Powders: Definition, classification, advantages and disadvantages, Simple & compound powders − official preparations, effervescent, efflorescent and hygroscopic powders, eutectic mixtures. Geometric dilutions.

1. PREPARED BY
SUJITHA MARY
ASSISTANT PROFESSOR
KVM COLLEGE OF PHARMACY

2.  The solid dosage forms are available mostly in unit dosage
forms, (consisting of doses which are taken by numbers), such
as, tablets, capsules, pills, cachets or powders.
 When drugs are to be administered orally in dry state, tablets
and capsules are the most convenient dosage form.

3.  A pharmaceutical powder is a mixture of finely divided
drug and/or chemicals in dry form.
 These are solid dosage form of medicament which are
meant for internal and external use.
 They are available in crystalline or amorphous form.
 The particle size of powder plays an important role in
physical, chemical and biological properties of the dosage
forms.

4. (1) Powders are one of the oldest dosage form and are used both
internally and externally.
2) Powders are more stable than liquid dosage form.
(3) It is convenient for the physician to prescribe a specific
amount of powdered-medicament depending upon the need of
the patient.
(4)The chances of incompatibility are less as compared to liquid
dosage form.
(5)The onset of action of powdered drug is rapid as compared to
other solid dosage form, e.g. tablets, capsules or pill

5. 6) Large quantity of powdered drugs can be easily administered
the patient orally by dissolving or mixing the powder in a
suitable liquid.
(7)Small children and elderly patients cannot swallow solid
dosage Forms, such as, tablets and capsules. They can easily
take the Powdered drug as such or dispersed in water or any
other liquid.
(8) Powders are more economical as compared to other solid
dosage form, because these are prepared without involving
any special machinery and techniques.
(9)Powders are more easy to carry than the liquid dosage forms.

6.  Drugs having bitter, nauseous and unpleasant taste cannot be
dispensed in powdered form.
 Deliquescent and hygroscopic drugs cannot be dispensed in
powder form.
 Drugs which get affected by atmospheric conditions are not
suitable for dispensing in powder forms.
 Quantity less than 100 mg or so, cannot be weighed
conveniently on dispensing balance.
 The dispensing of powder is a time consuming.

7.  Spatulation : In this method, mixing of powders is done by
the movement of a spatula throughout the powders on a
sheet of a paper or On a porcelain tile. The method is very
useful in mixing:-
(a) Small amount of powder.
(b) Solid substances that liquefy or form eutectic mixtures,
when in close and prolonged contact with one another since
very little compression or compact results.
 The method is not suitable for large quantities of powders or
for powders containing one or more potent substances
because homogenous blending may not occur.

8. 2.Trituration :
 It is used both to reduce particle size and mix powders.
 If particle size reduction is desired along with mixing of
powders, a porcelain mortar with a rough inner surface is
preferred to a glass mortar with a smooth working surface.
 A glass mortar may be preferred for chemicals that may strain
a porcelain surface and for simple mixture substances without
special need for comminution.

9. Geometric dilution :*
 The method is used when potent substances are to
mixed with a large amount of diluents.
 The potent drug is placed upon an approximately equal
volume of the dilute in a mortar and the substances
are slightly mixed by trituration.
 A second portion of diluents equal in volume to the
powder mixture in the mortar is added and trituration
is repeated.
 The process is continued, adding diluents equal in
volume to the mixture in the mortar at each step, until
all the diluent is incorporated.

10.  For example, if 100 mg of potent drug is required to be mixed with 900 mg of
lactose, then according to geometric dilution, the following Procedure should be
followed:-
100 mg of a potent drug + 100 mg of lactose = 200 mg of mixture
200 mg of the mixture + 200 mg of lactose = 400 mg of mixture
400 mg of the mixture + 400 mg of lactose = 800 mg of mixture
800 mg of the mixture + remaining portion= 1000 mg of mixture lactose

11.  4.Sifting : The powders are mixed by passing through siften
This process results in a light-fluffy product and is generally
not acceptable for incorporation of potent drugs into a
diluents base.
 5.Tumbling: Tumbling is the process of mixing powders in a
large container rotated by an electric motor. These blenders
are widely employed in industry as large volume powder
mixers.

12.  Powders may be wrapped in paper or dispensed in bulk
powder in wide mouth container
 Wrapping of powders: Weigh the required number of
powders and wrap in the papers. White glazed paper is
generally used for wrapping .The wrapping should be done on
a clean tile or large sheet of a glazed paper to protect the
product
 In a well-wrapped powder, there should be no powder within
the flaps or folds. When powder is opened, for administration,
the powdered material should appear in the centre of the paper

13.  Double wrapping White glazed paper gives inadequate
protection to volatile, hygroscopic and deliquescent substances
unless it is lined with waxed paper. The lining is cut a few mm
smaller each way than the white glazed paper and it is quite
satisfactory to fold both papers together. In exceptional cases,
each packet may be wrapped externally in aluminium foil.
 Labelling : Patient should be instructed that individual powder
should be dispersed in a little water or placed on the back of
the tongue before swallowing.

14.  Bulk powder for internal use
 Bulk powder for external use*
 Simple and compound powder for internal use*
 Powders enclosed in and capsule
 Compressed powders (tablets)

15. Powders are dispensed in bulk, when accuracy of dosage is not important.
Bulk powder contains several doses of powder. They are supplied wide-
mouthed containers that permits easy removal of a spoonful of powder. The
non potent substances which are supplied in bulk are antacids and laxatives
etc.
compound rhubarb powder B.P.C (Gregory’s Powder)
Rx
Rhubarb, in powder 250.0 g
Light magnesium carbonate 325.0 g
Heavy magnesium carbonate 325.0 g
Ginger, in powder 100.0 g
Make a powder
Method: Powder all the ingredients. Weigh and mix them in ascending order
of their weight. Transfer the powder in a Wide-mouthed Bottle and
dispense

16.  Bulk powder meant for external use are non potent substances. These
powders are supplied in cardboard, glass or plastic containers, which are
often designed for the specific method of application. The dusting powders
are preferably supplied in perforated or sifter top containers. The container
should bear a label indicating that the powder is meant for external
application.
The bulk powders which are commonly used for external applications are as
follows:-
 Dusting powder
 Insufflations
 Snuffs
 Dentifrices

17.  These are meant for external application to the skin and are
generally applied in a very fine state of sub division to avoid
local irritation. Hence, dusting powders should be passed
through sieve no. 80 to enhance their effectiveness.
Dusting powders are of two types:-
 Medical
 Surgical
 Medical dusting powders are used mainly for superficial skin
conditions
 surgical dusting powder are used in body cavities and also on
major wounds as a result of burns and umbilical cords of infants.
Surgical dusting powders must be sterilised before their use,
whereas medical dusting powders must be free from pathogenic
microorganisms.

18.  Dusting powders are generally prepared by mixing two or
more ingredients one of which must be either starch, tale or
kaolin as one of the ingredients of the formulation.
 Talc and kaolin are more commonly used because these are
chemically inert. since such ingredients are readily
contaminated with pathogenic bacteria, these must be
sterilised by dry heat method (160° for 2 hours) before their
use
 The dusting powders are dispensed in sifter-top containers or
aerosol containers.
 The pressure aerosol containers are costlier than the sifter- top
containers but they help in the easy application of the
preparation.

19.  Dusting powders are generally considered to be non-toxic but
the inhalation of its fine powdered ingredients by infants may
lead to pulmonary inflammation. So proper care must be taken
while handling these preparations.
 The dusting powders are mainly used for their antiseptic,
astringent , absorbent, antiperspirant.
Rx
Purified tale, sterilised 50.0 g
Starch, in powder 25.0 g
Zinc oxide, in powder 20.0 g
Salicylic acid, in powder 5.0g
Make a Powder

20.  Direction: Applied on the affected part two or three times a
day.
 Method: Powder all the ingredients. Weigh the required
quantity of purified talc, starch, zinc oxide and salicylic acid.
Mix them in ascending order of their weight. Pass the mixed
powder through a sieve no. 85. After sifting again mix lightly.
Transfer the powder in sifter top containers to protect it from
atmospheric contamination.

21.  These are applied with the help of a tooth brush for cleaning
the surface of the teeth.
 They contain a suitable detergent or soap, some abrasive
substance and a suitable flavour.
 The abrasive agents such as calcium sulphate, magnesium
carbonate, sodium carbonate and sodium chloride are used in
fine powder.
 A strong abrasive substance should however not to be used as
it may damage the tooth structure.

22.  In this form of powder, each individual dose is enclosed in
paper. The number of ingredients may be one (simple powder)
or more than one (compound powder). The minimum quantity
of each powder should not be less then 100 mg so that it can
be handled conveniently by patient and can be weighed
accurately.
 While dispensing simple and compound powders, following
rules should be observed.
 The ingredients after calculating for one extra powder.
 If the quantity of an ingredient is not directly weighable,
calculate for sufficient extra powders to produce directly
weighable quantity.

23.  In case of potent ingredient, calculate the amount of lactose to
be mixed to make each powder directly weighable
 Simple powder: A simple powder contains only one
ingredient either in crystalline or amorphous form. When the
powder is in crystal- line form, it is reduced to fine powder,
weighed the powder and divided into number of doses and
wrapped as individual doses

24. Rx
Aspirin 300 mg
Make powder.
Method: Powder the aspirin and weigh the required quantity of
aspirin. Weigh 300 mg of aspirin for each powder. Wrap each
dose in individual powder paper. Six such powder. Pack it flap
to flap and restrained with elastic band

25.  Compound powders: Compound powders contain two or
more than two substances which are mixed together and then
divided into desired number of individual doses which are
dispensed into each powder paper
Dispense eight powders of A.P.C.
Aspirin 300 mg
Paracetamol 150 mg
Caffeine 50 mg
Make a powder.

26. Direction: One powder to be taken when need arises.
Method: Powder all the ingredients and weigh the calculated
quantity of each ingredient. Mix them in ascending order of
their weight Weigh 500 mg of the mixed powder for each
powder. Wrap each dose in individual powder paper. Pack in
pairs flap to flap and restrained with elastic band

27.  Cachets are the solid unit dosage form of drugs. These are
moulded from rice paper, which is made by pouring a mixture
of rice flour and water between two hot, polished, revolving
cylinders.
 The water evaporates and a sheet of wafer is formed. Cachets
are used to enclose nauseous or disagreeable powders and are
available in different sizes to hold drugs from 0.2 to 1.5 g of
powder.
 Cachets are also known as wafer capsule.
 They are quite hard to swallow .

28. Cachets are of two types:-
 Wet seal cachets
 Dry seal cachets

29.  These are powders moulded into tablets. Moulded tablets are flat,
circular disc and usually contains a potent substance which is mixed
with lactose, dextrose or some other suitable diluent.
 The apparatus used for the preparation of tablet triturates is made
of stainless steel or plastic. It consists of an upper perforated plate
which is having an exactly the same number of holes as that of
number of pegs in a lower plate. The lower plate also have two large
pegs which ensure correct fitting of the plates. The moulds are
available in several sizes having a capacity ranging from 30 to 250
mg. Generally 50 to 250 tablet triturates can be prepared at a time
from a tablet triturate mould.

30. 1.Hygroscopic and deliquescent powders*
 The powders which absorb moisture from the atmosphere are
called hygroscopic powders. But certain powders absorb
moisture to such a great extent that they go into solution and
are called deliquescent powders.
 Examples of such substances include ammonium chloride,
iron and ammonium citrate, pepsin, phenobarbitone, sodium
bromide, sodium iodide, potassium citrate, zinc Chloride etc.
 Such substances are usually supplied-in-granular form in order
to expose less surface area to the atmosphere.

31.  These powders should not be finely powdered. Such powders
should be double wrapped. In humid weather or when dealing
with very deliquescent substances, further wrapping in
aluminium foil or plastic cover is advisable.

32.  Some crystalline substances liberate water of crystallisation
wholly or partly on exposure to humid atmosphere or during
trituration and thus become wet or liquefy.
 Example of such substances include caffeine, citric acid,
ferrous sulphate etc. This difficulty may be overcome by using
either corresponding anhydrous salt or an inert substance may
be mixed with efflorescent substance before incorporating
with other ingredients.

33. When an oxidising substance such as Potassium chlorate is
mixed with reducing substance, such as tannic acid, there are
chances of violent explosion which may lead to serious
consequences.
Dispense the following powder
Potassium chlorate 0.6g
Tannic acid 0.3g
Sucrose 0.3g

34.  When two or more substances are mixed together they liquefy
due to the formation of a compound which has a Tower
melting point than the individual substances. Such substances
are called eutectic substances.
 Example of such substances include menthol. Thymol,
camphor, phenol, aspirin, phenacetin, chloral hydrate
These substances can be dispensed by two methods:”-
1. Dispense as separate set of powders with directions that one
set of each kind shall be taken as a dose

35.  2. An equal amount of any of inert absorbent like magnesium
carbonate, light magnesium oxide, kaolin, starch, lactose, cal
cium phosphate etc. may be mixed with eutectic substance and
then blended together lightly with a spatula on a sheet of
paper.
 When in addition to liquefying substances, other ingredients
are also present, the liquefiable substances should first be
triturated together to form the eutectic mixture.
 Then the remaining ingredients of the prescription are
incorporated and mixed together.

36. Rx
Menthol 5g
Camphor 5g
Ammonium chloride 30g
Light magnesium carbonate 60g
Make an insufflation.
Direction: To be used as directed.
Method: Separately powder each ingredient and weigh
required quantity of menthol, camphor and ammonium
chloride. Mix them in ascending order of their weight in a
mortar to form a liquid. Add light magnesium carbonate to
make a free flowing powder. Pass the powder through
number 85 sieve and dispense the powder in an air tight
container

37.  Effervescent granules are the specially prepared solid dosage
form of medicament, meant for internal use. They contain a
medicament mixed with citric acid, tartaric acid and sodium
bicarbonate.
 Sometimes saccharin or sucrose may be added as a sweetening
agent Before administration, the desired quantity is dissolved
in the acid and bicarbonate react together producing
effervescence.
 The carbonated water produced from the release of carbon
dioxide serves to mask the bitter and saline taste of drugs.
Moreover, carbon dioxide stimulates the flow of gastric juice
and helps in the absorption of medicament

38. Method of Preparation: There are two methods of preparation of
effervescent granules:-
(1)Heat method (2) Wet method
 Heat method: A large porcelain or stainless steel evaporating
dish is placed over the boiling water bath. The dish must be
sufficiently hot before transferring the powder into it, to
ensure liberation of the water of the crystallisation from the
citric acid.
 If heating of the dish is delayed, the powder which is added to
it, will heat up slowly and the liberated water of crystallisation
will go on evaporating simultaneously. As a result, sufficient
water will not be available to make a coherent mass

39. 1.From water of crystallisation of citric acid. The citric acid
contains one molecule of water of crystallisation which is
liberated during heating.
3NaHCO3 +C6H8O7.H₂O C6H5Nа307+ 3CO2 + 3H20
2.The water produced from the reactions of citric acid and
tartaric acid with sodium bicarbonate.
2NaHCO3 + C4H606 C4H4Na2O6+ 2CO2 + 2H2O
Generally, heating stage takes 1 to 5 minutes. The damp mass
is then passed through a sieve to prepare the granules of
suitable size, dried in an oven at a temperature not exceeding
60°C and then packed in an air tight container

40.  Loss of weight occurs during granulation as a result of:-
(i) evaporation from the damp mixture.
(ii)Loss of carbon dioxide.
 These losses constitute approximately one-seventh of the
weight of powder used and must be taken into consideration
while calculating the quantity of granules to be prepared.

41.  In this method, the mixed ingredients are moistened with a
non-aqueous liquid (e.g. alcohol) to prepare a coherent mass
which is then passed a number 8 sieve and dried in an oven at
a temperature exceeding 60°C.
 The dried granules are again passed through the sieve to break
the lumps which may be formed during drying.
 The dried granules are packed in air tight containers.

42. Rx
Sodium bicarbonate, in powder 20.4 g
Tartaric acid, in powder 10.8 g
Citric acid, in powder 7.2 g
Refined sugar, in powder 6.0g
Iron and ammonium citrate 2.15 g
Make Effervescent granules