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 of powder dosage form:
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 of powder dosage form:
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
Purified talc sterilized
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 dusting powder
|Surgical dusting powder
|They should not to be applied to open wounds and broken skin.
|These are applied to body cavities and wounds and on burns
|Sterility is rarely essential
|They contain Anti-Bacterial agent.
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.
It is used as antiseptic, Anti-pruritic, Protective, Adsorbent and lubricating.
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.
1. Not uniform dosage
2. Particles stick to each other and wall of the insufflators
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.
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.
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.
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.
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.
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.
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.
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.
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