Dispensing of Emulsions

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Dispensing of Emulsions:

Dispensing of Emulsions By Dr. Muhammad Akbar Pharm.D ( R.Ph ) Lecturer at MIIPS M. Phil scholar

Definition:

Definition An emulsion is essentially a liquid preparation containing a mixture of oil and water that is rendered homogeneous by the addition of an emulsifying agent. The emulsifying agent ensures that the oil phase is finly dispersed throughout the water as minute globules. This type of emulsion is termed an ‘oil-in-water’ emulsion. The oily phase (disperse phase) is dispersed through the aqueous phase (continuous phase). Generally all oral dose emulsions tend to be oil-in-water as the oily phase is usually less pleasant to take and more difficult to flavor . ‘Water-in-oil’ emulsions can be formed but these tend to be those with external uses.

Advantages of emulsions as dosage forms:

Advantages of emulsions as dosage forms Unpalatable oils can be administered in palatable form. Unpalatable oil-soluble drugs can be administered in palatable form. The aqueous phase is easily flavored. The oily sensation is easily removed. The rate of absorption is increased. It is possible to include two incompatible ingredients, one in each phase of the emulsion.

Disadvantages of emulsions as dosage forms:

Disadvantages of emulsions as dosage forms Preparation needs to be shaken well before use. A measuring device is needed for administration. A degree of technical accuracy is needed to measure a dose. Storage conditions may affect stability. Bulky, difficult to transport and prone to container breakages. Liable to microbial contamination which can lead to cracking.

Stability of emulsions:

Stability of emulsions Emulsions can break down in the following ways: Cracking Creaming Phase inversion.

Cracking:

Cracking This is the term applied when the disperse phase coalesces and forms a separate layer. Re-dispersion cannot be achieved by shaking and the preparation is no longer an emulsion. Cracking can occur if the oil turns rancid during storage. The acid formed denatures the emulsifying agent, causing the two phases to separate. Possible reasons for problem: Incompatible emulsifying agent Decomposition of the emulsifying agent Change of storage temperature. Can the emulsion be saved? The emulsion will not reform on shaking.

Creaming:

Creaming In creaming, the oil separates out, forming a layer on top of the emulsion, but it usually remains in globules so that it can be re-dispersed on shaking (e.g. the cream on the top of a pint of milk). This is undesirable as the product appearance is poor and if the product is not adequately shaken there is a risk of the patient obtaining an incorrect dose. Creaming is less likely to occur if the viscosity of the continuous phase is increased. Possible reasons for problem Lack of stability of the system. Product not homogeneous. Can the emulsion be saved? The emulsion will reform on shaking

Phase inversion:

Phase inversion This is the process when an oil-in-water emulsion changes to a water-in-oil emulsion or vice versa. For stability of an emulsion, the optimum range of concentration of dispersed phase is 30–60% of the total volume. If the disperse phase exceeds this, the stability of the emulsion is questionable. As the concentration of the disperse phase approaches a theoretical maximum of 74% of the total volume, phase inversion is more likely to occur. Possible reason for problem Amount of disperse phase Greater than 74%. Can the emulsion be saved? The emulsion will not reform on shaking.

Methods of preparation:

Methods of preparation Dry Gum Method Wet Gum Method

Preparation of the primary emulsion:

Preparation of the primary emulsion Measure the oil accurately in a dry measure. Transfer the oil into a large dry porcelain mortar, allowing all the oil to drain out. Measure the quantity of aqueous vehicle required for the primary emulsion. Weigh the emulsifying agent and place on the oil in the mortar. Mix lightly with the pestle, just sufficient to disperse any lumps. Caution: over mixing generates heat, which may denature the emulsifying agent and result in a poor product. Add all of the required aqueous vehicle in one addition. Then mix vigorously, using the pestle with a shearing action in one direction. When the product becomes white and produces a clicking sound, the primary emulsion has been formed. The product should be a thick, white cream. Increased degree of whiteness indicates a better-quality product. Oil globules or slicks should not be apparent.

Dilution of the primary emulsion:

Dilution of the primary emulsion Dilute the primary emulsion drop by drop with very small volumes of the remaining aqueous vehicle. Mix carefully with the pestle in one direction. Transfer emulsion to a measure, with rinsing. Add other liquid ingredients if necessary and make up to the final volume.

Choice of container:

Choice of container A plain amber bottle with a child-resistant closure would be most suitable as the preparation is an emulsion for internal use.

Labeling considerations:

Labeling considerations a. Title The product is unofficial , therefore the ollowing title would be suitable: ‘Cod liver oil 30% v/v emulsion’. b Quantitative particulars Each 10 ml contains: Cod Liver Oil BP 3 ml Acacia BP 0.75 g c. Product- specific cautions (or additional labelling requirements) ‘Shake the bottle’ will need to be added to the label as the product is an emulsion and will need shaking before use to ensure an accurate dose is measured. d. Directions to patient – interpretation of Latin abbreviations where necessary ‘Take TWO 5ml spoonfuls THREE times a day before food.’ e . Discard date The product is an emulsion and so will attract a 4-week discard date. f . Sample label (you can assume that the name and address of the pharmacy and the words ‘Keep out of the reach of children’ are pre-printed on the label)

Advice to patient:

Advice to patient The patient would be advised to take two 5 ml spoonfuls three times a day before food. In addition, the discard date and the need to shake the bottle would be highlighted to the patient.

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