Powder
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NTRODUCTION:-: INTRODUCTION: Defination:- A pharmaceutical powder is a mixture of finely divided drug &/or chemicals in dry form. ADVANTAGES:internal &external use. More stable than liquid. Convenient for the physician. Chances of less incompability . Onset of action is rapid . Easy to carry. Large quantity can be administered. Convenient for small child & elderly patient. More economical. DISADVANTAGES:Can’t dispense Bitter , nauseous & unpleasant taste drug. Can’t dispense hygroscopic & deliquescent drugs. Dispensing is time consuming process. Quantity less than 100mg can’t weighed on dispensing balance. Can’t dispense volatile drugs. METHOD FOR WRAPPING DIVIDED POWDERS: METHOD FOR WRAPPING DIVIDED POWDERS Refer to figure . Arrange the papers with their long edge parallel to the front of the bench and turn up the long edge of each paper to about one-seventh of its width. Weigh out the powder and place towards the front of the paper. Carry the front of the paper over to the turned up edge, bring the turn up down and then fold this edge forward until it covers about two thirds of the distance to the near edge of the packet. Turn the edges of the packet so that the overlap is equal at both ends. Firm the creases using a clean flexible spatula but avoid excessive pressure which would cause caking of the enclosed powder. The packets are best packed in pairs, flap to flap and restrained with an elastic band. In a well wrapped product there should not be powder within the flaps or folds. When opened by the user, the powder should appear in the centre of the paper, easily available for administration Types of Powders: Bulk powders for internal use. Bulk powders for external use. Simple & compound powder for internal use. Powder enclosed in cachets & capsule. Compressed powders (tablets) Bulk powder for internal use: Dispense in bulk Accuracy isn't important
Contain several dose. Supplied in wide mouthed container. Bulk powder for external use: Supply non potent drug. Supply in cardboard, glass or plastic container. Also in sitter top container. Types: dusting powder Insufflations Snuffs Dentifrices DUSTING POWDER: These are meant for external application on to the skin and are generally applied in a very fine state of subdivision to avoid local irritation. Types: ( i ) Medical (ii) Surgical Medical dusting powders: Uses:- for superficial skin conditions and for antiseptics, anti- pruritic , astringent, antiperspirant , absorbent, protective and lubricant purposes. e.g. dicophane dusting powder zinc and salicylic acid dusting powder zinc, starch and talc dusting powder. Surgical dusting powders: Surgical dusting powders Uses:- in body cavities, on major wounds as a result of burns and umbilical cords of infants. Surgical dusting powders must be sterilized before their use. PowerPoint Presentation: Preparation: Dusting powders are generally prepared by mixing two or more ingredients on of which must be either starch, kaolin or talc as one of the ingredients of the formulations. Talc and kaolin are commonly used because they are chemically inert. however, since these materials are usually contaminated with pathogenic bacteria, these must be sterilized. e.g. Neosporin powder. Dusting powder: Dusting powder Requirements: 1- Homogenous and very fine 2- Free from irritation. 3- Flow easily. 4- Have good covering capacity. 5- Have good adsorptive and absorptive capacity. 6Spread uniformly over body surface. 7- Cling to skin surface after application. 8- Protect the skin from irritation caused by friction, moisture and chemical irritants. Insufflations: Insufflations Definition: Finely divided powders introduced into body cavities such as ears, nose, throat and vagina. Packaging: Insufflators (powder – blower) : difficult to obtain a uniform dose. Pressure aerosols : for potent drugs where the dose is adjusted and applied through a metered valve. For administration of micronized powders DENTRIFICES (Tooth Powders):
DENTRIFICES (Tooth Powders) Dentrifices are preparations which are generally used with the help of tooth brush for cleansing the surfaces of the teeth. They are available in the form of fine powders and pastes. They contain 1. a suitable detergent or soap 2. some abrasive substance like calcium sulfate, magnesium carbonate, sodium carbonate in fine powder. 3. sweetening agent e.g. saccharin sodium 4. a suitable flavour e.g. peppermint oil, clove oil. snuffs: snuffs These are finely divided solid dosage forms of medicament are inhaled into nostrils for its antiseptics,bronchiodilator and decongestion action. simple powder & compound powder for internal use: simple powder & compound powder for internal use simple powder :- contain only one ingredient compound powder :- contain two or more than two substances mix together Cachets: Cachets Enclosure in cachets provides a means of administering nauseous or disagreeable powders in a tasteless form. Cachets are moulded from rice paper, a material made by pouring a mixture of rice flour and water between two, hot. Polished, revolving cylinders; water evaporates and sheet of wafer is formed. Types of cachets:- : Types:- 1)wet seal 2)dry seal Types of cachets:- ) Wet seal cachets: lower half of the cachet is filled with powdered drug. Then the flange of the empty upper half of the cachet is moistened with water, and pressed over the lower half. The cachet is dried for 15 minutes. ii)Dry seal cachets: ii)Dry seal cachets Drug powder is filled in the lower half and the upper half is pressed over it just like a capsule. Use: They are used for administering the drug with unpleasant taste and a large dose. Before administration, a cachet should be immersed in water for few seconds and then placed on the tongue and swallowed with water. e.g. Sodium aminosalicylate cachets Sodium aminosalicylate and isoniazid cachtets . Molded Tablets : Molded Tablets Molded tablets are generally prepared by mixing the active drug with lactose, dextrose, sucrose, mannitol , or some other appropriate diluent that can serve as the base. This base must be readily water soluble and should not degrade during the tablet's preparation. Lactose is the preferred base but mannitol adds a pleasant, cooling sensation and additional sweetness in the mouth. PowerPoint Presentation: Tablet triturate molds are made of metal. There are two plates, the cavity plate is the plate that has only holes and the peg plate that has pegs. The mold will indicate the capacity of one cavity in the cavity plate but that indication is only an approximation. Typical die plate cavity sizes are 60 mg and 100 mg. Preparation of powders:
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 Mixing of powder 1) spatulation 2)trituration 3)geometric dilution 4)sifting 5)tumbling : Mixing of powder 1) spatulation 2) trituration 3)geometric dilution 4)sifting 5)tumbling Mixing of powder: Mixing of powder Problems encountered in powder formulation: Problems encountered in powder formulation 1- Hygroscopic and Deliquescent Powder Problem: 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 packets C- Addition of light magnesium oxide to reduce the tendency to damp DAddition of adsorbent materials such as starch Examples: - halide salts (ex. Sod. Iodide) Certain alkaloids ( physostigmine Hcl ) Problems encountered in powder formulation: Problems encountered in powder formulation 2- Efflorescent powders Problem: 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: Alumatropine sulfate- citric acid- codeine phosphate … Solution: Using the anhydrous form and treating it in a manner similar to hygroscopic powders Problems encountered in powder formulation: Problems encountered in powder formulation 3- Eutectic Mixtures Problem: 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 powder B- dispensing the components of the eutectic mixture separately. Problems encountered in powder formulation: Problems encountered in powder formulation 4- Incorporation of Liquids Solution: 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 5- Incorporation of Extracts Problem: Some extracts are available as powders or as semisolid. Solution: A- The powdered extracts have no problems and treated generally as powders B- Semisolid extract should be mixed with an equal quantity of lactose and reduced to a dry powder by evaporation before incorporation with other ingredients C- Careful heating if present to save potency of the extract. Problems encountered in powder formulation: Problems encountered in powder formulation 6- Potent Drug Problem: 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 10%w/w drug triturates. B- Very fine powders should be used in the triturates C- Geometric dilution to prepare drug triturates
Problems encountered in powder formulation: Problems encountered in powder formulation 7- Incompatible salts Problem: Chemically incompatible salts when triturated together produce discoloration, chemical deterioration or loss of potency. Solution: A- Compounding such substances with minimum pressure B- 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. Problems encountered in powder formulation: Problems encountered in powder formulation 8- Explosive mixtures Problem: 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. Hypochlorites - sulfides- sulfur- tannic acid- charcoal). Solution: A- Comminute each salt separately. B- Subject to a minimum pressure. 1- Effervescent 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 Effervescent Granules: Effervescent Granules Definition: Sweetened effervescent powders formulated as granules. Granulation: 1- Wet method: By the addition of a binding liquid (Alcohol is frequently used). 2Dry method: Heating effloresced powder to liberate the water of crystallization which is act as the binding agent Effervescent Granules: Effervescent Granules Ingredients used; ( i ) Sodium bicarbonate: It reacts with the acids when the preparation is added to water. The evolved carbondioxide produces effervescence. (ii) Citric acid and tartaric acid: The quantity of these is slightly more than is necessary to neutralise the sodium bicarbonate because effervescent preparations are more palatable if slightly acidic. Tartaric acid is anhydrous but citric acid has one molecule of water of crystallization. heating liberates this water and the moist condition thus produced allows partial interaction between the acids and bicarbonates, during which more water is formed Effervescent Granules: Effervescent Granules The water of crystallization of the citric acid and the water from the reactions makes the material coherent. (iii) Medicaments: often inorganic salts containing water of crystallization are incorporated. e.g. magnesium and sodium sulphates , sodium phosphate and lithium citrate. Effervescent Granules: Effervescent Granules Wet Granulation Procedure: 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 50 º C. 5- The granules are packed in air tight containers Effervescent Granules: Effervescent Granules Dry granulation Procedure: 1- All ingredients except citric acid 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 (99- 105 º C). Upon heating citric acid crystals, the water of crystallization effloresces and citric acid transforms to the powder form Dry granulation: Dry granulation Follow, Procedure: 4- The use of a water bath surrounding the beaker 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 dr ied. Effervescent Granules: Effervescent Granules Use: Before administration, the desired quantity is dissolved in water, the acid and bicarbonate react together producing effervescence. The carbonated water produced from the release of carbondioxide serves to mask the bitter and saline taste of drugs. More over carbondioxide stimulates the flow of gastric juice and helps absorption of medicament. Effervescent Granules: 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. Weighing technique for the dispensing balance: Weighing technique for the dispensing balance 1. The balances should always be sited on a convenient level surface away from the influence of draughts. 2. Clean the balance and pans as necessary. A clean sheet of white demy paper should be placed under the pans helps to contain spillage and protect the balan ce. PowerPoint Presentation: 3 . Select a suitable weighing vessel or paper. Balance pans are usually made of glass or stainless steel and are resistant to direct contact with most medicaments with a few exceptions. Weighing papers are convenient for bulky powders and may facilitate transfer from the balance. For greasy or waxy constituents, greaseproof paper should be used since white demy partly absorbs greasy substances and transfer from the paper is difficult. Small lightweight disposable weighing boats are a useful alternative to weighing papers since they may also be used for viscous substances such as coal tar and for non-viscous liquids PowerPoint Presentation:
If containers such as glass beakers or porcelain evaporating dishes are used as weighing vessels care should be taken to avoid exceeding the total (50g) capacity of the balance. PowerPoint Presentation: 4. Check that the pointer is on the null point but is able to move freely. Counter balance the weighing vessel if necessary. 5. Place the required weights on the left-hand pan – use forceps to avoid contamination of the weights with consequent alteration in mass (especially small weights) 6. Close the balance drawer. This prevents spills from contaminating PowerPoint Presentation: 7 . Collect the medicament from the shelf. Check the label word for word with the formula. 8. Hold the bottle in the left hand. Keep the label uppermost so that it is visible during weighing. 9. Remove the lid or stopper. If possible hold the stopper between the little finger and the palm of the right hand. The thumb and remaining fingers of the right hand remain free to use a spatula. If it is not possible to hold the lid, it should be placed top uppermost on a clean tile to protect against contamination. PowerPoint Presentation: 10. Use a spatula to transfer the medicament to the right hand pan until the pointer returns to the null point. Powders should not be shaken onto the pan from the container. 11. Close the stock container 12. Recheck the weights and the medicament against the formula. :
Contain several dose. Supplied in wide mouthed container. Bulk powder for external use: Supply non potent drug. Supply in cardboard, glass or plastic container. Also in sitter top container. Types: dusting powder Insufflations Snuffs Dentifrices DUSTING POWDER: These are meant for external application on to the skin and are generally applied in a very fine state of subdivision to avoid local irritation. Types: ( i ) Medical (ii) Surgical Medical dusting powders: Uses:- for superficial skin conditions and for antiseptics, anti- pruritic , astringent, antiperspirant , absorbent, protective and lubricant purposes. e.g. dicophane dusting powder zinc and salicylic acid dusting powder zinc, starch and talc dusting powder. Surgical dusting powders: Surgical dusting powders Uses:- in body cavities, on major wounds as a result of burns and umbilical cords of infants. Surgical dusting powders must be sterilized before their use. PowerPoint Presentation: Preparation: Dusting powders are generally prepared by mixing two or more ingredients on of which must be either starch, kaolin or talc as one of the ingredients of the formulations. Talc and kaolin are commonly used because they are chemically inert. however, since these materials are usually contaminated with pathogenic bacteria, these must be sterilized. e.g. Neosporin powder. Dusting powder: Dusting powder Requirements: 1- Homogenous and very fine 2- Free from irritation. 3- Flow easily. 4- Have good covering capacity. 5- Have good adsorptive and absorptive capacity. 6Spread uniformly over body surface. 7- Cling to skin surface after application. 8- Protect the skin from irritation caused by friction, moisture and chemical irritants. Insufflations: Insufflations Definition: Finely divided powders introduced into body cavities such as ears, nose, throat and vagina. Packaging: Insufflators (powder – blower) : difficult to obtain a uniform dose. Pressure aerosols : for potent drugs where the dose is adjusted and applied through a metered valve. For administration of micronized powders DENTRIFICES (Tooth Powders):
DENTRIFICES (Tooth Powders) Dentrifices are preparations which are generally used with the help of tooth brush for cleansing the surfaces of the teeth. They are available in the form of fine powders and pastes. They contain 1. a suitable detergent or soap 2. some abrasive substance like calcium sulfate, magnesium carbonate, sodium carbonate in fine powder. 3. sweetening agent e.g. saccharin sodium 4. a suitable flavour e.g. peppermint oil, clove oil. snuffs: snuffs These are finely divided solid dosage forms of medicament are inhaled into nostrils for its antiseptics,bronchiodilator and decongestion action. simple powder & compound powder for internal use: simple powder & compound powder for internal use simple powder :- contain only one ingredient compound powder :- contain two or more than two substances mix together Cachets: Cachets Enclosure in cachets provides a means of administering nauseous or disagreeable powders in a tasteless form. Cachets are moulded from rice paper, a material made by pouring a mixture of rice flour and water between two, hot. Polished, revolving cylinders; water evaporates and sheet of wafer is formed. Types of cachets:- : Types:- 1)wet seal 2)dry seal Types of cachets:- ) Wet seal cachets: lower half of the cachet is filled with powdered drug. Then the flange of the empty upper half of the cachet is moistened with water, and pressed over the lower half. The cachet is dried for 15 minutes. ii)Dry seal cachets: ii)Dry seal cachets Drug powder is filled in the lower half and the upper half is pressed over it just like a capsule. Use: They are used for administering the drug with unpleasant taste and a large dose. Before administration, a cachet should be immersed in water for few seconds and then placed on the tongue and swallowed with water. e.g. Sodium aminosalicylate cachets Sodium aminosalicylate and isoniazid cachtets . Molded Tablets : Molded Tablets Molded tablets are generally prepared by mixing the active drug with lactose, dextrose, sucrose, mannitol , or some other appropriate diluent that can serve as the base. This base must be readily water soluble and should not degrade during the tablet's preparation. Lactose is the preferred base but mannitol adds a pleasant, cooling sensation and additional sweetness in the mouth. PowerPoint Presentation: Tablet triturate molds are made of metal. There are two plates, the cavity plate is the plate that has only holes and the peg plate that has pegs. The mold will indicate the capacity of one cavity in the cavity plate but that indication is only an approximation. Typical die plate cavity sizes are 60 mg and 100 mg. Preparation of powders:
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 Mixing of powder 1) spatulation 2)trituration 3)geometric dilution 4)sifting 5)tumbling : Mixing of powder 1) spatulation 2) trituration 3)geometric dilution 4)sifting 5)tumbling Mixing of powder: Mixing of powder Problems encountered in powder formulation: Problems encountered in powder formulation 1- Hygroscopic and Deliquescent Powder Problem: 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 packets C- Addition of light magnesium oxide to reduce the tendency to damp DAddition of adsorbent materials such as starch Examples: - halide salts (ex. Sod. Iodide) Certain alkaloids ( physostigmine Hcl ) Problems encountered in powder formulation: Problems encountered in powder formulation 2- Efflorescent powders Problem: 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: Alumatropine sulfate- citric acid- codeine phosphate … Solution: Using the anhydrous form and treating it in a manner similar to hygroscopic powders Problems encountered in powder formulation: Problems encountered in powder formulation 3- Eutectic Mixtures Problem: 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 powder B- dispensing the components of the eutectic mixture separately. Problems encountered in powder formulation: Problems encountered in powder formulation 4- Incorporation of Liquids Solution: 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 5- Incorporation of Extracts Problem: Some extracts are available as powders or as semisolid. Solution: A- The powdered extracts have no problems and treated generally as powders B- Semisolid extract should be mixed with an equal quantity of lactose and reduced to a dry powder by evaporation before incorporation with other ingredients C- Careful heating if present to save potency of the extract. Problems encountered in powder formulation: Problems encountered in powder formulation 6- Potent Drug Problem: 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 10%w/w drug triturates. B- Very fine powders should be used in the triturates C- Geometric dilution to prepare drug triturates
Problems encountered in powder formulation: Problems encountered in powder formulation 7- Incompatible salts Problem: Chemically incompatible salts when triturated together produce discoloration, chemical deterioration or loss of potency. Solution: A- Compounding such substances with minimum pressure B- 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. Problems encountered in powder formulation: Problems encountered in powder formulation 8- Explosive mixtures Problem: 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. Hypochlorites - sulfides- sulfur- tannic acid- charcoal). Solution: A- Comminute each salt separately. B- Subject to a minimum pressure. 1- Effervescent 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 Effervescent Granules: Effervescent Granules Definition: Sweetened effervescent powders formulated as granules. Granulation: 1- Wet method: By the addition of a binding liquid (Alcohol is frequently used). 2Dry method: Heating effloresced powder to liberate the water of crystallization which is act as the binding agent Effervescent Granules: Effervescent Granules Ingredients used; ( i ) Sodium bicarbonate: It reacts with the acids when the preparation is added to water. The evolved carbondioxide produces effervescence. (ii) Citric acid and tartaric acid: The quantity of these is slightly more than is necessary to neutralise the sodium bicarbonate because effervescent preparations are more palatable if slightly acidic. Tartaric acid is anhydrous but citric acid has one molecule of water of crystallization. heating liberates this water and the moist condition thus produced allows partial interaction between the acids and bicarbonates, during which more water is formed Effervescent Granules: Effervescent Granules The water of crystallization of the citric acid and the water from the reactions makes the material coherent. (iii) Medicaments: often inorganic salts containing water of crystallization are incorporated. e.g. magnesium and sodium sulphates , sodium phosphate and lithium citrate. Effervescent Granules: Effervescent Granules Wet Granulation Procedure: 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 50 º C. 5- The granules are packed in air tight containers Effervescent Granules: Effervescent Granules Dry granulation Procedure: 1- All ingredients except citric acid 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 (99- 105 º C). Upon heating citric acid crystals, the water of crystallization effloresces and citric acid transforms to the powder form Dry granulation: Dry granulation Follow, Procedure: 4- The use of a water bath surrounding the beaker 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 dr ied. Effervescent Granules: Effervescent Granules Use: Before administration, the desired quantity is dissolved in water, the acid and bicarbonate react together producing effervescence. The carbonated water produced from the release of carbondioxide serves to mask the bitter and saline taste of drugs. More over carbondioxide stimulates the flow of gastric juice and helps absorption of medicament. Effervescent Granules: 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. Weighing technique for the dispensing balance: Weighing technique for the dispensing balance 1. The balances should always be sited on a convenient level surface away from the influence of draughts. 2. Clean the balance and pans as necessary. A clean sheet of white demy paper should be placed under the pans helps to contain spillage and protect the balan ce. PowerPoint Presentation: 3 . Select a suitable weighing vessel or paper. Balance pans are usually made of glass or stainless steel and are resistant to direct contact with most medicaments with a few exceptions. Weighing papers are convenient for bulky powders and may facilitate transfer from the balance. For greasy or waxy constituents, greaseproof paper should be used since white demy partly absorbs greasy substances and transfer from the paper is difficult. Small lightweight disposable weighing boats are a useful alternative to weighing papers since they may also be used for viscous substances such as coal tar and for non-viscous liquids PowerPoint Presentation:
If containers such as glass beakers or porcelain evaporating dishes are used as weighing vessels care should be taken to avoid exceeding the total (50g) capacity of the balance. PowerPoint Presentation: 4. Check that the pointer is on the null point but is able to move freely. Counter balance the weighing vessel if necessary. 5. Place the required weights on the left-hand pan – use forceps to avoid contamination of the weights with consequent alteration in mass (especially small weights) 6. Close the balance drawer. This prevents spills from contaminating PowerPoint Presentation: 7 . Collect the medicament from the shelf. Check the label word for word with the formula. 8. Hold the bottle in the left hand. Keep the label uppermost so that it is visible during weighing. 9. Remove the lid or stopper. If possible hold the stopper between the little finger and the palm of the right hand. The thumb and remaining fingers of the right hand remain free to use a spatula. If it is not possible to hold the lid, it should be placed top uppermost on a clean tile to protect against contamination. PowerPoint Presentation: 10. Use a spatula to transfer the medicament to the right hand pan until the pointer returns to the null point. Powders should not be shaken onto the pan from the container. 11. Close the stock container 12. Recheck the weights and the medicament against the formula. :
