pharmaceutical Powders

Brain storming What is powder ? What type of powder do you know? What is the clinical importance of powder ? Have you seen how powder is packed?

Objective At the end of this session the learners will able to: Define powder Classify powder Illustrate the importance of powder Compare and contrast each type of powder Prepare and dispense divided powder

Introduction and overview of powders & capsules include solid preparations intended for both internal and external use. Type of Powder preparations Bulk powders for external use _termed dusting powders Bulk oral powders Individual unit dose powders Unit dose capsules.

Types of Powders 1- Divided powders - packets - cachets - capsules 2- Undivided (Bulk) powders - dusting powder - effervescent powder E.g. antacids, laxatives, dietary nutrient supplements…. 5

3. Oral divided powder May contain one or more active ingredients together with an inert diluent to produce a minimum quantity of 120 mg. 4. Oral undivided powder Are usually a simple mixture of the prescribed medication without additional ingredients.

Advantages and disadvantages of Dusting powders as dosage forms Easy to apply Pleasant to use Absorb skin moisture Decreasing skin friction Discouraging bacterial growth Drying action gives cooling effect

Disadvantages May block pores causing irritation Possibility of contamination Light fluffy powders may be inhaled by infants leading to breathing difficulties Not suitable for application to broken skin

Advantages and disadvantages of bulk oral powders as dosage forms May be more stable than liquid equivalent Administered with relative ease Absorption quicker than capsules or tablets

Disadvantages Variable dose accuracy Bulky and inconvenient to carry Difficult to mask unpleasant tastes

General method for preparing dusting powders The method for mixing powders in the formulation of a dusting powder is the standard ‘doubling-up’ technique /geometrical dilution/.

‘Doubling-up’ technique Weigh the powder present in the smallest volume (powder A) and place in the mortar. Weigh the powder present in the next largest volume (powder B) and place on labeled weighing paper. Add approximately the same amount of powder B as powder A in the mortar.

Cont’d Mix well with pestle. Continue adding an amount of powder B that is approximately the same as that in the mortar and mix with the pestle, i.e. doubling the amount of powder in the mortar at each addition. If further powders are to be added, add these in increasing order of volume as in parts 3, 4 and 5 above.

General method of 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.

unit dose powders as dosage forms Advantages more stable than liquid dosage forms accurate dosing Easy to administer Small particle size of drug Acceptable to patients

Disadvantages May be difficult to swallow Hard to mask unpleasant flavors).

unit dose capsules as dosage forms Advantages More stable than liquid dosage forms Accurate dosing Easy to administer Unpleasant tastes easily masked Release characteristics can be controlled Can be made light-resistant Small particle size of drug Acceptable to patients

Disadvantage May be difficult to swallow Unsuitable for very small children Possible patient objections to the use of animal gelatin

Note: The no. Of ingredients may be one (simple powder) or more than ingredient (compound powder).

General method for producing unit dose powders Remember, for ease of handling the minimum weight of powder in a unit dose paper is 200 mg. Calculate to make an excess of the number of powders requested. Determine whether a single or double dilution of the active ingredient is required.

Cont… Mix the active ingredient and the diluents (Lactose BP unless there is a reason not to use it, for example, if the patient is intolerant to lactose or due to instability of the ingredients) in a mortar using the ‘doubling-up’ technique.

Cont’d Work on a clean dry glass tile. Select a suitable size of paper (e.g. 10 ×10 cm), turn in one edge and fold down approximately 1.25 cm. Repeat for the required number of powders. Place the paper on the glass tile, with the folded edge away from the compounder, and each edge slightly overlapping, next to the balance pan to be used for weighing.

Con… Weigh out the individual powder from the bulk powder, and transfer to the centre of the paper (if placed too near the fold, the powder will fall out during opening). Fold the bottom of the powder paper up, and underneath, the flap folded originally. Fold down the top of the paper until it covers about two- thirds of the width of the paper. This top edge of this fold should help to hold the contents of the paper in the centre of the paper.

Cont…. Fold the bottom of the powder paper up to, and underneath, the flap folded originally. Fold down the top of the paper until it covers about two-thirds of the width of the paper. This top edge of this fold should help to hold the contents of the paper in the centre of the paper.

Con… Fold the two ends under, so that the loose ends slightly overlap, and then tuck one flap inside the other Wrap each powder in turn, making sure they are all the same size. Stack the powders in pairs, flap to flap.

Cont’d Tie together with a rubber band (not too tightly). Place in a rigid cardboard box. The label should be placed on the outer pack such that when the patient opens the box, the label is not destroyed.

General method of preparation of capsules Choose an appropriate capsule size for the powder bulk. Normally a capsule size 3 would be chosen and so work on the basis of filling each capsule with 200 mg of powder. Calculate quantities required and make an excess as with the manufacture of individual unit dose powders. Mix using the ‘doubling-up’ technique.

Cont’d Handle the capsules as little as possible as powder fill weights will be inaccurate as a result of contamination with grease and moisture. This is also important for reasons of hygiene. Fill powder into the longer half of the capsule.

Cont…. remember that these capsules are to be swallowed by a patient There are at least three methods of filling capsules manually. Always work on a clean tile: remember that these capsules are to be swallowed by a patient Place some powder on to a piece of weighing paper. Hold the capsule with one hand and lift the paper with the other and scoop the powder into the capsule.

Con…. Place some powder on to a piece of weighing paper and fill the capsule using a chemical spatula. Weigh approximately 200 mg of powder onto a piece of weighing paper which has been folded in half. Use the weighing paper to pour the powder into the capsule.

Example of dusting powder: Ingredient zinc oxide 250 g starch, in powder 250 g purified talc, sterilized 250 g Advice to patient: the powder should be dusting lightly onto the affected area Action and use: absorbent dusting powder, mild antiseptic

Dusting powder zinc oxide 250 g starch, in powder 300 g purified talc, sterilized 750 g Send: 50 gm Use 120 um sieve

Method for preparing Zinc Starch and Talc Dusting Powder BPC Ensure the capsule outer surface is powder-free. Check the weight of the filled capsule. Remember to tare with an empty capsule of the same size so you are only weighing the contents of the capsule (and not including the weight of the capsule itself).

Con…. Weigh 25 g Zinc Oxide BP using a Class II or electronic balance. Weigh 25 g Starch BP using a Class II or electronic balance. Weigh 50 g Purified Talc BP using a Class II or electronic balance.

Cont’d… Transfer the Starch BP to a porcelain mortar. Add the Zinc Oxide BP to the Starch BP in the mortar and mix using a pestle. Add the Purified Talc BP to the powders in the mortar and continue mixing. Transfer the mixed powder to a powder shaker container (Figure below) or an amber glass jar. Label and dispense to the patient

Figure of powder container