3 Advantages of powders: Good chemical stability compared with fluidsuseful for bulky drugs with large dose, e.g. indigestion powder.Easy to swallow even in large bulk, especially if mixed with drink food (useful for stomach- tube feeding)The smaller particle size of powders causes more rapid dissolution in body fluids, increases drug bioavailability, and decreases gastric irritation compared with tablets
4 Disadvantages of Powders Not suitable for drugs unstable in atmospheric conditionsNot suitable for bitter, nauseating, deliquesnt and corrosive drugs.Inaccuracy of dose in case of bulk powderInconvenient to carry.
6 Oral divided powder may contain one or more active ingredients together with an inert diluent to produce a minimum quantity of 120 mg.Oral undivided powder are usually a simple mixture of the prescribed medication without additional ingredients.
7 Preparation of powders 1- Reduction of particle size of all ingredients to the same range to prevent stratification.2- Sieving.3- Weighing of each ingredient.4- Mixing.5- Packaging.
8 Example of undivided oral powder: prepare 100 gram Compound magnesium Trisilicate Oral Powder BP 1988.ingredients amountmagnesium trisilicate 250 gchalk, in powder gsodium bicarbonate gheavy magnesium carbonate 250 gAction and Use: Adsorbent and antacid for treatment of dyspepsia.
9 Example of divided oral powder: Prepare Oral Rehydrated Salts BP 1988Ingredient amount to prepare 1 litre solutionSodium chloride gPotassium chloride 1.5 gSodium bicarbonate 1.5 gAnhydrous glucose gAction and use: Rehydration and electrolyte replacement in treatment of diarrhea.
10 Methods of Powder Mixing 1- Mechanical Mixing2- Hand Mixing:2.1- Spatulation (spatula + tile)2.2- Trituration (mortar + pestle)2.3- Tumbling (wide mouth closed container)Geometric dilution:Entire quantity of potent drug (x volume) + (x volume) of the diluents + (2x volume) of the diluents + (4x volume) of the diluents………repeated until all the diluents are used.
11 Problems encountered in powder formulation 1- Hygroscopic and Deliquescent PowderProblem: Absorption of moisture from air leading to partial or complete liquefaction.Solution: A- Applied in a granular form to decrease the exposed surface to air.B- Packed in aluminum foil or in plastic film packetsC- Addition of light magnesium oxide to reduce the tendency to dampD- Addition of adsorbent materials such as starchExamples: - halide salts (ex. Sod. Iodide)- Certain alkaloids (physostigmine Hcl)
12 Problems encountered in powder formulation 2- Efflorescent powdersProblem: Crystalline substances which during storage loose their water of crystallization and change to powder (to be efflorescent). The liberated water convert the powder to a paste or to a liquid.Examples: Alum- atropine sulfate- citric acid- codeine phosphate…Solution: Using the anhydrous form, and treating it in a manner similar to hygroscopic powders
13 Problems encountered in powder formulation 3- Eutectic MixturesProblem: mixture of substances that liquefy when mixed, rubbed or triturated together. The melting points of many eutectic mixtures are below room temperature.Examples: menthol- thymol- phenol- salol- camphor…….Solution: A- using inert adsorbent such as starch, talc, lactose to prevent dampness of the powderB- dispensing the components of the eutectic mixture separately.
14 Problems encountered in powder formulation 4- Incorporation of LiquidsSolution:A- The liquid is triturated with an equal weight of the powder and the remaining powder is added in several portions with trituration.B- Adsorbent is incorporated, usually light kaolin.
15 Problems encountered in powder formulation 5- Incorporation of ExtractsProblem: Some plant extracts are available as powders or as semisolid (e.g., liquid extract of liquorice) .Solution:A- The powdered extracts have no problems and treated generally as powdersB- Semisolid extract should be mixed with an equal quantity of lactose and reduced to a dry powder by evaporation before incorporation with other ingredientsC- Careful heating, if present, to save potency of the extract.
16 Problems encountered in powder formulation 6- Potent DrugProblem: Limited precision and accuracy of the used balances to weight small amounts of potent drugs.Solution: Drug triturates:A- Suitable diluents like lactose are mixed with the potent drug to form %w/w drug triturates.B- Very fine powders should be used in the trituratesC- Geometric dilution to prepare drug triturates
17 Example:Send 3 powders each containing 8 mg propranolol hydrochloride for a child weighing 8 kgone powder four powdersPropranolol hydrochloride 8 mg 32 mgLactose mg 448 mgTotal mg 480 mgTrituration:propranolol hydrochloride 100 mglactoseSo, each 100 mg of triturate contains 20 mg drug and therefore 160 mg of triturate will contain 32 mg
18 Problems encountered in powder formulation 7- Incompatible saltsProblem: Chemically incompatible salts when triturated together produce discoloration, chemical deterioration or loss of potency.Solution:A- Compounding such substances with minimum pressureB- Use a convenient method for mixing the powder like tumbling in a jar or spatulation on a sheet of paper.C- Each substance should be powdered separately in a clean mortar and then combined with other ingredients gently.D- Powder and dispense separately.
19 Problems encountered in powder formulation 8- Explosive mixturesProblem: Oxidizing agents(ex. Pot. Salts of chlorate, dichromate, permanganate and nitrate- Sod. Peroxide- silver nitrate and silver oxide) explore violently when triturated in a mortar with a reducing agent ( ex. sulfides- sulfur- tannic acid- charcoal).Solution:A- Comminute each salt separately.B- Subject to a minimum pressure.
20 Special Powders 1- Effervescent Powders Definition: Mixture of organic acid and alkali effervesces when subjected to water due to reaction between the acid and the base with evolution of co2Examples: Citric or tartaric acids with sodium carbonate or bicarbonateUses: The liberated carbon dioxide has the following advantages:It masks the bitter and nauseous taste.It promotes gastric secretions.It acts as a carminative.psychological impression at the patient..
21 Special Powders 1- Effervescent Powders Formulation:- Bulk powders or divided powders- Packed in separate packages of contrasting colors.- The contents are mixed in a quantity of water at the time of dosing.- The liquid is consumed just after the reaction begin to subside.
22 Special Powders 2- Effervescent Granules Definition: Sweetened effervescent powders formulated as granules.Granulation:1- Wet method: By the addition of a binding liquid (Alcohol is frequently used).2- Dry method: Heating effloresced powder to liberate the water of crystallization which then acts as the binding agent
23 Special Powders 2- Effervescent Granules Wet GranulationProcedure:1- The powders are mixed without pressure in a suitable container.2- Alcohol is added in portions with stirring until a dough like mass is formed.3- The materials are then passed through sieve # 6.4- The resulted granules are dried at a temperature not exceeding 50ºC.5- The granules are packed in air tight containers
24 Special Powders 2- Effervescent Granules Dry granulation Procedure:1- All ingredients, except citric acid monohydrate, are dried and passed through sieve # 60.2- The powders are thoroughly mixed and citric acid crystals are added at last (un-effloresced citric acid contains one molecule of water of crystallization).3- The mixture is spread in a shallow dish and placed in an oven previously heated ( ºC). Upon heating citric acid crystals, the water of crystallization effloresces and citric acid transforms to the powder form.
25 Special Powders 2- Effervescent Granules Dry granulation Follow, Procedure:4- The use of a water bath surrounding the beaker (or any container) in which the powders are stirred is a more convenient method to prevent local over heating.5- No stirring until the powders become moist and form doughy mass.6- The mass is then granulated by passage through sieve # 6 and dried.
26 Special Powders 2- Effervescent Granules Packaging:* Effervescent granules or powders suffer from the short shelf life, especially if they are filled into wide-mouthed screw capped containers.* Recently, the stability of effervescent granules and powders is greatly improved by their packing in aluminum bags tightly closed.
27 Special Powders 3- Dusting Powders It is a very fine, light powder for external used as an insecticide, medicine, toiletry, etc.Requirements:1- Homogenous and very fine2- Free from irritation.3- Flow easily.4- Have good covering capacity.5- Have good adsorptive and absorptive capacity.6- Spread uniformly over body surface.7- Cling (adhere) to skin surface after application.8- Protect the skin from irritation caused by friction, moisture and chemical irritants.
28 Special Powders 3- Dusting Powders Application:1- Medicated dusting powders may be applied either to intact skin or to open wound and mucous membranes.2- powders applied to open wound must be sterilized3- Particle size should be very small. It is better to be micronized or those passes through # 100 sieve.4- Highly sorptive powders should not be used on areas exude large quantities of fluids to avoid hard crust formation.Function:Lubricants- protective- adsorbents- antiseptic - astringents- antiperspirants
29 Special Powders 3- Dusting Powders Packaging:Dispensed in sifter- top cans or pressurized packs (aerosols).Aerosols protect the powder from air, moisture and contamination and more convenient for application.
30 Example of dusting powder: Ingredientzinc oxide gstarch, in powder 250 gpurified talc, sterilized 250 gAdvice to patient: the powder should be dusting lightly onto the affected areaAction and use: absorbent dusting powder, mild antiseptic
31 Special Powders 4- Insufflations Definition: Finely divided powders to be blown into body cavities such as ears, nose, throat and vagina.- Drug and other ingredients are packed into hard gelatin capsule. After insertion into the insufflator the shell is broken and the flow release of powder is controlled by the patient’s own respiratory effort.Packaging:Insufflators (powder– blower) : difficult to obtain a uniform dose.