OINTMENT

Title
Assessment on the Impact of Different Ingredients on the Characteristics of an Ointment Formulations

Date
26th March 2015

Objectives

• To investigate the effect of different types of ointment composition on the physical properties of ointment formed.
• To investigate the rate of release of active ingredient from the ointment. 

Introduction           

          Ointment is a smooth oily preparation that is rubbed on the skin for medical purposes or as cosmetic purposes.  It is also a homogeneous, viscous, semi-solid preparation, most commonly a greasy, tick oil with a general composition of 80% of oil and 20% of water.

          The vehicle of an ointment is known as ointment bases.  They are different types of ointment bases like hydrocarbon bases, absorption bases, water soluble bases, emulsifying bases and vegetable oils.  The medicaments are dispersed in the base of the ointment and later they get divided after the drug penetration into the living cells of the skin.

          The characteristics of good ointment are it has a good texture, easy to be applied to the skin and higher rate of release of active ingredient from the bases.  In the industry of pharmaceutics, ointment is being used on the skin as topical application and to increase the moisture of the skin or better known as the emollient effect.

Apparatus 

1. Weighing balance
2. Weighing boat
3. A 100ml beaker 
4. Heater
5. A set of slap and spatula
6. A set of mortar and pestle
7. A dialysis beg of 10cm
8. 2 string of thread
9. A glass rod
10. Water-bath
11. A set of pipette of 5ml and pipette-bulb
12. A cuvette plastic
13. Spectrophotometer UV/Visible

Materials 

1. Emulsifying wax
2. White soft paraffin
3. Liquid paraffin 
4. Acetylsalicylic acid
5. Distilled water

Procedures

1. Emulsifying ointment of 50g is prepared according to the formula below:

Emulsifying ointment	Groups	Material (g)			Total (g)
		Emulsifying wax	White soft paraffin	Liquid paraffin
I	1.5	21	25	4	50
II	2,6	17	25	8	50
III	3,7	13	25	12	50
IV	4,8	9	25	16	50

2. A small amount of ointment is taken out and put on the weighing boat and labeled. The ointment was compared with other ointments prepared according to its texture, clarity and colour obtained.

3. Acetylsalicylic acid (1.5g) is incorporated into 10g of prepared ointment using levigation method. (grind acetylsalicylic acid with mortar and pestle for a finer texture if necessary )

4. Acetylsalicylic acid ointment is filled in the dialysis bag and ensure both the ends are tied correctly with the thread.

5. The dialysis beg is put into 100ml beaker filled with 50ml of distilled water which is heated until temperature of 37 degree Celsius.

6. An aliquot sample of 3-4ml is pipetted out for every 5 minute and the release of Acetylsalicylic acid from the ointment is determined using Spectrophotometer UV/Visible.  Distilled water is stirred with glass rod before sample is being taken out.

Results

Time (min)			UV absorption at 300nm
			0	5	10	15	20	25	30
Emulsifying ointment	I	1	0.004	0.007	0.011	0.028	0.032	0.037	0.049
		5	0.052	0.073	0.193	0.211	0.274	0.339	0.369
	II	2	0.222	0.252	0.304	0.322	0.410	0.470	0.517
		6	0.019	0.089	0.115	0.162	0.190	0.204	0.275
	III	3	0.064	0.081	0.097	0.095	0.106	0.115	0.121
		7	0.000	0.032	0.047	0.045	0.052	0.074	0.084
	IV	4	0.104	0.111	0.119	0.155	0.162	0.191	0.221
		8	0.000	0.031	0.051	0.070	0.098	0.130	0.174

Questions

1. Compare the physical properties of ointment. Give reason.

         From this experiment, there are four types of ointments prepared with different portion of emulsifying wax and liquid paraffin and fixed amount of white soft paraffin. The physical properties which can be compared among these four products are greasiness, spreadibility and hardness.

        By comparing the hardness of these four products, the descending sequence is emulsifying ointment I, emulsifying ointment II, emulsifying ointment III and emulsifying ointment IV. The emulsifying ointment I is the hardest as it has the largest amount of emulsifying wax which has the characteristics of cetyl alcohol combined with the viscosity building effect of stearyl alcohol as an effective thickener and helps form stable product. The larger amount of emulsifying wax added, the harder the ointment.

        For the greasiness, the emulsifying ointment IV is the greasiest, followed by emulsifying ointment III, emulsifying ointment II and emulsifying ointment I because the emulsifying ointment IV has the largest amount of liquid paraffin. The liquid paraffin is a very highly refined mineral oil. Hence, the larger volume of liquid paraffin added, the greasier the ointment.

       As the emulsifying ointment IV has the largest amount of liquid paraffin, it is the most spreadable ointment. Then, it is followed by emulsifying ointment III, emulsifying ointment II and emulsifying ointment I is the least spreadable ointment. This can be seen that the characteristic of the liquid paraffin which acts as emollient and provides the liquid properties to the ointment. Therefore, the larger volume of liquid paraffin added, the more spreadable the ointment.

      In conclusion, we must balance the composition of Emulsifying Wax and Paraffin Oil To prepare an ideal ointment so that the ointment produced is not too hard and not too soft.

2. Plot graph of UV absorption against time and give explanation.

Time (min)	UV absorption
	0	5	10	15	20	25	30
UV absorption at 300nm	0.004	0.007	0.011	0.028	0.032	0.037	0.049

In this experiment, UV spectrometer is used to measure the rate of acetylsalicylic acid release from the ointment in the dialysis bag to the distilled water by simple diffusion from high concentration to lower concentration. The temperature of distilled water is maintained at 37⁰C to mimic the temperature of human body. UV absorption refers to the amount of drug that passes through the membrane. From the graph plotted above, it shows that as the time increases, the concentration of the acetylsalicylic acid in the distilled water is increasing. It shows gradual increase of UV absorption. The longer the time, the higher the rate of UV absorption and thus, the higher the concentration of drug diffuses out of the bag through the membrane. As time goes by, more acetylsalicylic acid is present outside, thus the higher the UV absorption.

     There are some precautions that can be taken during conducting the experiment which are removing any residual at the both end of dialysis bag in the distilled water in order to get accurate result. Next, at both end of dialysis bag, the rope must be tightened tightly to prevent any leakage of the ointment and the dialysis bag should also be immersed completely in the distilled water. During conducting the experiment, the distilled water should not be over stirred. This is because, the dialysis bag may break and lots of ointment will be released from the dialysis bag. The cuvette should also be cleaned from any finger print so that the measurement is correct. The temperature must be controlled in order to get the human body temperature at 37^oC.

3. Plot a graph of UV absorption against time for ointment formulation which contain different ingredients. Compare and discuss the results.

Time (min)			UV absorption at 300nm (Mean ± SD)
			0	5	10	15	20	25	30
Emulsifying ointment	I		0.028 ± 0.024	0.040 ± 0.033	0.102 ± 0.091	0.120 ± 0.092	0.153 ± 0.121	0.188 ± 0.151	0.209 ± 0.160
	II		0.121 ± 0.102	0.171 ± 0.082	0.210 ± 0.095	0.242 ± 0.080	0.300 ± 0.110	0.337 ± 0.133	0.396 ± 0.121
	III		0.032 ± 0.032	0.0565 ± 0.0245	0.072 ± 0.025	0.07 ± 0.025	0.079 ± 0.027	0.0945 ± 0.0205	0.1025 ± 0.0185
	IV		0.052 ± 0.052	0.071 ± 0.040	0.085 ± 0.034	0.113 ± 0.043	0.130 ± 0.032	0.161 ± 0.031	0.198 ± 0.024

From the graph above, the formulation IV has the highest UV absorption at 300nm, which means it has the highest concentration of acetylsalicylic acid in the distilled water, followed by formulation III, II, and I. This states that the longer the ointment stay in the water bath, the more acetylsalicylic acid will be diffuse out of dialysis bag, so more UV will be absorbed. Besides, the highest proportion concentration of acetylsalicylid acid should be produced in the formulation with the highest proportion of liquid paraffin and lowest proportion of emulsifying wax, which is formulation IV.

        Emulsifying wax is water miscible base, while liquid paraffin is hydrocarbon base. Emulsifying wax helps in dispersing the hydrophilic acetylsalicylic acid, while liquid paraffin assist in diffusion of acetylsalicylic acid out of the ointment through dialysis bag into the distilled water. With high proportion of emulsifying wax and low proportion of liquid paraffin, formulation I is the hardest among the four formulations and should has the slowest release rate. Acetylsalicylid acid is hydrophilic, therefore it disperses well in the ointment with high percentage emulsifying wax. However the oil phase (liquid paraffin) is not enough for the salicylid acid to diffuse through the membrane. Hence amount of acetylsalicylid acid in the distilled water should be low. 

     Precaution steps that needed to be taken during the experiment are method of ointment preparation. All the bases must be melted before using levigation technique with acetylsalicylid acid. To ensure that ointment are in homogenous state. Therefore drug will evenly distribute in the bases. Next, ensure that surrounding of dialysis bag not contaminated with ointment during the filling of ointment into the dialysis bag. Because the rate of diffusion will be affected if there are some contaminated on dialysis bag. Lastly, ensure that the solution of the beaker does not contain any solution than distilled water.

4. 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?

           The ingredients used in the preparation of the ointment are acetylsalicylic acid, emulsifying wax, white soft paraffin and liquid paraffin. The ingredients for Emulsifying Wax are cetearyl Alcohol, Polysorbate 60, PEG-150 Stearate, and Steareth-20. It mirrors the properties of cetyl alcohol while promoting the thickening features of stearyl alcohol.  The functions of emulsifying wax are thickening the liquid and binding the oil and water-based elements together.

           Acetylsalicylic acid is an active ingredient of this ointment and is also known as aspirin. It is often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication.

          The white soft paraffin works as a moisturiser by providing a layer of oil on the surface of the skin to prevent water evaporating from the skin surface. The function of liquid paraffin is providing an emollient film which reduces water loss from the outermost layer of the skin to the environment. It acts as an emollient.

          To ensure a higher rate of acetylsalicylic acid released from the ointment, the ointment should not harder and should be easily spread on the skin. The penetration rate of the acetylsalicylic acid from the ointment to the skin will be slower if the ointment is too hard. When the amount of emulsifying wax is too large, it makes the ointment harder while when the amount of liquid paraffin is larger, it makes the ointment too liquid. An ideal ointment should have good spreadable, soft and greasy properties. Therefore, the portion of emulsifying wax should be lower and portion of liquid paraffin should be higher. Then, the ointment can be spread readily on the skin and acetylsalicylic acid can penetrate the skin to produce effective therapeutic effect. A well-spreadable property can also help in increasing the exposing surface area of ointment containing drug on the skin to increase drug’s effectiveness.

Conclusion

Different formulation of ointment will affect the physical characteristics of ointment and the rate of release of drug from the formulation. Thus, the components of the formulation must be in suitable proportion to produce a drug which has desired therapeutic effect.

References

http://www.egopharm.com/skin-blog/ingredient-introduction-liquid-paraffin/

http://www.wisegeek.com/what-is-emulsifying-wax.htm

http://en.wikipedia.org/wiki/Ultraviolet%E2%80%93visible_spectroscopy

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