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Pharmaceutical calculations CHAPTER 26
KEY POINTS
*
Always work methodically and write down
calculations clearly
*
Check calculations, using a different method where
possible
*
Estimate the answer before you start
*
Try to visualize the quantities you are using in the
calculation
*
Look carefully to see if a formula gives the
quantities of all ingredients or uses ‘to’ for the
vehicle
*
Equations can be a useful way of carrying out
calculations, but care is required to ensure that the
correct figures are being used
*
Always check the units being used and be careful
not to mix them during a calculation
*
Be very careful to read the wording; small changes
in terminology can alter the calculation
*
Triturates with solids and liquids normally use a 1 in
10 dilution per step
*
Be very careful in checking doses, particularly with
‘in divided doses’ and ‘mg/kg’ statements in the
reference books
*
On completion of a calculation, ask yourself
whether the answer is ‘reasonable’ given the
numbers you are using
Self-assessment questions
(Express answers to 2 decimal places where appropriate.)
1.1 Express 20 grains in grams.
1.2 Express 300 p.p.m. as a percentage strength.
1.3 Express 324 mg in grains.
1.4 What is the total volume to be dispensed when
the prescription states:
5 mL three times daily for 2/52?
1.5 Calculate the number of tablets to be dispensed
when the prescription states:
2 tablets four times daily for 2/52.
1.6 Calculate the volume of and total quantity to be
dispensed for a prescription for a drug which is
available as a 250 mg/5 mL syrup:
100 mg twice daily for 3/52.
2.1 Express the following as percentages (indicating
w/w, w/v, v/v, where appropriate):
a 1 g in 220 mL of solution
b 110 mg of sodium chloride in 100 mL of
solution
c 0.3 mL in 2.5 mL of solution
d 2 g in 630 g of solution
e 50 mg of sodium chloride in 120 mL
f 2 L of drug in 5000 mL of solution
g 3600 parts per million
h 1 in 4000 solution
i 170 mg of potassium chloride in 90 mL
j 0.15 mL in 13 mL
k 2 g in 630 mL
l 100 microgram/5 mL
m 1.2 mg/mL.
2.2 Express 0.025% w/w as 1 part in ...
2.3 The following are examples of concentrations
expressed as percentages. Indicate the amount
of drug present in:
a 90 mL of 1.3% w/v solution
b 15 mL of 4.2% w/v preparation
c 2 L of a 0.05% v/v preparation
d 50 mL of 3.2% w/v preparation
e 75 g of a 0.6% w/w mixture
f 150 mL of a 0.002% w/v preparation.
2.4 What weight of lactose is required to make
80 mL of 3.0% w/v solution?
2.5 How much drug is required to prepare 50 g of a
0.3% w/w mixture?
2.6 Express 0.4% w/v as mg/mL.
2.7 How many milligrams of drug are there in 5 mL
of 2% w/v solution?
2.8 Calculate the number of milligrams of the
following compounds to be dissolved in 1 L of
aqueous solution to give a concentration of
10 mmol:
(Atomic weights: H = 1, C = 12, N = 14,
O = 16, S = 32, Cl = 35.5, K = 39)
a Hydrochloric acid (HCl)
b Sulphuric acid (H
2SO4
)
c Potassium chloride (KCl)
d A drug with the molecular formula
ONCl.
C
12H12
2.9 Express 222 mg of calcium chloride (CaCl
)in
2
2 L of solution as millimoles.
(Atomic weights: Ca = 40, Cl = 35.5)
2.10 How many grams of aspirin (C
9H8O4
) are
contained in 1 millimole?
2.11 How many mmol are there in 15 g of
tetracycline hydrochloride (C
22H24N2O8
HCl)?
3.1 What weight of each ingredient is required for
the extemporaneous preparation if 50 g of the
following preparation is to be made?
299
SECTION FOUR Dispensing and related pharmaceutical practice activities
Hydrocortisone 10 g
Oxytetracycline 30 g
Wool fat 100 g
White soft paraffin 860 g
3.2 Calculate the quantities for the following
prescriptions:
a White beeswax 20 g
Hard paraffin 30 g
Cetostearyl alcohol 50 g
Soft paraffin 900 g
Prepare 150 g
b Light magnesium carbonate 3 g
Sodium bicarbonate 5 g
Aromatic cardamom tincture 3 mL
Chloroform water, double
strength 50 mL
Water to 100 mL
Send 120 mL
3.3 Calculate the quantities required for the
following extemporaneous preparations:
a Ichthammol 5 parts
Cetostearyl alcohol 3 parts
Wool fat 10 parts
Zinc cream to 100 parts
Send 120 g
b Chlorhexidine gluconate 20%
solution 5 parts
Cetomacrogol emulsifying wax 25 parts
Liquid paraffin 10 parts
Water to 100 parts
Send 30 g
c Zinc oxide 6 parts
Arachis oil 7 parts
Wool fat 2 parts
Water to 20 parts
Send 60 g
d Wool alcohols 6%
Soft paraffin 10%
Hard paraffin 24%
Liquid paraffin 60%
Send 30 g
e Menthol 2%
Eucalyptus oil 10%
Light magnesium carbonate 7%
Water to 100%
Send 150 mL
f Cetrimide 3%
Cetostearyl alcohol 13.5 g
White soft paraffin 25 g
Liquid paraffin to 50 g
Send 150 g
g Starch 7 parts
Zinc oxide 8 parts
Olive oil 2 parts
Wool fat 3 parts
Send 30 g
h Cetomacrogol emulsifying wax 60 g
Benzyl alcohol 3 g
Methyl paraben 2.3%
Water to 200 g
Send 40 g
i Cetrimide 3%
Cetostearyl alcohol 13.5 g
White soft paraffin 25 g
Liquid paraffin to 50 g
Send 40 g
4.1 How much cetrimide is required to make
30 mL of a solution which, when 1 mL is
diluted to 100 mL, produces a 100 parts per
million solution?
4.2 What percentage is produced when 200 mg of
powder is made up to 40 g with a diluent?
4.3 What concentration is produced when 75 mL of
an 8% solution is diluted to 3 L?
4.4 What concentration is produced when 200 mL
of a 1 in 40 solution is diluted to 1000 mL?
4.5 What concentration is produced when 75 mL of
a 1 in 12.5 solution is diluted to 500 mL?
4.6 What weight of drug must be added to 100 g of
2% ointment to produce a 3.5% ointment?
4.7 Sulphur ointment is available as 5% w/w and 8%
w/w. Calculate the quantities needed to
prepare 60 g of 6% w/w ointment.
4.8 Orphenadrine syrup is available as 25 mg/
5 mL and 50 mg/5 mL. Calculate the
quantities to use to prepare 1000 mL of
45 mg/5 mL syrup.
4.9 What weight of drug must be added to 50 g of
2% ointment to produce a 3% ointment?
4.10 Calculate the amount of drug and 2.5% w/w
ointment to make 60 g of 3.5% ointment.
4.11 How much of a 0.5% solution is required so that
when diluted to 600 mL it produces a 1 in 8000
solution?
4.12 What volume of normal saline (0.9% w/v NaCl)
can be made from 1.5 g NaCl?
4.13 What volume of 0.8% solution can be made
from 300 mL of 2.5% solution?
300
Pharmaceutical calculations CHAPTER 26
4.14 What volume of 2% solution can be made from
225 mL of 5% solution?
4.15 What volume of 0.5% solution can be made
from 300 mL of 1 in 40 solution?
4.16 How many grams of ichthammol must be added
to an ointment base to produce 150 g of a 0.13%
w/w ichthammol?
4.17 Calculate the weight of drug which must be
added to 1 litre of a 17% w/v solution (density
1.2 g/mL) to make a 20% w/w solution.
4.18 Calculate the volume of 4% solution of
cetrimide to prepare 600 mL of a 1 in 1000
solution.
4.19 Calculate the volume of 2% of potassium
permanganate required to prepare 1 L of a
0.01% solution.
4.20 Calculate the volume of 1 in 20 solution of
chlorhexidine to prepare 250 mL of a 0.2%
solution.
5.1 Calculate how to make 30 120 mg powders,
each containing 0.5 mg of colchicine.
5.2 Calculate how to make 10 120 mg powders,
each containing 2 mg of carbachol.
5.3 Calculate how to make 20 120 mg powders,
each containing 0.4 mg of atropine sulphate.
5.4 Calculate how to make 20 120 mg capsules,
each containing 0.6 mg of hyoscine
hydrobromide.
6.1 How much water is required to dissolve:
a 5 g of aspirin (solubility 1 in 300)?
b 50 mg of morphine sulphate (solubility 1 in
21)?
c 40 mg of hydralazine hydrochloride
(solubility 1 in 25)?
6.2 How much lithium carbonate will dissolve in
20 mL of water (solubility 1 in 100)? If 300 mg
is to be dispensed, will it dissolve in 20 mL of
water?
6.3 300 mg quinine hydrobromide (solubility 1 in
55) is to be dispensed; will it dissolve in 30 mL
of water?
6.4 A drug has a solubility 1 in 50 of water and 1 in
14 of alcohol.
a Will 250 milligrams dissolve in 4 mL of
water?
b Will 4 g dissolve in 60 mL of alcohol?
c Will 10 micrograms dissolve in 0.002 mL of
water?
d Will 1 kg dissolve in 3 L of alcohol?
e Will 0.05 g dissolve in 0.2 mL of alcohol?
7.1 For the following prescriptions calculate the
dose of active ingredient which the patient
will be taking on each occasion and each
day.
a Sudafed elixir
Mitte 150 mL
Sig. 3 mL t.i.d.
(Sudafed elixir contains pseudoephedrine
30 milligrams/5 mL.)
b Codeine linctus half strength
Mitte 200 mL
Sig. 2.5 mL t.i.d.
(Codeine linctus contains codeine phosphate
15 milligrams/5 mL.)
c Ketotifen elixir
Mitte 300 mL
Sig. 7.5 mL b.i.d.
(Ketotifen elixir contains ketotifen
1 milligram/5 mL.
d Alimemazine syrup forte
Mitte 150 mL
Sig. 10 mL b.i.d.
(Alimemazine syrup forte contains
alimemazine tartrate 30 milligrams/
5 mL.)
7.2 For the following prescriptions calculate the
volume of liquid which the patient will take on
each occasion.
a Loratadine syrup
Mitte 500 mL
Sig. 8 milligrams daily
(Loratadine syrup contains loratadine
5 milligrams/5 mL.)
b Methadone oral concentrate is available as
20 mg/mL. What volume is required to
provide 2 mg, 17 mg, 43 mg?
c Promethazine elixir
Mitte 100 mL
Sig. 12 milligrams daily
(Promethazine elixir contains promethazine
hydrochloride 5 mg/5 mL.)
7.3 What dose of atenolol should be given to a
patient weighing 75 kg to provide a dose of
150 micrograms/kg?
7.4 Calculate the dose of cisplatin to provide
60 mg/m
area 1.57 m
2
for a patient of estimated surface
2
.
301
SECTION FOUR Dispensing and related pharmaceutical practice activities
8.1 What is the weight of antibiotic in a 5 mL dose
when a bottle containing 15 g antibiotic is made
up with water to give 150 mL of syrup?
8.2 What is the total volume, after adding water to
15 g of antibiotic, to provide a 250 mg dose per
5 mL dose?
8.3 The label on a bottle of ampicillin syrup
indicates that 92 mL of water should be added
to make 100 mL of syrup. How much water
should be added to produce 130 mL of syrup?
8.4 An injection of amphotericin B contains 50 mg/
10 mL. What volume must be added to 500 mL
of normal saline infusion to produce a
1200 microgram/mL solution?
9.1 An infusion solution contains 5 g in 500 mL.
What rate of infusion should be used to give
16 mg/min? How long will a 500 mL infusion
last?
9.2 In preparing an IV infusion, you have a solution
containing 2 g/mL furosemide (molecular
weight 330.7). What volume must be added to a
500 mL infusion to provide a 12 mmol total
dose?
10.1 Paregoric is 4% v/v tincture of opium which is
10% w/v opium. If opium contains 10% w/w
morphine what weight of morphine is contained
in a 30 mL bottle of Paregoric?
2.1l 0.0020% w/v
2.1m 0.12% w/v
2.2 1 in 4000
2.3a 1.17 g
2.3b 0.63 g
2.3c 1 mL
2.3d 1.6 g
2.3e 0.45 g or 450 mg
2.3f 0.003 g or 3 mg
2.4 2.40 g
2.5 0.15 g or 150 mg
2.6 4 mg/mL
2.7 100 mg
2.8a 365 mg
2.8b 980 mg
2.8c 745 mg
2.8d 2215 mg
2.9 1 mmol
2.10 0.18 g or 180 mg
2.11 31.22 mmol
3.1
Hydrocortisone 0.5 g
Oxytetracycline 1.5 g
Wool fat 5 g
White soft paraffin 43 g
Self-assessment answers
1.1 1.30 g
1.2 0.03%
1.3 5 grains
1.4 210 mL
1.5 112 tablets
1.6 A 2 mL dose and a total of 84 mL to be
dispensed
2.1a 0.45% w/v
2.1b 0.11% w/v
2.1c 12% v/v
2.1d 0.32% w/w
2.1e 0.04% w/v
2.1f 40% v/v
2.1g 0.36%
2.1h 0.03%
2.1i 0.19% w/v
2.1j 1.15% v/v
2.1k 0.32% w/v
302
White beeswax 3 g
3.2a
Hard paraffin 4.5 g
Cetostearyl alcohol 7.5 g
Soft paraffin 135 g
Light magnesium
3.2b
carbonate 3.6 g
Sodium bicarbonate 6.0 g
Aromatic cardamom
tincture 3.6 mL
Chloroform water,
double strength 60 mL
Water to 120 mL
Ichthammol 6 g
3.3a
Cetostearyl alcohol 3.6 g
Wool fat 12 g
Zinc cream to 120 g
3.3b
Chlorhexidine
gluconate 20%
solution 1.5 g
Cetomacrogol
emulsifying wax 7.5 g
Liquid paraffin 3 g
Water to 30 g
Pharmaceutical calculations CHAPTER 26
3.3c
Zinc oxide 18 g
Arachis oil 21 g
Wool fat 6 g
Water to 60 g
3.3d
Wool alcohols 1.8 g
Soft paraffin 3 g
Hard paraffin 7.2 g
Liquid paraffin 18 g
3.3e
Menthol 3 g
Eucalyptus oil 15 mL
Light magnesium
carbonate 10.5 g
Water to 150 mL
3.3f
Cetrimide 4.5 g
Cetostearyl alcohol 40.5 g
White soft paraffin 75 g
Liquid paraffin 30 g
3.3g
Starch 10.5 g
Zinc oxide 12 g
Olive oil 3 g
Wool fat 4.5 g
3.3h
Cetomacrogol
emulsifying wax 12 g
Benzyl alcohol 0.6 g
Methyl paraben 0.92 g
Water 26.48 g
3.3i
Cetrimide 1.2 g
Cetostearyl alcohol 10.8 g
White soft paraffin 20 g
Liquid paraffin 8 g
4.1 0.3 g
4.2 0.5% w/w
4.3 0.2%
4.4 0.5%
4.5 1.2%
4.6 1.55 g
4.7 5% ointment 40 g, 8% ointment 20 g
4.8 25 mg/5 mL 200 mL, 50 mg/5 mL 800 mL
4.9 0.52 g
4.10 Drug 0.62 g, Ointment 59.38 g
4.11 15 mL
4.12 166.67 mL
4.13 937.5 mL
4.14 562.5 mL
4.15 1500 mL
4.16 195 mg or 0.2 g
4.17 The weight of drug to be added = 87.50 g
17% w/v solution = 14.167% w/w
Weight of 1 litre of 17% w/v solution is 1200 g
4.18 15 mL
4.19 5 mL
4.20 10 mL
5.1 Weigh 100 mg drug, dilute with 900 mg
lactose, take 150 mg of mixture and mix with
3.450 g of lactose to give 3.6 g total and divide
into 30 120 mg separately wrapped
powders.
5.2 Weigh 100 mg drug, dilute with 900 mg
lactose, take 200 mg of mixture and mix with
1.000 g of lactose to give 1.2 g total and divide
into 10 120 mg separately wrapped
powders.
5.3 Weigh 100 mg drug, dilute with 900 mg
lactose, take 100 mg of mixture, di lute
with 900 mg lactose, take 800 mg of
second mixture and mix with 1.600 g
of lactose to give 2.4 g total and divide
into 20 120 mg separately wrapped
powders.
5.4 Weigh 100 mg drug, dilute with 900 mg
lactose, take 120 mg of mixture and mix with
2.280 g of lactose to give 2.4 g total and divide
into 20 120 mg separately wrapped
powders.
6.1a 1.5 L or 1500 mL
6.1b 1.05 mL
6.1c 1 mL
6.2 0.2 g or 200 mg. No, because 300 mg of
lithium carbonate requires 30 mL of water in
which to dissolve.
6.3 Yes
6.4a No, because 250 milligrams of drug requires
12.5 mL of water in which to dissolve.
6.4b Yes, because 4 g of drug requires 56 mL of
alcohol in which to dissolve.
6.4c Yes, because 10 micrograms of drug requires
0.0005 mL of water in which to dissolve.
6.4d No, because 1 kg of drug requires 14 L of
alcohol in which to dissolve.
6.4e No, because 50 milligrams of drug requires
0.7 mL of alcohol in which to dissolve.
7.1a 18 mg per dose, 54 mg per day
7.1b 3.75 mg per dose, 11.25 mg per day
7.1c 1.5 mg per dose, 3 mg per day
7.1d 60 mg per dose, 120 mg per day
7.2a 8 mL of the syrup
7.2b 2 mg in 0.1 mL, 17 mg in 0.85 mL, 43 mg in
2.15 mL
303
SECTION FOUR Dispensing and related pharmaceutical practice activities
7.2c 12 mL of the elixir
7.3 11.25 mg
7.4 94.2 mg
8.1 0.5 g or 500 mg
8.2 300 mL
8.3 122 mL
8.4 120 mL
9.1 1.6 mL/min, 313 min (5 h 13 min)
9.2 1.98 mL
10.1 12 mg
304
Chapter Twenty-Seven
Packaging
Derek G. Chapman
27
STUDY POINTS
*
Definition of a container
*
Considerations made in selecting a container
*
The difference between primary and secondary
packaging
*
The materials used for packaging, including glass,
plastics, metal and paper
*
Types of container in common use
*
Child-resistant closures and tamper-evident seals
*
Patient pack dispensing
Introduction
Pharmaceutical formulations must be suitably contained, protected and labelled from the time of manufacture until the patient uses them. Throughout this
period the container must maintain the quality, safety
and stability of the medicine and protect the product
against physical, climatic, chemical and biological
hazards. The British Pharmacopoeia identifies the
closure as part of the container.
To promote good patient compliance the container
must be user friendly. This is particularly significant
for the elderly who have to take more medicines than
the general population and have a greater need for
improved compliance (see Ch. 46). Thus containers
should be easy to open and reclose, most notably for
elderly or arthritic patients. However, other factors
must also be considered in the selection of the container used to package a pharmaceutical formulation,
including the cost and the need for both childresistant closures and tamper-evident seals.
Repackaging is performed in the community
pharmacy for dispensing purposes (see Chs 25
and 36), in hospital pharmacy and in specialized
production facilities. Bulk medicines are repackaged into smaller quantities in dispensing containers
for distribution to hospital wards, clinics and
general practitioners for direct supply to patients.
This is mostly carried out with tablets and capsules
that are transferred from bulk quantities into smaller
amounts that are more suitable for patient use. In
the UK this process is performed in the hospital
pharmacy where the Medicines and Healthcare
products Regulatory Agency (MHRA) allows the
repackaging of small batches of up to 25 containers.
Larger batches must be packed in licensed manufacturing premises. The facilities used for these repackaging operations are designed to maintain the quality of
the medicine and avoid product contamination and
mix up.
Medicines originally contained in patient packs
are subdivided into small amounts by transferring
small quantities of the medici ne in strip or blister
packs into secondary cardboard containers. The
composition of containers and closures used for
the repackaging of bulk medicines must be carefully selected and must be of a quality as good as the
original container. Both glass and plastic containers
are used for repackaging but glass containers are
often preferred due to the more inert qualities of
glass.
Primary containers used for repackaging must not:
*
Allow product leakage
*
Chemically react with the product
*
Release components
*
Uptake product components.
The container used in the repackaging process must
protect the product from:
SECTION FOUR Dispensing and related pharmaceutical practice activities
*
Physical damage
*
Chemical and microbial contamination
*
Light, moisture and oxygen as appropriate.
As the medicine has been transferred into a new container, the expiry date of the repackaged medicine
must not exceed 12 months unless the stability of
the repackaged product justifies a longer shelf life.
The details of these repackaging processes must be
recorded.
Each container of the repackaged batch is labelled
with the:
*
Identity and quantity of the medicine
*
Batch number
*
Appropriate storage instructions
*
Product expiry date
*
Requirements for handling and storage.
There are some situations where the repackaging is
limited, such as with glyceryl trinitrate tablets, owing
to the potential loss of the volatile drug (see Ch. 36).
Sterile products cannot easily be repackaged and require effective closure systems to minimize the risk of
microbial contamination of the contents within the
container. In addition, the pack itself must withstand
sterilization procedures. Consequently, care must be
applied to the selection of the container and its
closure for the packaging of sterile products (see also
Chs 38, 39, 40 and 41).
Primary and secondary packaging
extraneous chemical and microbial contamination.
In addition, the primary packaging should support
use of the product by the patient. Secondary packages
are additional packaging materials that improve the
appearance of the product and include outer wrappers
or labels that do not make direct contact with the
product (Table 27.1). Secondary packages can also
supply information about the product and its use.
They should provide evidence of tampering with the
medicine.
The following terms are used to describe containers:
Single-dose containers hold the medicine that is
intended for single use. An example of such a
container is the glass ampoule.
Multidose containers hold a quantity of the material
that will be used as two or more doses. An example
of this system is the multiple dose vial or the plastic
tablet bottle.
Well-closed containers protect the product from
contamination with unwanted foreign materials
and from loss of contents during use.
Airtight containers are impermeable to solids,
liquids and gases during normal storage and use.
If the container is to be opened on more than one
occasion it must remain airtight after reclosure.
Sealed containers such as glass ampoules are closed
by fusion of the container material.
Tamper-evident containers are closed containers
fitted with a device that irreversibly indicates if
the container has been opened.
Light-resistant containers protect the contents
Primary packaging materials are in direct contact with
the product. This also applies to the closure, which is
also part of the primary pack. It is important that this
container must not interact with the medicine. It
must protect the medicine from damage and from
from the effect of radiation at a wavelength
between 290 nm and 450 nm.
Child-resistant containers, commonly referred to as
CRCs, are designed to prevent children accessing
the potentially hazardous product.
Table 27.1 Types of primary and secondary packaging materials and their use
Material Type Examples of use
Glass Primary Metric medical bottle, ampoule, vial
Plastic Primary Ampoule, vial, container, infusion fluid dropper bottle
Plastic Secondary Wrapper to contain primary pack
Board Secondary Box to contain primary pack
Paper Secondary Labels, patient information leaflet
306
Packaging CHAPTER 27
Strip packs have at least one sealed pocket of
material with each pocket containing a single
dose of the product. The pack is made of two
layers of film or laminate material. The nature
and the level of protection that is required by the
contained product will affect the composition of
these layers.
Blister packs are composed of a base layer, with
cavities that contain the pharmaceutical product,
and a lid. This lid is sealed to the base layer by
heat, pressure or both. They are more rigid than
strip packs and are not used for powders or
semi-solids. Blister packs can be printed with
day and week identifiers to produce calendar
packs. These identifiers will support patient
compliance.
Tropicalized packs are blister packs with an
additional aluminium membrane to provide
greater protection against high humidity.
Pressurized packs expel the product through a valve.
The pressure for the expulsion of the product is
provided by the positive pressure of the propellant
that is often a compressed or liquefied gas (see
Ch. 37).
Original packs are pharmaceutical packs that are
commercially produced and intended for finite
treatment periods. These packs are dispensed
directly to the patient in their original form.
Manufacturer’s information is contained on the
pack but the pharmacist must attach a dispensary
label.
An important consideration when selecting the
packagi ng for any product is that its main objective
is that the package must contribute to delivering a
drug to a specific site of effective activity in the
patient.
The selection of packaging for a pharmaceutical
product is dependent on the following factors:
*
The nature of the product itself: its chemical
activity, sensitivity to moisture and oxygen,
compatibility with packaging materials
*
The type of patient: is it to be used by an elderly or
arthritic patient or by a child?
*
The dosage form
*
Method of administering the medication
*
Required shelf life
*
Product use, such as for dispensing or for an over
the counter product.
See also Chapter 36 in Pharmaceutics: the Science of
Dosage Form Design.
Packaging materials
Glass
Historically, glass has been widely used as a drug
packaging material. It continues to be the preferred
packaging material for many pharmaceutical products.
Glass does have several advantages:
*
It is inert to most medicinal products
*
It is impervious to air and moisture
*
It allows easy inspection of the container contents
*
It can be coloured to protect contents from
harmful wavelengths of light
*
It is easy to clean and sterilize by heat
*
It is available in variously shaped containers.
The disadvantages of glass include:
*
It is fragile: glass fragments can be released into the
product during transport or contaminants can
penetrate the product by way of cracks in the
container
*
Certain types of glass release alkali into the
container contents
*
It is expensive when compared to the price of
plastic
*
It is heavy resulting in increased transport costs.
The chemical stability of glass for pharmaceutical use
is given by the resistance of the glass to the release of
soluble minerals into water contacting the glass. This
is known as the hydrolytic resistance. Details are given
in the British Pharmacopoeia (2007) for three types of
glass.
Type I glass
This is also known as neutral glass or borosilicate glass.
It possesses a high hydrolytic resistance due to the
chemical composition of the glass. It is the most inert
type of pharmaceutical glass with the lowest coefficient of thermal expansion. As a result, it is unlikely
to crack on exposure to rapid temperature changes.
Type I glass is suitable for packing all pharmaceutical
preparations. However, it is expensive and this
restricts its applications. It is widely used as glass
ampoules and vials to package fluids for injection. In
addition, it is used to package solutions that could
dissolve basic oxides in the glass. This would increase
the pH of the formulation and could affect the drug
stability and potency.
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SECTION FOUR Dispensing and related pharmaceutical practice activities
Type II glass
This is made of soda-lime-silica glass with a high hydrolytic resistance due to surface treatment of the
glass. Type II glass is used to package aqueous preparations. In general, it is not used by manufacturers to
package parenteral formulations with a pH less than 7.
This glass has a lower melting point than Type I glass.
It is thus easier to produce and consequently cheaper.
It is the glass used to produce containers for eye preparations and other dropper bottles.
Type III glass
This is made of a soda-lime-silica glass. It has a similar
composition to Type II glass but contains more leachable oxides. Type III glass offers only moderate resistance to leaching and is commonly used to produce
dispensary metric medical bottles. It is also suitable
for packaging non-aqueous parenteral products and
powders for injection.
Figure 27.2*Ribbed oval bottle.
Types of glass containers
Bottles
These are commonly used in the dispensary as either
amber metric medical bottles or ribbed (fluted) oval
bottles. Both types of bottle are available in sizes
from 50 mL to 500 mL and are supplied with a screw
closure.
Amber metric medical bottles have a smooth
curved side and a flat side (Fig. 27.1). The bottle
was designed to permit the curved side of the bottle to fit into the palm of the hand when pouring from
Figure 27.1*Metric medicine bottle.
the bottle. The flat side was intended to permit the
attachment of a label. In practice, however, the label
is commonly attached to the curved surface of the
bottle. Amber metric medical bottles are used for
packaging a wide range of oral medicines.
Ribbed oval bottles have flutes down one side of
the container (Fig. 27.2). The characteristic feel
of the flutes warns the user that the contents are
not to be taken. A label is attached to the plain front
of the bottle. Ribbed oval bottles are used to package
various products that should not be taken orally; this
includes liniments, lotions, inhalations and antiseptic
solutions.
Dropper bottles
Eye drop and dropper bottles for ear and nasal use are
hexagonal-shaped amber glass containers fluted on
three sides. They are fitted with a cap, rubber teat
and dropper as the closure. The bottles are used at a
capacity of 10 mL or 20 mL. The label is attached to
the plain sides of the bottle.
Jars
Powders and semi-solid preparations are generally
packed in wide-mouthed cylindrical jars made of
clear or amber glass. The capacity of these jars varies
from 15 mL to 500 mL. Ointment jars are used for
packing extemporaneously prepared ointments and
pastes. They are also used to repackage commercial
products where microbial contamination by the
patient’s fingers is not detrimental to the product.
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