powder and granules for pharmacy students

powder and granules

1. Powders & Granules

2. CONTENTS Powder s and Granules Introduction Advantages and disadvantages General Method of preparation Classification Method of preparation of different powders Granules Effervescent granules

3. Introduction: A Pharmaceutical powder is a mixture of finely divided drugs or chemicals in a dry form meant for internal or external use. They may be Crystalline or Amorphous form. The Particle size of a Powder plays an important role and affects dissolution, absorption and therapeutic effectiveness of drugs.

4. Advantages of powders : Can be used both internally and externally. More stable than other dosage forms flexibility of compounding and prescribing a specific quantity. Less chances of incompatibility. Rapid onset of action Easy to carry. Large quantity also can be administered conveniently. More economical because no special equipment is required for preparation.

5. Disadvantages of powders : Bitter, nauseous and unpleasant taste drugs can not be prepared in the powder form. Deliquescent and Hygroscopic drugs can not be dispensed in the powder form. Drugs which get affected by atmosphere are not suitable. Dispensing is time consuming. Less quantity can not be weighed conveniently on dispensing balance.

6. General method of preparation of Pharmaceutical powders It involves two steps: The process of reducing the particle size ( Comminution ) The process of Blending

7. COMMINUTION OF DRUGS On a small scale, the pharmacist reduces the size of chemical substances by grinding with a mortar and pestle. A finer grinding action is accomplished by using a mortar with a rough surface (as a porcelain mortar) than one with a smooth surface (as a glass mortar). Grinding a drug in a mortar to reduce its particle size is termed trituration or comminution .

8. When two or more powdered substances are to be combined to form a uniform mixture, it is best to reduce the particle size of each powder individually before weighing and blending. Depending on the nature of the ingredients, the amount of powder, and the equipment, powders may be blended by spatulation, trituration, sifting, and tumbling. BLENDING POWDERS

9. Spatulation Spatulation is blending small amounts of powders by movement of a spatula through them on a sheet of paper or an ointment tile. It is not suitable for large quantities of powders or for powders containing potent substances, because homogeneous blending is not as certain as other methods.

10. Trituration Trituration may be employed both to comminute and to mix powders. If simple admixture is desired without the special need for comminution, the glass mortar is usually preferred.

11. What is geometrical dilution ??? When a small amount of a potent substance is to be mixed with a large amount of diluent, the geometric dilution method is used to ensure the uniform distribution of the potent drug. By this method, the potent drug is placed with an approximately equal volume of the diluent in a mortar and is mixed thoroughly by trituration. Then, a second portion of diluent equal in volume to the mixture is added and the trituration repeated . This process is continued by adding an equal volume of diluent to the powder mixture and repeating this until all of the diluent is incorporated.

12. Sifting Powders may also be mixed by passing them through sifters like those used in the kitchen to sift flour. Sifting results in a light, fluffy product. This process is not acceptable for the incorporation of potent drugs into a diluent powder.

13. Tumbling : Another method of mixing powders is tumbling the powder in a rotating chamber. Special small-scale and large-scale motorized powder blenders mix powders by tumbling them . Mixing by this process is thorough but time consuming . Such blenders are widely employed in industry, as mixers that use motorized blades to blend powders in a large vessel.

14. Classification of Powders Bulk Powders for internal use Bulk Powders for External use Simple and compound Powders for internal use Powders enclosed in cachets and capsules. Compressed powders (Tablets)

15. 1.Bulk powder for internal use They are mixture of finely divided drugs and / or chemicals in a dry form that may be intended for internal use (oral powders ) Powders are dispensed in bulk when the dose accuracy is not important. Contain several doses and supplied in wide mouthed containers. Non potent substances like Antacids Laxatives

16. 2. Bulk powder for external use They are mixtures of finely divided non potent drugs and/ or chemicals in a dry form that may be intended for external use available in multiple doses (dusting powder) Types: a)Dusting powders b)Insufflations c) Snuffs d )Dentifrices

17. D usting powder s These are meant for external application on to the skin and are applied in a very fine state of sub division to avoid local irritation. Medical – for superficial skin infections Surgical – Body cavities and on wounds. The major ingredients include: Talc, starch and Kaolin Antiseptic, Astringent, Absorbent, Antiperspirant and Antipruritics . Dispensed in sifter top container or aerosol container

18. Insufflations These are medicated dusting powders meant for introduction into the body cavities such as nose, throat, ears and vagina with the help of a apparatus known as Insufflator . It sprays the powder into a stream of finely divided particles all over the site of application. Insufflations are used to provide local effect, as in the treatment of ear, nose and throat infection with antibiotics or to produce systemic effect of drugs.

19. Snuffs Finely divided solid dosage forms of medicament which are inhaled into nostrils for its Antiseptic, Bronchodilator and Decongestion actions.

20. Dentrifrices (Tooth powders) Powders which are applied with the help of a brush for cleaning the surface of the teeth. They contain a suitable detergent or soap, Abrasive and flavor. Abrasives – Calcium sulphate , Magnesium carbonate, Sodium carbonate and Sodium chloride. Rx, Hard soap – 50 g Calcium carbonate – 935 g Saccharin sodium – 2 g Peppermint oil – 4 ml

21. Simple and Compound powders for internal use Each individual dose is enclosed in paper. Simple powder - one ingredient Compound powder – more than one The minimum quantity of powder should be NLT 100 mg Simple powder – A simple powder contains only one ingredient either in crystalline or Amorphous form. Rx, Aspirin – 300 mg Make powder and send 6 doses.

22. Compound powder – A compound powder contains two or more ingredients which are mixed together and then divided into desired number of individual doses which are dispensed into each powder paper. Rx, Aspirin – 300 mg Paracetamol – 150 mg Caffeine – 50 mg Make powder and send 8 doses.

23. Powders enclosed in cachets Cachets are the solid unit dosage forms of the drug which are moulded from rice paper. These are made by pouring a mixture of rice flour and water between two hot, polished, revolving cylinders. Cachets are used to enclose nauseous or disagreeable powders and are available in different sizes from 0.2 to 1.5 gm of powder. Softened by dipping in water for a few seconds and then placed on the tongue and swallowed with a draught of water.

24. Types of cachets Wet seal cachets: Made up of 2 similar convex halves having flat edges. The powder is placed in one half, second half is placed on it and the edges are moistened with water and pressed to seal. Dry seal cachets: Two halves, upper and lower, where the diameter of the upper half is slightly larger than lower half. The powder is filled in lower half, and the upper half is placed on it and pressed for sealing using machines.

25. 5. Tablet triturates Powders molded into tablets. Flat, circular disc shaped usually contains a potent substance which is mixed with lactose, dextrose or other diluents. The moulds consists of Upper perforated plate Lower plates having pegs The mould are generally available in several sizes ranging from 30 to 250 mg.

26. The solid medicament along with diluent are powdered and converted into a stiff paste using 60 % alcohol. The paste is pressed on to the upper perforated plate using spatula and placed on to the lower plate. A little pressure is applied over the top plate to move downward, leaving the mould tablets on the projected pegs which makes to eject the tablets. Tablets are kept in hot air oven for drying. Preparation of Tablet triturates

27. Powders involving special problems Volatile substances Hygroscopic and Deliquescent powders Efflorescent powders Eutectic powders Liquids Explosive powders Potent drugs

28. Volatile substances Vegetable drugs contain volatile oils. To prevent the loss the vegetable drugs must be powdered lightly. Volatilization of menthol, camphor and essential oils may happen on incorporation. Solution: This is prevented or minimized by double wrapping. The inner wrapper may be of a wax paper and the outer wrapper may be a thick paper.

29. Hygroscopic and deliquescent substances Hygroscopic – absorbs moisture Deliquescent – absorbs moisture and becomes liquid. Ammonium chloride, Phenobarbitone , sodium bromide, sodium iodide, pot citrate, zinc chloride. Solution: Prepare in Granular form. Should not be finely powdered Double wrapping Humid weather - Further wrapping in plastic paper or aluminium foil.

30. Efflorescent powders Some crystalline substances liberate water of crystallization on exposure to humid atmosphere or during trituration and becomes wet or liquefy. Caffeine, Citric acid, Ferrous sulphate . Solution: Using corresponding anhydrous salt. Use of inert substance by mixing before incorporating with other ingredients.

31. Eutectic powders When two or more substances are mixed together they liquefy due to the formation of a new compound which has a lower melting point than RT. Menthol, Thymol , Camphor, Aspirin, Phenacetin . Solution: Two methods Dispense as separate set of powders with directions that one set shall be taken as a dose. Use of inert Absorbent like magnesium carbonate and to be mixed gently.

32. Liquids Some times liquid medicaments are to be incorporated in powders. Small quantity – mixed with powder ingredient in the formula. Large quantity – Absorbent Liquid extracts and tinctures – evaporated to concentrated mass, absorbent is added and again subjected to evaporation.

33. Explosive powders When an oxidizing substance like Potassium chlorate is mixed with reducing substance, such as Tannic acid , there are chances of violent explosion. Solution: As far a possible such prescription should not be dispensed. Powder each ingredient separately in a mortar and mix them lightly. Powder each ingredient separately and dispense them in separate powder paper with suitable direction.

34. Potent drugs The substances having a maximum dose of less than 60 mg and poisonous substances. Small quantities of potent drugs should not be weighed on dispensing balance. Solution: Geometric dilution method Diluent like Lactose is added to potent drug to make a weighable quantity. Drug is triturated and mixed with equal quantity of diluent followed by trituration . Remaining quantity is incorporated in successive portions with thorough trituration .

35. G ranules Granules are aggregations of fine particles of powders in a mass of about spherical shape . Prepared for the solids which are to be administered orally in large quantities. They cannot be prepared as tablets or capsules because of large dose. Difficult to dispense as such in powder form because of bitter and nauseous taste. Difficult to convert into liquid because of stability problem. The only alternative is to prepare granules.

36. Method of preparation of granules Drug is mixed with sweetening agent, coloring agent and a suitable granulating agent mixed with suitable solvent is added to get a damp mass. Pass through Sieve # 10 to make granules. Drying at 60⁰c in Hot air oven and the dried granules are passed through sieve # 20 and stored in a dry well closed wide mouthed container. Now a days antibiotics in granules form for reconstitution.

37. EFFERVESCENT GRANULES Effervescent granules are coarse to very coarse powder containing a medicinal agent in a dry mixture usually composed of sodium bicarbonate, citric acid and tartaric acid When added to water the acid and base react to liberate carbon dioxide resulting in effervescence. The resulting carbonated solution mask the undesirable taste of medicinal agent. Ef fervescent tablets and granules are intended to be dissolve d in water before use .

38. PREPARATION Effervescent granules are prepared by two general methods. The dry or fusion method The wet method The source of binding agent is not water of crystallization from the citric acid but the water added to the mass of powder as moistening agent . In this method all of powder may be anhydrous as long as water is added to the moistening agent . Just enough liquid is added to prepare a mass of proper consistency then the granules are prepared and dried. WET METHOD

39. Heat or fusion method In fusion method the one molecule of water present in each molecule of citric acid acts as the binding agent for the powder mixture. Before mixing the powder the citric acid crystals are powdered and then mixed with other powders of the same size to ensure uniformity of the mixture. After mixing te powder is placed in an oven at 34- 40 ⁰ c . 3NaHCO 3 + C 6 H 8 O7.H 2 O → 4 H 2 O + 3 CO 2 + Na 3 C 6 H 5 O 7

40. Heating cause s t h e release of water of crystallization from t h e citric acid causing softening of powder , when it reached the proper consistency it is removed from the oven and rubbed through a sieve produced large granules. Sieve 4 produce large granules , sieve 8 produce medium size granules and sieve 10 produce small granules D ry at 54 ⁰ c and transferred into Air tight container.