POWDER
Powder is solid dosage form containing
homogeneous mixtures of drugs and chemicals in a dry, fine state of
sub-division and meant for internal and external use.
Advantages:
1. Powders show a greater stability
than liquid dosage form. Ex: Aspirin and penicillin.
2. Easy of administration.
3. Rapid therapeutic effect.
4. They are easier to carry than
liquids.
5. Incompatibility is less in case of
powder than liquids.
6. Physician has free choice of drug
combination.
7. The dose variation depending on the
condition of the patient is possible.
Disadvantages:
1. Volatile drugs are not suitable for
dispensing in powder from.
2. Hygroscopic drugs cannot be
dispensing in the powder from.
3. Powder may easily deteriorate on
exposure to atmosphere because of large surface area.
4. Powder show physical instability.
Ex: colour change.
5. Time consuming to prepare.
6. Drugs which have bitter taste
cannot be dispensed in powder form.
Classification of powder:
1. Bulk powder for internal use: Powders are dispensed in bulk for which accuracy of dosage is not
important. Bulk powder contains several dosages of powders, they are supplied
in a wide mouth container. The non potent substances which are supplied in bulk
are antacid and laxative.
Ex: Compound
Rhubarb powder B.P.C
Rx: Rhubarb,
in powder
Light magnesium carbonate
Heavy magnesium carbonate
Ginger in powder
2. Bulk
powder for external use:
Bulk powder meant for external use is
non potent substances. These powders are supplied in cardboard, glass or
plastic containers, which are often designed for specific method of
application.
1) Dusting powders: Dusting
powders are mixtures of two or more medicaments, in a dry fine state of
subdivision meant for external use.
Ex-Compound dusting powder of Zno and H3Bo3
Rx: Zno
Boric acid
Starch
Purified talc sterilized
Properties:
1. Homogenous
2. No local irritation
3. Flow easily
4. Spread uniformly
5. Cling to the skin
6. Good covering capability
7. Good adsorptive and absorptive capacity
8. Capable to protect the skin against irritation by friction, moisture
or chemical irritants.
Method
of preparation: Finely powder all the ingredients and
mix them in an ascending order of weight, pass the powder through sieve No.250
in order to remove gritty particles. The dusting powder must be homogeneous and
in a very fine state of subdivision to enhance effective and minimize local
irritation.
Dusting
powders are divided into two types.
|
Medicated |
|
|
They should not to be applied to |
These are applied to body cavities |
|
Sterility is rarely essential |
They contain Anti-Bacterial agent. |
Containers:
The dusting powders are dispensed in
sifter-top containers or pressure aerosols. The pressure aerosol containers are
costlier than other containers but can protect the medicaments from
contamination and other atmospheric conditions and help in the easy application
of the preparation.
Uses:
It is used as antiseptic, Anti-pruritic,
Protective, Adsorbent and lubricating.
2. Insufflations: These
are finely divided dusting powders meant for introduction into the body
cavities such a Ear, Nose, Tooth sockets, Throat, Vagina etc. It is applied by
insufflators consists of bulb chamber and delivery nozzle. Powder is placed in
chamber and when bulb is compressed the air current carries the fine particles
through the nozzle to cavities it produce local as well as systemic effects.
Disadvantages:
1.
Not uniform dosage
2.
Particles stick to each other and wall of the insufflators
3. Snuffs: For
local action, these are to be inhaled through the nose. They are packed in a
metal box or enclosed in a double wrapper lined with a waxy paper.
Ex: anti-septic powders.
4. Dentifrices: Dentifrices are used to clean the teeth they should have cleaning
action by the detergent property. They should not damage tooth structure.
They
contain following ingredients:
a. Mild abrasive and polishing agents:
Ex -CaCo3, prepared chalk
b. Detergents: Ex – sodium lauryl sulphate
c. Anti-septic: Ex – Phenol.
d. Preservatives: Ex -sodium benzoate
e. Flavouring agents: Ex- menthol,
peppermint oil
f. Sweetening agent: Ex-saccharine.
3. Simple and compound powder for
internal use:
a) Simple powder: A
simple powder contains only one ingredient.
b) Compound powder:
A compound powders contain two or more than two ingredient.
4. Powder Enclosed In cachets: Cachets
or rice flour capsules are dosage containers formed by sealing together two
concave discs of wafer sheet. The sizes varied from 3/4 to 1/8 inch in
diameter. The medicament is filled in one concave disc. The other disc is
placed over the medicament filled disc. The two discs were tightly sealed by
moistening the margins and pressing together firmly. Cachets are allowed to
float on water so that they became soft, elastic and slippery. They could be
swallowed with a cup of water. It should be protected from light.
Advantages:
1. Easy to prepare no complicated machinery is
required.
2. Drugs are quickly dispensed in cachets.
3. Large doses of drugs can be dispensed.
4. They disintegrate quickly in the stomach.
Disadvantage:
1. They are easily damaged.
2. They do not protect the enclosed drugs from
light and moisture.
3. They require moistening before swallowing.
4. They cannot be filled by large scale
machinery.
5. The shell of cachets are fragile. So that
drug contents cannot be compressed in cachets.
5. Compressed powders (Tablet triturate):
Tablet triturates are disc like masses
moulded powders weighing 30mg to 250mg each prepared by the process of
moulding. It consists of active medicament and bases.
It
is prepared by taking required quantity of the drug is mixed with a little
quantity of the diluent. This mixture is moistened with moistening agent and
the wet mass is pressed into the perforations of the mould. If the mass is too
wet shrinkage will occur. If mass is not properly wetted then the mass will not
have proper cohesion to make a firm tablet. These are prepared by using hand
moulding machine.
Powders requiring
special consideration:
1. Eutectic powder: When two organic substances having low melting points are brought
in physical contact with one another they may from a liquid or a semi-solid
mass.
The liquefaction may be due to
lowering the melting points in presence of impurities. When two substances are
brought in contact each may act as impurity for the other. It results in
lowering of melting points of the both ingredient. If the melting point lowered
to below the room temperature ingredients liquefies.
Ex: The combination of any two of the following camphor, menthol,
thymol, phenol, salicylic acid, acetyl salicylate, phenol salicylate, chloral
hydrate.
Remedy:
1. If the eutectic combination is
known each ingredient is mixed with an inert substances like starch, lactose, MgCo3, then mixed the both and dispensed each ingredient in
separate enclosures.
2. If the combination is not known
allow liquefy then add the adsorbent like lactose or starch or MgCo3 to get in the form of
powder.
2. Effervescent Granules: Certain crystalline substances liberate water
of crystallisation wholly or partly due to change in humidity or during
triturations. As the result the powder becomes wet or liquefy.
Importance of ingredients:
1.
NaHCo3: It reacts with
acids, when the preparation is added to water the liberated Co2 produces effervescence.
2.
Citric acid:
i)
Provide water from crystallization and form partial interaction.
ii)
Neutralize NaHCo3,It
neutralizes remaining NaHCo3.
3.
Tartaric acid: It neutralize remaining NaHCo3
4.
Medicaments: For therapeutic action, it should be
anhydrous and soluble in water. In many cases the medicament is an in-organic
salt.
5.
Sugar: It acts as sweetening agent to mask
bitter taste.
Method of preparation: It is prepared by two methods they are:
1. Heat
method or fusion method
2. Wet
method.
Heat method:
1.
Place a porcelain
dish on water bath the disk should be deep in water bath. Heat the bath to the boiling point.
2.
All the
ingredients are powdered, passed through sieve No-250, weighed and mixed them
by ascending order.
3.
Place all the
powders in the hot porcelain dish on the boiling water bath.
4.
Press the powders
with a stainless steel spatula until it forms a loose cake or a damp coherent
mass. It takes about 1-5 minutes.
5.
Remove the dish
from the water bath. The damp mass is passed through a sieve No-8 to get
granules.
6.
Granules are
dried in an oven at a temperature less than degree 60.
7.
The granules are
then packed in wide mouthed and airtight containers.
Wet
method:
1.
Powdered each
ingredient, weighed and mix them.
2.
Mixed ingredients
are moistened with alcohol with continuous stirring until a coherent mass is
formed.
3.
The mass is
passed through sieve No-250 to obtain granules.
4.
These granules
are dried in an over below 60 degree.
5.
Dried granules
are again passed through sieve no-8 to break the lumps which may have been
formed during drying.
6.
Dried granules
are packed in dry, wide mouthed and air tight container.
Containers:
Screw capped wide mouthed bottle or plastic
jar.
Auxiliary
label: Store in a cool and dry place.
What are the possible errors in weighing?
1.
If the balance is
not kept on a uniform surface.
2.
Before weighing
the chemicals two equal weights of paper should be placed on both sides of the
pan, if the weight of two papers is un-equal than error may occur.
3.
If the small
amount of the potent drug adheres to the paper, than error may be possible.
4.
Spoilage of the
powder may be possible during weighing and transferring of the material from
the paper to the appropriate container.
5.
Errors may be
possible. If wear and tear on the bearings and corrosion of knife edges.
Geometric Dilution:
When the prescribed dose of the
medicament is very small quantity (0.5-2.0). It cannot be weighed accurately in
a dispensing balance. So a suitable triturate is prepared by mixing the
medicament with diluents in order to increase the bulk so that it can be
weighed correctly. This method is known as geometric dilution method.
1.
In this method,
small quantity of the drug is mixed with equal quantity of the diluents.
2.
Total weight of
this powder mixture is again mixed with same weight of the diluents.
3.
This process is
repeated as many times as possible until all the powder is mixed.
4.
The main
advantage of geometrical dilution is that the concentration of the active medicament is uniformly distributed in each
dose.
Ex: Lactose
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