the scale pan. If the drug is
to be dissolved or incorporated into a suspension, it
can be washed from the scale pan using some of the
appropriate liquid vehicle.
*
Tapping the glass pan against the side of the
container can cause it to become chipped. This will
affect the accuracy of the balance and slivers of
glass will not improve the health of the patient!
*
The balance pan should then be washed and dried
thoroughly, before any further substance is
weighed. A second substance must never be
weighed on the remains of the first.
*
The weights should be returned to the box/drawer.
Use of top-pan balance
*
Ensure that the balance is level, in a draught-free
environment and working properly.
*
Place an appropriate container (such as a weighing
boat) or piece of paper on the pan and use the
auto-zero to cancel its weight.
*
Add the material to be weighed until the correct
weight is shown on the display.
277
SECTION FOUR Dispensing and related pharmaceutical practice activities
*
Carefully remove the weighed material as above.
In addition to using the balance correctly there are
one or two other rules which should be observed
when weighing, to ensure good dispensing practice.
These are:
*
If using a solid material that requires size reduction
by grinding or sieving, always ensure that this
procedure is carried out before weighing the
required quantity. If a quantity of powder is
weighed and then size reduced by grinding in a
mortar or sieving, there is a strong possibility that
some of the material will be lost in the process and
the final preparation will not contain the correct
proportions of ingredients. The best approach is to
roughly weigh an excess quantity, grind or sieve it as
required, then accurately weigh off the required
quantity.
*
As far as possible never split quantities and do two
weightings, as this will increase the inaccuracies.
*
If a quantity less than the legal minimum is needed,
it is necessary to weigh the minimum weight
Figure 25.2*Conical dispensing measure.
allowable (or more) and make an excess of the
product or prepare it by trituration (see Ch. 35).
*
The measure is thoroughly drained. Even if the
Measuring liquids
Liquid measures
All measures for liquids must comply with current
weights and measures regulations and should be
stamped accordingly. Traditionally, conical measures
(Fig. 25.2) have been used in dispensing, although, if
not used carefully, they can be less accurate than
cylindrical measures.
Whichever type of measure is chosen, always ensure the following:
*
The level of liquid is read to the bottom of the
meniscus.
*
The measure is vertical when reading the meniscus.
If this is not done, considerable errors in quantities
can occur, especially with conical measures, where
the error increases with height because of the slope
of the sides.
ingredient is only slightly viscous, it is amazing how
much can be left in the measure.
*
As far as possible, never use more than one
measure. Splitting the volume between two
measures increases the potential for error.
*
Always select the smallest measure which will hold
the desired volume, because this gives the greatest
accuracy. For example, use a 10 mL measure to
measure 5 mL; do not use a 20 mL measure.
*
If the su bstance being measured is so viscous that
it would be very difficult to drain the measure
effectively, then the volume s hould be measured
by difference. This is done by pouring an
excess into the measure and then pouring off
the liquid until only the excess volume remains
(see Example 25.1).
When measuring liquids it is important to observe
two simple rules which ensure g ood dispensing
practice:
Example 25.1
25 mL of glycerol is required.
Because of the viscosity it is difficult to remove it
completely from the measure.
278
It is therefore advisable to measure, say, 35 mL and pour
off the 25 mL required, ensuring that 10 mL is left in the
measure. Remember to allow sufficient time for the liquid
to drain back down.