3. OINTMENT

Title:

Evaluation of the impact of different content on the characteristics of an ointment formulation.

Objectives:

1.      To study the effects of different ointment composition on the physical characteristics of the ointment formed.

2.      To determine the rate of drug release from the formulation of ointment.

Introduction:

Ointments are semisolid preparations intended for external application to the skin or mucous membranes. An ointment is an oily base preparation and consists of one or more drugs distributed homogenously in base and can be absorbed through the skin for systemic action. Ointments are formulated using hydrophobic, hydrophilic, or water-emulsifying bases to provide preparations that are immiscible, miscible, or emulsifiable with skin secretion. Ointments are used topically for several purposes, such as protectants, antiseptics, emollients, antipruritics, kerotolytics, and astringents. The vehicle or base of an ointment is of prime importance if the finished product is expected to function as any one of the above categories. In the case of a protective ointment, it serves to protect the skin against moisture, air, sun rays and other external factors. It is necessary that the ointment neither penetrates the human skin barriers nor facilitates the absorption of substances through this barrier. An antiseptic ointment is used to destroy or inhibit the growth of bacteria. Frequently bacterial infections are deeply seated; a base which has the capacity to either penetrate or dissolve and release the medication effectively is therefore desired. Ointments used for their emollient effect should be easy to apply, be non-greasy and effectively penetrate the skin.

Apparatus:

The apparatus required were a measuring cylinder, a weighing boat, a 100ml beaker, heater, a set of slap & spatula, a set of mortar & pestle, a dialysis bag (10cm), 2 threads, a glass rod, water-bath, a set of pipette (5ml) and a pipette-bulb, a plastic cuvette and spectrophotometer UV/Vis.

Materials:

The materials required were emulsifying wax, white soft paraffin, liquid paraffin, acetylsalicylic acid and distilled water.

Procedures:

Emulsifying ointment	Ingredients (g)			Total (g)
	Emulsifying wax	White soft paraffin	Liquid paraffin
I	21	25	4	50
II	17	25	8	50
III	13	25	12	50
IV	9	25	16	50

50g of emulsifying ointment is prepared through formulation as above:

5g of ointment form is taken from the total of 50g and is placed in weighing boat and is labeled. The texture, clarity and colour of ointment is observed and compared.

1.5g of Acetylsalicylic acid is incorporated into 30g of made ointment by using levigation. (Acetylsalicylic acid powder is crushed into finer particles using mortar and pestle if required.)

The Acetylsalicylic acid ointment is filled into dialysis bag. Both ends of the bag are being tied.

The dialysis bag is placed into 100ml beaker which contains 50ml of saline water and is heated in water-bath to 37ºC.

With the interval of each 5 minutes, 3-4mL of the distilled water is pipetted out. The release of acetylsalicylic acid from the ointment is determined by using UV-visible spectrometer. Distilled water is stirred before the taking the sample.

Time (min)	UV Absorption
	0	5	10	15	20	25	30	35	40	45
UV absorption at 310nm	0	0.107	0.046	0.099	0.108	0.118	0.143	0.176	0.210	0.193

Result and Discussion:

1)Compare the physical appearance of the ointment and give your reasons.

Emulsifying ointment	Texture			Clarity	Colour
	Spreadibility	Greasiness	Hardness
I	+	+	++++	Not clear	White
II	++	++	+++	Not clear	White
III	+++	+++	++	Not clear	White
IV	++++	++++	+	Not clear	White

In this experiment, four types of emulsifying ointment have been prepared. Emulsifying ointment I consist of 21g emulsifying wax, 25g white soft paraffin and 4g liquid paraffin. Emulsifying ointment II consist of 17g emulsifying wax, 25g white soft paraffin and 8g liquid paraffin. Emulsifying ointment III consist of 13g emulsifying wax, 25g white soft paraffin and 12g liquid paraffin. Meanwhile emulsifying ointment IV consists of 9g emulsifying wax, 25g white soft paraffin and 16g liquid paraffin.

These four types of emulsifying ointment shared similar characteristic in the term of clarity and color of the ointment which is not clear and white in color.

Based on the table, we can see that Emulsifying Ointment IV is the most spreadable, followed by Emulsifying Ointment III, and Emulsifying Ointment II. Emulsifying Ointment I is poorly spread. For the greasiness of the ointment, Emulsifying IV is very greasy, followed by Emulsifying Ointment III, and Emulsifying Ointment II. Emulsifying Ointment I is the least greasy. Meanwhile, for the hardness of ointment, Emulsifying I is the hardest followed by Emulsifying Ointment II and Emulsifying Ointment III. Emulsifying ointment IV is very soft.

The content of emulsifying wax in the ointment tends to give stability to the ointment by binding the water and oil together permanently. Thus, higher content of emulsifying wax will cause less spreadibility of the ointment. Meanwhile, liquid paraffin contributes to the greasiness the ointment. High proportion of liquid paraffin will cause the ointment to become greasier but decrease the hardness. All emulsifying ointments are white in color because liquid paraffin have characteristic of colorless liquid and clear.

2)Plot the graph of UV absorption against time. Give explanation.

Time (min)	UV Absorption
	0	5	10	15	20	25	30	35	40	45
UV absorption at 310nm	0	0.031	0.046	0.099	0.108	0.118	0.143	0.176	0.210	0.193

In this experiment, UV-visible spectrometer is used to determine the release of Acetylsalicylic acid from the ointment formulation. The Acetylsalicylic acid ointment is filled into dialysis bag. Both ends of the bag are being tied and placed into heated water-bath. The UV absorptions are measured with the interval of each 5 minutes.

Based on the graph above, it is shown that the value of UV absorption increases with time which means, the concentration of Acetylsalicylic acid in the water-bath increases as the time increases. This means that the drugs (Acetylsalicylic acid) are passing through the membrane of dialysis bag. However, at 0 minute, the graph has shows the present of Acetylsalicylic acid in the distilled water. This might be due to some errors occur during conducting the experiment such as leakage of the ointment from the dialysis bag because not properly tie the bag. Moreover, at minute 45, the graph shows a lower value of absorption. Errors might occur at this stage such as uneven stirring of the distilled water which can disturb uniform distribution of drugs throughout the distilled water. So, this causes the result not accurate.

There are some precaution steps that should be taken during conducting the experiment. Firstly, tie the dialysis bag with thread tightly in order to prevent leakage of Acetylsalicylic acid from the bag. Secondly, stir the distilled water evenly so that amount of drugs distributed is uniform.

3)What is the function of each ingredients used in the preparation of the ointment? How does the usage of different compositions of the emulsifying wax and liquid paraffin affects the physical properties of the ointment and the rate of drug release from it?

Emulsifying wax is one of the essential ingredients in making ointments. It emulsifies water and oils together. In this case, emulsifying wax binds all of the ointment ingredients. It also provides stability in the ointment. Liquid paraffin is use to reduce the viscosity of ointment and soften the ointment. Meanwhile, white soft paraffin is used as an emollient base in the ointment formulation.

The content of emulsifying wax in the ointment tends to give stability to the ointment by binding the water and oil together permanently. Thus, higher content of emulsifying wax will cause rate of drug release from it to decrease as it contributes to the hardness of ointment. Meanwhile, liquid paraffin contributes to the greasiness of the ointment. High proportion of liquid paraffin will cause the ointment to become greasier but decrease the hardness. Thus increase the rate of drug release. So, a correct proportion of emulsifying wax and liquid paraffin is needed in order to have good drug release.

Conclusion

The different amount of ingredients in the ointment formulation will affect the physical property and the rate of drug release from the ointment.

References

1. http://pharmlabs.unc.edu/labs/ointments/intro.htm
2. Michael E. Aulton (2007) Aulton’s Pharmaceutics the Design and Manufacture of Medicines, Third Edition Churchill Livingstone Elsevier, New York.