Ointment

TITLE: EFFECTS OF DIFFERENT COMPOSITIONS OF MATERIALS ON THE CHARACTERISTICS OF OINTMENT FORMULATION.

 Aims :

 To determine the effects of different composition of base on the physical characteristics of ointments and based on the rate of drug released.

Introduction :

            Ointment formulation is a semisolid dosage form that could be used to apply on the skin. Ointments are composed mostly of fluid hydrocarbons mixed in a matrix of higher melting solid hydrocarbons. The formulation contains one or more active ingredient(s) dissolved or dispersed homogenously in the oily phase. A good ointment formulation needs to have an attractive texture, can be applied easily to skin and high rate of release of its active ingredient.

           Commonly, ointment is made up of an active ingredient (powder or liquid) which is incorporated into an oily semisolid carrier. In pharmaceutics, ointment preparation is used for treatment at the site of application or to exert the emollient effect.

Apparatus :                                                                 

Weighing instrument, weighing boat, 100ml beaker , heater,1 set of cream and spatula, mortar and pestle, dialysis bag (10cm), thread, glass rod, water-bath, 1 set of pipette (5 ml) and pipette-bulb,1 plastic cuvette and spectrophotometer UV/Vis.

Materials:

Emulsifying wax, white soft paraffin, liquid paraffin, acetylsalicylic acid, distilled water

Methods :

1. 50g of Emulsifying Wax was prepared based on the following formulation:

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

2.  5 g of the ointment formed is taken and placed into the weighing boat and then labeled. The texture, clarity and the color of the ointment is described and compared.
3. 5 g of Acetylsalicylic acid powder was incorporated into 30 g of ointment that was prepared by the levigation technique.
   
   
4. Acetylsalicylic acid is then filled into the dialysis bag and the two sides of the bag is made sure to be tied neatly, like the diagram below: 
   
5. The bag is placed into a beaker (100ml) filled with distilled water (50ml) which was already heated to the temperature of 37°C.
   

Question:

1. Compare the physical characteristics of the ointments and characteristics and give elaboration.

Emulsifying Ointment	Material (50g)			Texture of ointment			Clarity	Colour
	Emulsifying Wax	White Soft Paraffin	Liquid Paraffin	Spreadibility	Greasiness	Hardness
I	21	25	4	Most Difficult	Least Greasy	Hardest	Cloudy	White
II	17	25	8	Difficult	Relatively greasy	Hard	Cloudy	White
III	13	25	12	Intermediate	Greasy	Soft	Cloudy	White
IV	9	25	14	Easy	Most Greasy	Softest	Cloudy	White

There was four different formulation of ointments with constant amount of white soft paraffin which is about 25g and different amount of emulsifying wax and liquid paraffin.  Total for this formulation is up to 50g. All ointments formulation has white colour and cloudy appearance. The degree of the clarity was depended on the amount of emulsifying wax contained in the formulation. 

Texture and spreadibility of  ointment affected by composition of emulsifying wax in ointments. The greater the amount of emulsifying wax added, the more difficult of its spreadibility upon application. The greasiness also increases as the increase in the amount of emulsifying wax. The hardness of the final product exactly depends on the amount of emulsifying wax. The lesser the amount of emulsifying wax used, then the softer the ointment produced.

2) Plot a graph of UV absorption against time. Give a review on it.

Time (min)	UV Absorption
	0	5	10	15	20	25	30
UV absorption at 300nm	0.000	0.060	0.124	0.138	0.144	0.203	0.315

From the graph, the UV absorption at 310nm which carried out at 37^oC is proportional to the time throughout the experiment. UV absorption is proportional to the time where acetylsalicylic acid released from the dialysis bag to the distilled water. The longer the time, the higher amount of the drug to pass through the membrane.

            The gradient of the graph refers to the releasing rate of acetylsalicylic acid from the membrane of the dialysis bag. From the graph, the gradient of the graph increases as the time increases until the 25^th minute. At the beginning of the experiment, the higher concentration of acetylsalicylic acid from the dialysis bag move to the lower concentration of distilled water. As the experiment proceeds, the solution in the dialysis bag become isotonic to the distilled water as some portion of the acetylsalicylic acid has been moved to the distilled water. The gradient of the graph has decreased.

            The graphs shows fluctuation because we didn’t stir the distilled water when the samples from the distilled water. Experimental error may be due to improper filling of ointment into the dialysis bag causing the presence of ointment on the surface of dialysis bag. Besides, the threads tying the both ends of the dialysis bag are loosen causing leakage of acetylsalicylic acid from the dialysis bag into the distilled water. There are some precautions needed to be taken. The temperature of the water bath should be maintained at 37^oC to get a uniform temperature. The dialysis bag should be tied tightly and immersed completely in the distilled water. The smooth surface of the cuvette should be cleaned before it is put into the spectrometer. 

3. Plot a graph of UV absorption versus time for ointments that have different compositions. Compare and discuss the results. 

In this experiment, 4 formulation of 50g ointment had been produced, they have different composition of emulsifying wax and liquid paraffin, but constant composition of white soft paraffin. Different composition of emulsifying wax and liquid paraffin used to investigate the permeation of acetylsalicylic acid from the ointment. UV absorption indicates the amount of salicylic acid diffuse out of dialysis bag into water bath.

 The amount of emulsifying wax will affect the permeation of acetylsalicylic acid. The greater the amount of emulsifying wax in ointment formulation, the smaller the amount of acetylsalicylic acid permeate the dialysis bag because emulsifying wax can retard drug release. Thus, the value of UV absorption will be lower. The emulsifying ointment I has greatest amount of emulsifying wax (21g) , thus it has retard the release of salicylic acid from dialysis bag into the water bath. So, the graph of emulsifying ointment I has lowest points than other ointment’s graphs. As amount of emulsifying wax increases from ointment I to IV, thus the graph II, III and IV become progressively higher than I.

Liquid paraffin forms a greasy layer on the skin and inhibits moisture loss. Hydration is effective in encouraging percutaneous absorption of a drug. The higher the composition of liquid paraffin, the higher amount of acetylsalicylic acid diffuse from the dialysis bag into water bath, thus the higher the value of UV absorption. In this experiment, emulsifying ointment IV has greatest amount of liquid paraffin (16g) has greatest release of salicylic acid into water bath. The emulsifying ointment IV has highest points of graph when compared to other graphs of ointments.

Emulsifying ointment I with greatest amount of emulsifying wax and lowest amount of liquid paraffin, has lower permeation of salicylic acid into water bath and achieves lowest value of UV absorption. Emulsifying ointment IV with lowest amount of emulsifying wax and greatest amount of liquid paraffin, has greater permeation of salicylic acid into water bath and achieves highest value of UV absorption. The experimental results match with theory that the drug diffusion should increase with the increase of liquid paraffin and decrease of emulsifying wax. 

4. What is the function of each ingredient using in the preparation of ointments? How the usage of different contents of emulsifying wax and the liquid paraffin influence the physical characteristic of the ointment formulation and its drug releasing rate?

Ingredients	Function
Emulsifying wax	Substance added to an emulsion to prevent the coalescence of the globules of the dispersed phase. They are also known as emulsifiers. They act by reducing the interfacial tension between the two phases and forming a stable interfacial film. It can increase the water solubility of the ointment.
White Soft Paraffin	Known as white petroleum jelly. This is not an active ingredient as such, but works as a moisturiser by providing a layer of oil on the surface of the skin to prevent water evaporating from the skin surface. It is a very greasy to reduce the moisturiser.
Liquid Paraffin	to reduce the viscosity of the base, increase the spreading ability of the acetylsalicylic acid and decrease the hardness of the ointment.
Acetylsalicylic Acid	Is the active ingredient in this ointment preparation and thus, plays a major role in giving the therapeutic effect of the ointment produced. Acetylsalicylic acid which is also known as aspirin will give antipyretic, anti-inflammatory and analgesic effect by inhibiting the enzyme cyclooxygenase irreversibly. It may help to reduce the redness and inflammation of acne, and the grainy texture of the dissolved aspirin also serves to exfoliate the skin.

The composition of the emulsifying wax and liquid paraffin influence the physical characteristic of the ointment formulation and its drug releasing rate. The use of emulsifying wax used to emulsify water and oils together. Usage varies based on the combination of thickeners but normal usage rates are between 3% and 6% of the total weight of the formulation. So, the higher the amount of the emulsifying wax, the greater the capability of the ointment to hold water. The liquid paraffin increases the spreadibility of ointment and decrease the hardness of the ointment. So, the higher the amount of liquid paraffin, the better the drug releasing rate and less hard of the final product formed.

Conclusion: 

Emulsifying wax and liquid paraffin affect physical properties of ointment formulation and drug releasing rate. Emulsifying wax increases the capacity of ointment to hold water, while liquid paraffin increases spreadibility of ointment and drug release rate.

References:

1.     Aulton, M.E. 2002. Pharmaceutics: The science of dosage form design. Edinburgh: Churchill Livingstone
2. Florence,A.T. & Attwood, D. 1998. Physico-chemical principles of pharmacy. 3rd Ed. New York: Macmillan