Dispensing of Solution
By Maniz JoshiB.Pharmacy 7th SemesterHOPE International
CollegeSatdobato, Lalitpur, NepalDispensing of Solution and
mixture
IntroductionEssentially a solution is a homogeneous liquid
preparation that contains one or more dissolved medicaments.
Since,by definition, active ingredients are dissolved within the
vehicle, uniform doses by volume may be obtained without any need
to shake the formulation.This is an advantage over some other
formulation types, e.g. suspensions.They are of particular use for
individuals who have difficulty in swallowing solid dosage forms
(for example, paediatric, geriatric, intensive care and psychiatric
patients),
Solutions can be formulated for different routes of
administration
Orally: Syrups, elixirs, drops
In mouth and throat: Mouth washes, gargles, throat sprays.
In body cavities: Douches, enemas, ear drops, nasal sprays.
On body Surfaces: Collodions, lotions.
Composition
1) VehicleThe vehicle is the medium in which the ingredients of
a medicine are dissolved or dispersed.Water is a commonly used
vehicle.For aqueous solutionPurified Water Must be used for most
pharmaceutical operations and in all the tests and assays. Such
water is prepared by distillation, deionization or reverse osmosis.
"Hard" waters are those that contain the Ca and Mg cations.
Alkaline" waters are those that contain bicarbonates as the major
impurity.Ultraviolet energy, heat or filtration (Millipore
filtration) can be used to remove or kill the microorganisms
present in the water.
Water for injectionMust be used for the formulation of parental
solutions.It is obtained by sterilizing pyrogen-free distilled
water.
For non aqueuous solutionAromatic Waters Aromatic waters
(medicated waters) are clear, saturated aqueous solution of
volatile oils or other aromatic or volatile substances. They are
used principally as flavored or perfumed vehicles. Volatile oils
solutions represent an incompatibility problem of salting out. This
occurs after the incorporation of a very soluble salt in their
solution. Aromatic water will deteriorate with time therefore:-
should be made in small quantities - protected from intense light
and excessive heat by storing in air tight, light resistant
containers. If they become cloudy or otherwise deteriorate; they
should be discarded. Deterioration may be due to volatilization,
decomposition or mould growth.Eg: Anise water, camphor water,
peppermint water, chloroform water etc.
Adjuncts
BuffersTo resist any change in pHIsotonicity modifiers are
necessary forSolutions for injectionApplication to mucous
membraneLarge-volume solutions for ophthalmic application Most
widely used isotonicity modifiers are: dextrose and NaClViscosity
enhancerIt is difficult for aqueous-based topical solutions to
remain on the skin or in the eye therefore low concentrations of
jelling agents are added to increase the viscosity of the
product.
Chemical StabilizersThey are anti oxidants. Eg: sodium sulphite,
ascorbic acid, propyl or octyl esters of gallic acid.For eg: A
solution of ferrous sulphate contains 0.1% ascorbic acid to prevent
oxidation of ferrous to ferric ion.
ColorsDifferent colors can be added for easy identification of
oral product while other solutions (Parenteral, Opthalmic) do not
need colors.
FlavoursThe flavouring agents used in solution include-Aromatic
waters - eg: Anise waterSyrup and/or glycerol for sweetening
childrens preparationLiquorice liquid extract for disguising the
taste of saline ingredients, such as ammonium salts and alkali
iodides in cough mixtures.Lemon spirit to cover the taste of
alkaline citratesOrange Syrup to disguise the metallic and
astringent tastes of iron salts in childrens mixture.
PreservativeDiluted vegetable extracts and flavouring agents
provide favourable media for the growth of bacteria, and,
particularly, fungi and hence, an antimicrobial preservative is
often necessary in solution.The two most commonly used compounds
are: Chloroform (0.25% v/v)Benzoic Acid (0.1% wiv)The activity of
benzoic acid is due to the acidic character of benzoic acid hence
it is effective only below pH of 5 and is ineffective at the pH
above 5 (Neutral and alkaline pH).
General method1. Write out the formula either from the
prescription (unofficial) or from an official text (official).2.
Calculate the quantities required for each ingredient in the
formula to produce the required final volume. 3. Prepare a suitable
label.4. Weigh all solids.
5. Identify the soluble solids and calculate the quantity of
vehicle required to dissolve the solids fully. If more than one
solid is to be dissolved, they are dissolved one by one, in order
of solubility (i.e. the least soluble first). In almost all cases,
dissolution will take place in a glass (or occasionally plastic)
beaker, not a conical measure. Remember that the solubility of the
soluble solids will be dependent on the vehicle used.6. Transfer
the appropriate amount of vehicle to a glass beaker.
7. If necessary, transfer the solid to a glass mortar and use
the glass pestle to reduce particle size to aid dissolution.
8. Transfer the solid to the beaker and stir to aid dissolution.
If a mortar and pestle have been used to reduce particle size,
ensure that the mortar is rinsed with a little vehicle to ensure
complete transfer of the powders.9. When all the solid(s) has/have
dissolved, transfer the solution to the conical measure that will
be used to hold the final solution.10. Rinse out the beaker in
which the solution was made with a portion of the vehicle and
transfer the rinsings to the conical measure.
11. Add any remaining liquid ingredients to the conical measure
and stir.12. Make up to final volume with remaining vehicle.13.
Transfer to a suitable container, label and dispense to the
patient.
MixtureAmixtureis aliquidpreparation intended
fororaladministration in which drugs may bedissolved,suspendedor
dispersedin a suitable vehicle. Generallyseveral dosesare contained
in a bottle.Classification: Mixtures may be classified as
follows:1.Simple mixtures2.Mixtures containing diffusible
solids3.Mixtures containing indiffusible solids4.Mixture containing
precipitate forming liquids
1. Simple mixtureA simple mixture is one that contains only
soluble ingredients.
Method of dispensing(a)The solid substances are dissolved in
3/4thvolume of the vehicle.(b)The solution is examined against
light for any foreign particle. If foreign particles are present
then the solution is passed through cotton wool. Little vehicle is
poured through the cotton wool to wash down any drug present in the
wool.(c)Liquid ingredients, if any, are added and mixed.(d)More
vehicle is added to produce the final volume.(e)The mixture is
transferred to a bottle, capped tightly, polished and labeled.
Container: Narrow mouthed, screw capped, colorless, plain
bottle.Label: The ink used in the labelBlack.Special instructions:
None
2. Mixture containing diffusible solids
Diffusible solids are those, which are not soluble in water, but
on shaking they can be mixed with it and remain evenly distributed
throughout the liquid for a sufficiently long time. So dose
transfer is uniform.However, on standing the insoluble solids
settle at the bottom. Whenever a dose is taken the bottle should be
shaken to redisperse the solid.Examples of diffusible solids:
Bismuth carbonate, light kaolin, magnesium oxide, magnesium
carbonate, magnesium trisilicate etc.Method of dispensing(a)All the
solid ingredients are powdered in a mortar and mixed
thoroughly.(b)Small amount of vehicle is added to the powder and
triturated to form a smooth paste.(c)More volume of the vehicle is
added.(d)If foreign particles are present then the mixture is
strained though a muslin cloth.(e)Liquid ingredient, if any, is
added and the volume is produced with the vehicle.(f)The mixture is
transferred to the bottle.Container: Narrow mouthed, screw capped,
colorless, plain bottle.Label: The ink used in the
labelBlack.Special instruction: SHAKE WELL BEFORE USE
3. Mixture containing indiffusible solids
Indiffusible solids are those substances, which are not soluble
in water and they do not uniformly distribute throughout the
vehicle. Even after shaking they settle quickly, therefore it
becomes difficult to measure the dose accurately. In this type of
mixture a suspending agent is used that increases the viscosity of
the vehicle and thus reduces the rate of settling of the
particles.Examples of indiffusible solids: Chalk powder, acetyl
salicylic acid etc.Examples of suspending agents: Compound
tragacanth powder, Tragacanth mucilage, tragacanth powder.Method of
dispensing(a)Indiffusible, diffusible powders and calculated amount
of suspending agent are triturated in a mortar.(b)Small mount of
vehicle is added to the powder and triturated to make a smooth
paste.(c)More amount of the vehicle is added. Strained through a
muslin cloth if any foreign particle is present.(d)Liquid
ingredient, if any, is added. Volume is made up with the rest of
the vehicle.(e)The mixture is transferred to the bottle, capped,
polished and labeled.
Container: Narrow mouthed, screw capped, colorless, plain
bottle.Label: The ink used in the labelBlack.Special
instruction(s): SHAKE WELL BEFORE USE
4. Mixture containing precipitate forming liquid
Some liquid preparations contain resinous matter that is
precipitated on addition of water. This precipitates sticks to the
container and forms clots.To disperse this type of liquid first a
protective colloid is dispersed in vehicle and then the precipitate
forming liquid is added with constant stirring. The resinous
particles are coated with the protective colloid.
Examples of precipitate forming liquids:Compound benzoin
tinctureBenzoin TinctureLobelia ethereal tinctureMyrrh tinctureTolu
TinctureExamples of suspending agents: Compound tragacanth powder,
Tragacanth mucilage
Method of dispensing by using Compound tragacanth powder(a)Any
insoluble solid is powdered in a mortar and mixed with compound
tragacanth powder. Small amount of the vehicle is added to form a
smooth paste. The volume is produced to 50% of the final volume
with the vehicle.(b)The precipitate forming liquid is taken in a
dry measuring cylinder and is added to the suspension slowly, while
the suspension is stirred rapidly. The gum particles coat the
resinous particles and give a hydrophilic property to the resin
particles.(c)If any electrolytes are there it should be added only
after the resin particles are completely coated with gum, otherwise
heavy clotting will take place.(d)Strained it necessary and volume
is made up with vehicle.(e)The mixture is transferred to the
bottle, capped, polished and labeled.
Method of dispensing by using Tragacanth mucilage
(a)Mucilage is taken and added with equal volume of vehicle in a
beaker.(b)The precipitate forming liquid is measured in a dry
measuring cylinder and added into the center of the mucilage with
constant stirring.(c)If electrolyte is present, it is diluted with
vehicle and then mixed with the mucilage.(d)The mixture is
strained, if required, and the volume is produced with
vehicle.(e)The mixture is transferred to the bottle, capped,
polished and labeled.
Container: Narrow mouthed, screw capped, colorless, plain
bottle.Label: The ink used in the labelBlack.Special
instruction(s): SHAKE WELL BEFORE USE
Any Queries?
ReferenceDispensing for pharmaceutical students (COOPER AND
GUNNS)Pharmaceutical Compounding and Dispensing (CHRIS LANGLEY AND
DAWN BELCHER)Dispensing of Solutions by Dr. Muhammad
Akbarhttp://4my5959.blogspot.com/
