B. Pharm Powders and Its Classifications

Definition, Advantages and Disadvantages

1. POWDERS Ms. Chitralekha G. Therkar Assistant Professor Dept. of Pharmaceutics, Siddhivinayak College of Pharmacy, Warora

2. Introduction Pharmaceutical powders are solid dosage form of medicament in which one or more than one drug is dispensed in finely divided state with or without excipients. Pharmaceutical powders = Powdered API + Dry powdered excipients They can be used for both internal and external routes of administration based on the use of it. They are available in crystalline as well as amorphous form , crystalline form indicates the regular internal structure with repeating unit whereas the amorphous form indicates irregular internal structure . There is relationship between particle size of powder, dissolution, absorption and therapeutic effect of drug. The particle size of powders is generally ranges from 10000 micron – 0.1 micron.

3. Advantages It can be used both internally and externally . Powdered dosage forms are very convenient for children and elderly patients as they can be taken easily as such via oral route or by dispersing in water. It is more chemically stable than liquid dosage form. It is convenient for the physician to prescribe a specific amount of powder. The Onset of action is faster as compared to tablet and capsules, because it can easily dissolved in body fluids due to very small particle size it get dissolve rapidly. Easy to carry. No liquid solvents or very less solvents are required during formulations. Easy administration to the patient by dissolving in suitable liquids. Powders are more economical than other dosage form since they do not require any special machinery or techniques.

4. Drugs have bitter taste, nausea and unpleasant odour cannot be administered in powder form. The Deliquescent and hygroscopic drugs cannot be dispensed in the powdered form so they should be packed in double wrapping. Drugs which get affected by atmospheric condition are not suitable for dispense. Quantity less than 100 mg cannot be weighed conveniently. The dispensing of powder is time consuming . Disadvantages

5. Classification The pharmaceutical powders are classified as follows, Bulk powders for Internal use. Bulk powders for External use. Simple powder for internal use. compound powder for internal use. Powders enclosed in cachets and capsules. Compressed powders (tablets).

6. 1. Bulk powders for internal use When the accuracy of dosage form is not required at the time of administration , they are dispense in the bulk form. Bulk powders consists of several doses of powders. They are supplied in wide mouth container with a spoon to permit easy dispensing for patients. The non potent substances which are administered in bulk form are antacids and laxatives . Eg’s, Compound Rhubarb powders (Gregory’s powder). Rhubarb powder. Light magnesium carbonate. Heavy magnesium carbonate. Ginger powder.

7. 2. Bulk powders for external use Bulk powders for external use are non potent substances . These powders are supplied in the cardboards, glass or plastics containers which are often designed for the specific method of application. They are generally supplied in perforated or sifter top containers. The label on the containers must indicate ‘ powders for external use ’. The bulk powders which are commonly used for external applications are as follows, Dusting powders Insufflations Snuffs Dentifrices

8. Dusting Powders These are meant for external application to the skin. It is applied in very fine state to avoid local irritation . These powders are passed through sieve no. 85( 180µm) to get a fine powder. There are two types of dusting powders, Medical dusting powder Surgical dusting powder Medical dusting powders are mainly used for superficial skin condition. Surgical dusting powders are used in body cavities or wound or umbilical cords of infants . It must be sterilized before use. Dusting powders are generally prepared by mixing two or more ingredients and they contains antiseptic, astringent, antiperspirant, anti pruritic . These may also applied with powder puff or sterilized gauze pad.

9. Insufflations Insufflations are medicated dusting powder meant for introduction into body cavities like nose, throat, ears and vagina for treating infections with the help of an instruments called as insufflators. It sprays the powder into a stream of finely powder. It is available in pressurized aerosols which can be used for potent drugs. Insufflations are used to produce local and systemic effect from the drugs that get destroyed in the gut .

10. Snuffs are finely divided solid dosage forms of medicament which are inhaled into nostrils. It contains antiseptics, bronchodilators, decongestants for there local and systemic effects. Snuffs are dispensed in flat metal boxes or glass container containing lid with extension. Snuff

11. Dentifrices Dentifrices are the dental powders are applied with the help of a tooth brush for cleaning the surface of the teeth. Dental powders contain detergents or soap, abrasives, antiseptics and coloring and flavoring agents incorporated in a suitable base. Base is calcium carbonate. The detergent is in the form of soap and the abrasive action is provided by finely powdered pumice stone. Essential oils are added to provide flavor and freshness to the mouth as well as antiseptic action. Eg, Rx Hard soap, in fine powder - 50.0 g Precipitated calcium carbonate - 935.0 g Saccharin sodium - 2.0 g Peppermint oil - 4.0 ml Cinnamon oil - 2.0 ml Methyl salicylate - 8.0 ml

12. In this form of powder, each individual dose is enclosed in the paper wrap. If the number of ingredient is one, the powder is said to be simple and if it is consists of more than one powders it is said to be compound powders . The minimum quantity of each powder shouldn’t be less than 100 mg. Simple powders contains only one ingredients either in crystalline or amorphous form . When the powder is in crystal form then it is reduced into fine powder by using size reduction methods . For dispensing of powders, w eigh the powder and divide into number of doses and wrapped as an individual dose. Eg, Aspirin – 300 mg Procedure – powder the aspirin, weigh the required quantity of aspirin and wrap each powder in individual powder paper. 3. Simple powders

13. Compound powders contain two or more than two substance which are mixed together and then divided into desired number of individual dosed and dispensed into each powder paper. Eg, Aspirin 300 mg Paracetamol 150 mg Caffeine 50 mg Procedure – Weigh accurately each powder and mix them as per ascending order of their weight. Weigh 500 mg of the mixed powder for each powder and wrap each dose individual in powder papers. 4. Compound powders

14. 5. POWDERS IN CACHETS Cachets are the solid unit dosage form of drugs and are called as wafer capsules . These are molded from rice paper which is made by pouring a mixture of rice flour and water between two hot polished cylinders then the water evaporates and a sheet of wafer is formed. Cachets are used to enclose nauseous or disagreeable powders which are available from 0.2 to 1.5 g of powder in it. They are quite hard to swallow as such but they are softened by dipping in water for few seconds and then place on the tongue and swallowed with a water. Advantages – 1. Easy to prepare. 2. Disintegrate quickly in stomach. 3. Drugs can be easily dispensed. 4. Large dose of drug can be swallow by using cachets.

15. Wet seal cachets – it is made of two similar convex halves having flat edges. The weighed quantity of drug is placed in one half and edges of other half is moistened with water and placed over first half containing drug. The flat edges of both halves are pressed together to seal it. Dry seal cachets - it consists of two halves, the upper half and the lower half. The diameter of the upper half is slightly larger than the lower half. The powdered drug is filled in lower half and upper half is fitted over it. The filled cachets are then sealed in machine by pressing the two halves. Types of Cachets

16. 6. TABLET TRITURATE These are powders molded into tablets. Molded tablets are flat circular disc are usually contains potent drugs which is mixed with lactose, dextrose or any other diluents.

17. Preparation of powders The powder is prepared in following steps, Reduction of particle size of all ingredients Sieving Weighing of each ingredient Mixing Packaging

18. Reduction of particle size of all ingredients The reduction in particle size is done following methods, Grinding – firstly all the particles are individually get grinded by grinder or mortar and pestle to reduce their size from coarse to fine. Sifting – firstly the whole powder is allowed to get sifted from fine sieve. Then the coarse powders retained over the sieve is again triturated and repeated the sieving procedure to get fine particles. 2. Sieving Sieving is done to separate the particles of different sizes from each other to avoid the irregular contents of powder dosage form. There are different no. of sieves available varying from finest to coarse. Egs, Sieve No. – 100, 80, 60, 40, 20 etc.

19. 3. Weighing of each ingredient First of all, the material to be used in the formulation are selected. If any hygroscopic material is present in the formulation it is then allowed to dry completely. After each of the content of powder formulation taken separately and put on the left side of weighing balance. The required quantity is then take from main container to butter paper and weighed the required quantity. Put the weighed material on the right side of weighing balance.

20. The aim of mixing is to obtain a homogeneous association of several solid products. Factors influencing the mixing of powders are nature of surface, density, particle size, particle shape and proportion of materials. If these factors are not under control, segregation can occur and the t ypes of segregation includes percolation and densification. Methods of Powder Mixing 1. Mechanical Mixing 2. Hand Mixing - a. Spatulation (Spatula + Tile) b. Trituration (Mortar + Pestle) c. Tumbling (Wide mouth closed container) 3. Geometric dilution - Entire quantity of potent drug + n volumes of the diluents + (2n volume) of the diluents + (4n volume) of the diluents repeated until all the diluents are used. 4. MIXING OF POWDERS

21. 5. Powder packaging The paper wrapping is divided powders are supplied or dispensed by wrapping in suitable paper (glazed). The paper used for packing of should have following properties , It should fold easily. It should protect the powders without cracking at the fold. It should impermeable to atmospheric condition. It should be water repellant. It should be light weight and elegant. Powder papers of special grades are available readily in different in size otherwise pharmacist may cut the sheets in suitable size. The shape of the paper should be rectangular and wrapping of powders may be single or double wrapping. If p acked in container, the sifter top containers, pressurized containers, flat metal boxes.

22. Effervescent granules Granules have particle size larger than the powder. Basically granules are the wet clumps of the powder which are prepared after moistening the powder. This contains sodium bicarbonate and either citric acid, tartaric acid or sodium biphosphate in addition to the active ingredients. On making solution in water, carbon dioxide is released as a result of the acid base reaction. The effervescence from the release of the carbon dioxide serves to mask the taste of salty or bitter medications. The completed product must be dispensed in tightly closed glass containers to protect it against the humidity of the air.

23. Effervescent powders The preparative techniques have been reported for effervescent powders such as a fluidized bed procedure in which the powders are blended and then suspended in a stream of air in a Wurster chamber. Water is sprayed into the chamber resulting in a slight reaction and an expansion of the particles to form granules ranging in size from 10 to 30 mesh. This approach apparently offers a number of advantages over the older techniques. The extent of reaction and particle size are controlled during the manufacture. A drying oven , trays and even grinding devices are not required . Furthermore, the technique lends itself to a continuous as well as a batch operation.

24. Special Problems Volatile Substances - The loss by volatilization may be prevented or retarded by use of heat-sealed plastic bags or by double wrapping with a waxed or glassine paper inside of a bond paper. Eutectic Mixtures Liquids result from the combination of phenol, camphor, menthol, thymol, antipyrine, phenacetin, acetanilid, aspirin, salol and related compounds at ordinary temperatures. These so called eutectic mixtures may be incorporated into powders by addition of an inert diluent. Magnesium carbonate or light magnesium oxide are used commonly and effective diluents for this purpose, although kaolin, starch, bentonite and other absorbents have been recommended.

25. 3. Presence of Liquids - In small amounts, liquids may be incorporated into divided powders. Magnesium carbonate, starch or lactose may be added to Increase the absorbability of the powders if necessary. When the liquid is a solvent for a nonvolatile heat-stable compound, it may be evaporated gently on a water bath. Lactose may be added during the course of the evaporation to increase the rate of solvent loss by increasing the surface area. 4. Deliquescent Substances - Substances that become moist because of affinity for moisture in the air may be prepared as divided powders by adding inert diluents. Double wrapping is desirable for further protection. Extremely deliquescent compounds cannot be prepared satisfactorily as powders. 5. Hygroscopic Powders – substances that take or absorbs the moisture from the environment are called as Hygroscopic substances. The powders which are hygroscopic in nature are if placed open in room temperature they are more prone to collect the moisture present in the surroundings.

26. Thank You