Dispensing Techniques

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Dispensing Techniques

• Compounding and Good Practice

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Compounding (Extemporaneous Dispensing)

• Definition A small-scale manufacture of
  medicines from basic ingredients in the community
  or in hospital pharmacy ( vs. medicines
  manufactured by the pharmaceutical industry).
• Extemporaneous dispensing should only be used
  when medicines are not available commercially in
  the market
• Low demand.
• Requires an individualized dose, e.g. paediatric.
• Requires an individualized formulation for a
  patient.

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The working environment

• Organization
• Cleanliness
• The bench, the equipment, utensils the
  container. Lack of cleanliness can cause
  contamination of the preparation with other
  ingredients or a microbial contamination.
• Appearance
• A clean white overall, closed, hair tied
  up.
• Documenting procedures and results
• Keeping comprehensive records for a minimum of 2
  years (ideally 5 years) and include the formula,
  the ingredients and quantities used, their
  sources, batch numbers and expiry date.
• The record for a prescribed item should also
  include the patient and prescription details and
  date of dispensing.
• Methodical approach.

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EQUIPMENT

• Weighing
• Non-automatic and automatic weighing equipment.
• Non-automated dispensing balances include
  mechanical beam and electronic top-pan balances.
• Three types of balances have traditionally been
  used in dispensing class A (50mg to 1g), class B
  (the most commonly used 100mg to 50g), and class
  C (1g to 2kg).
• Class B prescription balances are designed for
  the weighing of medicinal or pharmaceutical
  substances required in filling of prescriptions
  or in a small scale compounding. (Also known as
  Class B dispensing balance).

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EQUIPMENT
Torbal torsion balance ( class B) and Ohaus
electronic balance.
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EQUIPMENT
Set of metric weights
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EQUIPMENT

• When weighing, some important rules to ensure
  good dispensing practice
• Use balances on a level surface (level indicator
  device).
• Balances must be balanced before use, with any
  indicators reading zero.
• Keep the balance in a draught-free environment,
  clean and free from debris.
• When using a top-pan balance, an appropriate
  container (weighing boat) or piece of paper and
  auto-zero to cancel its weight.
• If using a solid material which requires to be
  size reduced (ground) or sieved, always ensure
  that this is carried out before weighing 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 allowable (or more) and make an excess of
  the product or prepare it by trituration.

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EQUIPMENT

• B. Measuring liquids
• Liquid measures Conical measures and cylindrical
  measures.
• Measuring small volumes by small conical measure
  (min. measurable vol for a 10 mL conical is 1
  mL), by graduated pipettes (5 mL to 0.1mL), and
  by trituration (for smaller volumes).

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EQUIPMENT

• The level of liquid is read to the bottom of the
  meniscus.
• The measure is vertical when reading the
  meniscus if not considerable errors in
  quantities can occur especially with conical
  where the error increases with height because of
  the slope of the sides.

Volume error differentials due to instrument
diameters
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EQUIPMENT

• Never use more than one measure ? increases
  error.
• Select the smallest measure that will hold the
  desired volume.
• The measure is thoroughly drained (material can
  be left in the measure).
• If the substance being measured is so viscous
  ?difficult to drain the measure effectively ?
  measurement by difference (pouring excess into
  the measure and then pouring off the liquid until
  only excess volume remains).
• Rules for good dispensing practice (label
  position and the cap of the container).

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EQUIPMENT

• C. Mixing Grinding
• Mortar and pestle
• Glass mortar and pestle
• Used for small quantities Useful for dissolving
  small quantities of ingredients, for mixing small
  quantities of fine powders
• Suitable for size reduction of friable materials
  (such as crystals).
• Used for the mixing of substances such as dyes
  which are absorbed by and stain composition or
  porcelain mortars.

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EQUIPMENT

• Porcelain or composition mortars and pestles
• Larger than the glass variety and have a rougher
  surface.
• Ideal for size reduction of solids and for mixing
  solids and liquids, as in the preparation of
  suspensions and emulsions.

• For size reduction select proper type.
• For mixing purposes
• sufficient space is required for adequate mixing
• Rotate pestle in both directions

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EQUIPEMENT

• Filters
• Filters are used when clarification of a liquid
  is required.
• Filter paper
• Filter paper has the disadvantages of introducing
  fibers into the filtrate and may also absorb
  significant amounts of active ingredient. Such
  disadvantages are less likely to happen with the
  following types.
• Membrane filters
• Sintered glass filters
• These do not shed fibers, are easy to clean and
  can be used for substances which attack filter
  paper such as potassium permanganate and zinc
  chloride.
• A filter with a pore size 1540 µm (grade 3) is
  suitable for most solutions. They will pass
  through by gravity, although large volumes may be
  slow and need the assistance of a vacuum. A grade
  4 filter (pore size 515 µm) requires a vacuum.

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Filters
Sintered glass filter
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EQUIPMENT

• D. Heat Sources
• Bunsen (gas) burners

The Bunsen burner, used for heating laboratory
equipment and chemicals. The flame can reach
temperatures of 1,500C/2,732F and is at its
hottest when the collar is open.
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EQUIPMENT

• Water-baths These are used when melting ointment
  bases or preparing suppositories
• Electric hot plates Used for melting and heating
  and have the advantage of thermostatic controls.

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Manipulative techniques

• Correct equipment Appropriate technique Good
  Compounding Practice
• Mixing
• The goal of any mixing operation should be to
  ensure that even distribution of all the
  ingredients has occurred.
• Mixing of liquids Simple stirring or shaking
  (the degree depends on the viscosity of liquids).
• Mixing solids with liquids stirring rod
  (solution), pestle and mortar (suspension).
  Consider size reduction to speed up dissolution
  process or enhance the distribution of solid
  through out the liquid.
• Mixing solids with solids mortar and pestle,
  doubling up procedure.
• Mixing semi-solids
• rubbing them on an ointment slap using a spatula
  (may need doubling up).
• The fusion method using a porcelain evaporating
  basin.

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Manipulative techniques

• Tared containers
• For what purpose?
• How to tare a bottle?

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SELECTION OF INGREDIENTS

• Reputable supplier.
• Good storage conditions.
• Check on expiry dates.
• Variety of forms.
• Synonyms.

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SELECTION OF INGREDIENTS

• Variety of forms

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Selection of ingredients

• Synonyms

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Concentrated waters

• Liquid preparations for oral use are often
  flavored to make them more palatable for the
  patient. In extemporaneously prepared products
  the flavoring is frequently a flavored water,
  e.g. peppermint water, aniseed water.
• All concentrated waters have the same dilution
  factor, i.e. 1 part of concentrate plus 39 parts
  of water to give 40 parts of flavored water.

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PROBLEM SOLVING INEXTEMPORANEOUS DISPENSING

• Official preparations
• The application of simple scientific knowledge
  physical properties.
• Solubility are the ingredients soluble in the
  main vehicles, the particle size, are they
  present in a lumpy or granular form. If the
  substance is not soluble, a suspension or an
  emulsion where one material is an oil will be
  produced.
• Volatile ingredients
• Viscosity
• Expiry date.
• e.g. The following prescription is received
• Sodium Bicarbonate Ear Drops BP, Send 10 mL.
• Formula
• Sodium bicarbonate 500 mg (sol 1 in 11 of
  water)
• Glycerol 3 mL (viscous liquid)
• Freshly boiled and cooled water to 10 mL
  (quantity of water in ear drops is app. 6.5 mL)

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COUNTING DEVICES For Tablets and Capsules

• Various methods can be used for this counting
• The manual method.
• A counting triangle (for pills) and capsule
  counter are the best.
• A perforated counting tray.
• An electronic counter Electronic balances,
  Photoelectric cell counters.
• medicines must not be touched by hand.
• The equipment should also be carefully cleaned
  before use.

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Counting triangle
http//iforg.com/blog/?p17
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Capsule counter
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Perforated Counting Tray
http//www.adelphi-coldstream.uk.com/products/phar
macyl-dispensing-equipment/tablet-capsule-counters
/tumatic-capsule-counter.html
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Key Points

• Extemporaneous dispensing should only be used
  when manufactured medicines are not available.
• Accurate dispensing requires clean, neat
  methodical work.
• Comprehensive records of extemporaneous
  dispensing are required to be kept for at least 2
  years.
• Electronic balances are increasingly being used
  in extemporaneous dispensing.

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Key Points

• Do not use a balance to weigh less than its
  minimum weighable quantity.
• Ensure that liquid measures comply with the
  Weights and Measures Regulations.
• Always use the bottom of the meniscus when
  measuring liquids.
• Viscous liquids should be measured by
  difference.
• Pipettes are used to measure volumes between
  0.1 mL and 5 mL.

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Key Points

• Select the smallest measure for the volume of
  liquid to be measured.
• A glass mortar and pestle can be used for size
  reduction of friable materials and mixing small
  quantities of fine powder.
• A porcelain mortar and pestle is used for
  larger quantities, for mixing solids and liquids,
  making emulsions and for size reduction.
• Doubling-up is used for mixing a small
  quantity of powder with a larger quantity.

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Key Points

• Confusion can arise with different forms of the
  same material and the use of synonyms.
• Concentrated waters are diluted 1 part with 39
  parts of water for use as single strength.
• Simple problem-solving techniques can produce a
  satisfactory method of dispensing a product.
• Tablets and capsules can be counted manually,
  or by using a triangle, capsule counter, counting
  tray or an electronic counter.
• Tablets and capsules should not be counted in
  the hand.