Definition Powders are intimate mixtures of dry, finely divided drugs and/or chemicals that may be intended for internal or external use.
1.
2. 3.
4.
Flexibility of compounding-easy to prepare Good chemical stability Rapid dissolution due to small particle size Fast action and better bioavailability
1. 2. 3.
Time consuming Inaccuracy in dose Unsuitable for many unpleasant tasting, volatile, oxidizing, hygroscopic and deliquescent drugs.
Based on Usage -powders for external use. -powders for internal use. Based on quantity -bulk powders -divided powders
Agglomerates of powders Used as such as dosage form or used to prepare tablets e.g. effervescent granules- to mask unpleasant taste of drugs.
Comminution of Drugs (Particle Size reduction of drugs) Blending of Powders
Trituration -Grinding with mortar and pestle.
Mills and pulverizers e.g. FitzMill Levigation - a paste is i s formed by combining combining the powder powd er and a small amount of liquid (levigating agent) in which the powder is insoluble. The paste is then triturated to reduce particle size. The levigated l evigated paste may be mixed with base well with help of a spatula and tile. Mineral oil and glycerin are generally used levigating agent. Pulverization by intervention- size reduction using a solvent and which is removed after size reduction. Suitable for resins and gummy substance. E.g. camphor.
a. Spatulation -Mixing is done using spatula and tile or sheet -useful for solid substances that liquefy or form eutectic mixtures (i.e., mixtures that melt at a lower temperature than any of their ingredients; when in close, prolonged contact with one another) -not suitable for potent drug -lack of homogenous mixing
b. Trituration It is used both to comminute and to mix powders. If comminution is desired, a porcelain or ceramic mortar with a rough inner surface is preferred to a glass mortar with a smooth working working surface. A glass mortar is preferable preferable for chemicals chemicals that stain a porcelain or ceramic surface as well as for simple admixture of substances without special need for comminution. A glass mortar cleans more readily after use.
c. Geometric dilution It is used when potent substances must be mixed with a large amount of diluent. The potent drug and an approximately equal volume of diluent are placed in a mortar and thoroughly mixed by trituration. A second sec ond portion ion of diluent, dilu ent, equal vvolume olume e to the secon second d port portio portion n of dilue nt, equa equall in volum vo lume the powder mixture in the mortar, is added, and trituration is repeated. The process is continued; equal volumes of diluent are added to the powder mixture in the mortar until all of the diluent is incorporated.
d. Sifting. Powders are mixed by passing them through sifters similar to those used to sift flour. This process results in a light, fluffy product. Usually, it is not acceptable for incorporating potent drugs into a diluents base. e. Tumbling is the process of mixing powders in a large container rotated by a motorized process. These blenders are widely used in industry, as are large-volume powder mixers that use motorized blades to blend the powder in a large mixing vessel.
Depending on their intended use, powders are packaged and dispensed as 1. bulk powders or 2. divided powders.
They are dispensed in bulk containers. A perforated, or sifter, can is used for external dusting, and an aerosol container container is used for f or spraying spraying onto skin. A A wide-mouthed wide-mouthed wide-mouthed glass jar permits easy removal of a spoonful of powder. E.g. of bulk powders are as follows (a) Antacid and laxative powders (b) Douche powders (c) Medicated and non medicated powders for external use (d) Dentifrices or dental cleansing powders powders are used for oral hygiene. (e) Powders for the ear, nose, throat, tooth sockets, or vagina are administered with an insufflator, or pow powder der powd er blower.
These are dispensed in individual doses, usually in folded papers. They may also be dispensed in metal foil, small heat-sealed or resealable plastic bags, or other containers. After the ingre iingredien ngredien dients ts are are weighe we d,, comm ccommi omminute inuted, d,, and aan nd weighed weiighed, ghed, co mminuted nuted, d mixed, the powders must be accurately divided into the prescribed number of doses. Depending on the potency of the drug substance, the pharmacist decides whether to weigh each portion separately before packaging or to approximate portions by the block-and-divide method.
Four basic types are used: (a) Vegetable parchment is a thin, semi opaque, moisture-resistant paper. (b) White bond is an opaque paper that has no moisture-resistant prope properties. rties. (c) Glassine is a glazed, transparent, moistureresistant paper. (d) Waxed paper is a transparent waterproof paper. Hygroscopic and volatile drugs are best protected with waxed paper that is double wrapped and covered with a bond paper to improve the appearance. Parchment and glassine papers are of limited use for these drugs.
Powders with volatile substances, eutectic mixtures, liquids, and hygroscopi hygroscopicc or deliquescent substances present problems
e.g., camphor, menthol, essential oils) can be lost by volatilization after they are incorporated incorporated into powders. It is prevented by using heat-sealed plastic bags b ags or double wrapping with waxed or glassine paper inside white bond paper.
Liquids are incorporated into divided powders in small amounts. (1) Magnesium carbonate, starch, or lactose can be added to increase the absorbability of the powders by increasing the surface area. (2) When the liquid is a solvent for a nonvolatile heat-stable compound, it is evaporated gently in a water bath. Some fluid extracts and tinctures are treated in this way.
Hygroscopic and deliquescent substances that become moist because because of an affinity for f or moisture in the air. Substance which absorb moisture are called hygroscopic If high qty of water is absorbed absorbed to make the material material liquid then it is called as deliquescen deliquescent. t. deliquescent. E.g. Potassium citrate, ammonium chloride, citric acid, tartaric acid, sodium iodide. iodide. It can be prepared as divided powders by adding inert diluents/ absorbe absorbents. nts. absorben ts. Double wrapping wrapping is desirable protection. n. desirable for further protectio Prepared as granules to minimize the exposure to moisture.
Some of the drugs when mixed together tend to liquefy due to formation of new compound (due to decrease in melting point). e.g. menthol, thymol, phenol, aspirin, camphor and menthol One of the ingredient added in a powder may reduce the melting point of other ingredient and forms a liquid. Methods to Overcome: 1. Can be minimized by using inert diluents /absorbent like magnesium carbonate, carbonat e, kaolin, starch, carbonate, starch, lactose, light magnesium oxide. 2. They can be dispensed in separate sets of powders and labelled with suitable direction
Crystalline substance liberates water of crystallization due to change in humidity are called efflorescent substances. e.g. caffeine, cocaine, codeine phosphate, Sodium carbonate, sodium phosphate. Methods to overcome: Use anhydrous salt
When some oxidizing and reducing substances are mixed in mortar, there are chances of explosion. Very rare combinations. combi nations. e.g. Potassium chlorate and tannic acid. Method to overcome: separately powder and dispense.
Hygroscopic, Hygroscopic, deliquescent, deliquescent, or volatile powders- packed in glass jars rather than pasteboard containers. Amber or green green glass for light-sensitiv lig ht-sensitive e light-sensiti ve components. Should be stored in tightly closed containers. Products for external use must indicate “For External Use Only” on the label
Has some advantage over powder Free flowing More stable Better dose measurements Used in the manufacture of tablets and capsules
Effervescent salts are granules or coarse to very Effervescent coarse powders containing a medicinal agent. It is a dry mixture composed of sodium bicarbonate, citric acid, and tartaric acid. When added to water, the acids and base react to liberate carbon dioxide, resulting in effervescence effervescence.. The resulting carbonated solution masks undesirable taste of any medicinal agent. Using granules or coarse particles of the mixed powders rather than small powder particles decreases the rate of solution s olution and prevents violent and uncontrollable uncontrollab le effervescence effervescence..
Prepared by two general methods: (a) the dry or fusion method : Ingredients are mixed and heated to release water of crystallization crystallization from citric acid. Release of water will produce CO2. The mixture will become spongy while heating at 40 0 C. Then the spongy mass passed through sieve to produce granules. (b) the wet method- water/alcohol used to prepare wet mass which is passed through sieve to produce granules
