COMMINUTION OF DRUGS
•Grinding a drug in a mortar to reduce its particle size is termed trituration or comminution.
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•On a large scale, various types of mills and pulverizers may be used to reduce particle size.
• Through the grinding action of rapidly moving blades in the comminuting chamber, particles are reduced in size and passed through a screen of desired dimension to the collection container.
The collection and containment system:
♧protects the environment from chemical dust
♧reduces product loss
♧prevents product contamination.
Levigation
•Levigation is commonly used in small scale preparation of ointments and suspensions to reduce the particle size and grittiness of the added powders
•A mortar and pestle or an ointment tile may be used.
•A paste is formed by combining the powder and a small amount of liquid (the levigating agent) in which the powder is insoluble.
•The paste is then triturated, reducing the particle size.
•The levigated paste may then be added to the ointment base and the mixture made uniform and smooth by rubbing them together with a spatula on the ointment tile
Mineral oil and glycerin are commonly used levigating agents.
BLENDING POWDERS
•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.
Spatulation (mixing powders using spatula)
- 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.
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.
-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.
-This method is especially indicated when the potent substance and other ingredients are the same color and a visible sign of mixing is lacking.
-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.
-Some pharmacists add an inert colored powder to the diluent before mixing to permit visual inspection of the mixing process.
-For example, if 100mg of potent drug is required to be mixed with 900mg of lactose then according to geometric dilution, the following procedure should be followed:
• 100mg of potent drug + 100mg of lactose = 200mg of mixture,
•200mg of the mixture + 200 mg of lactose= 400 mg of mixture
•400mg of the mixture + 400mg of lactose =800mg of mixture
•800mg of the mixture + remaining portion = 1000mg of mixture of lactose.
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.
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 are mixers that use motorized blades to blend powders in a large vessel.
METHOD FOR PREPARATION OF DIVIDED POWDERS
1)The minimum weight of individually wrapped powder is 120mg. Dilution of drug with a diluent usually lactose is often necessary to produce this weight.
2)Usually tablets or capsules may be used to prepare oral powders. This involves either crushing the tablets in a mortar and pestle,or emptying the contents of the capsule and adding a suitable diluent.
3)Lactose is most commonly used diluent because it is colourless,odourless,soluble,is generally harmless and has good flow properties.
4)Some patients may be unable to tolerate lactose and a suitable inert alternative diluent, for instance light kaolin, would then be used.
Folding of paper
containing potent substances, because homogeneous blending is not as certain as other methods.
Trituration
-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.
-This method is especially indicated when the potent substance and other ingredients are the same color and a visible sign of mixing is lacking.
-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.
-Some pharmacists add an inert colored powder to the diluent before mixing to permit visual inspection of the mixing process.
-For example, if 100mg of potent drug is required to be mixed with 900mg of lactose then according to geometric dilution, the following procedure should be followed:
• 100mg of potent drug + 100mg of lactose = 200mg of mixture,
•200mg of the mixture + 200 mg of lactose= 400 mg of mixture
•400mg of the mixture + 400mg of lactose =800mg of mixture
•800mg of the mixture + remaining portion = 1000mg of mixture of lactose.
Sifting
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•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.
Tumbling
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•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 are mixers that use motorized blades to blend powders in a large vessel.
METHOD FOR PREPARATION OF DIVIDED POWDERS
1)The minimum weight of individually wrapped powder is 120mg. Dilution of drug with a diluent usually lactose is often necessary to produce this weight.
2)Usually tablets or capsules may be used to prepare oral powders. This involves either crushing the tablets in a mortar and pestle,or emptying the contents of the capsule and adding a suitable diluent.
3)Lactose is most commonly used diluent because it is colourless,odourless,soluble,is generally harmless and has good flow properties.
4)Some patients may be unable to tolerate lactose and a suitable inert alternative diluent, for instance light kaolin, would then be used.
Folding of paper
It involves following steps:
(A)The long edge away from the dispenser should be turned over to about one-7th of the paper width.
(B)The powder should be weighed accurately and placed on the paper towards the folded edge of the centre of the paper. (C)The unfolded long edge should then be brought over the powder to meet the crease of the folded edge and the flap closed over it.
This topic is very easy and interesting hope you enjoyed reading. Powders, its advantages & disadvantages do read this topic also as it is the part 1. Thank you
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