Experiment 1- Ointment

INTRODUCTION

Ointment is a semi-solid containing active ingredient and other excipient. The active ingredient may be one or more. It is intended to be used topically onto our skin and provide an emollient effect. It is advisable to consult a patient to use the ointment preparation after bath and during the skin still wet. This is because the ointment will form a thin layer coating the skin surface preventing water loss from skin. A good ointment preparation must have a good texture, easily to applied and not too greasy.

OBJECTIVE

1. To investigate physical characteristics by using different composition of ointments.
2. To find out rate of drug being released by using different composition of ointments.

APPARATUS & MATERIALS

1. Weighing balance
2. Heater
3. Spectrometer
4. 100ml Beaker
5. Weighing boat
6. Pestle and mortar
7. Glass slap
8. Glass rod
9. Spatula
10. 10cm Dialysis beg
11. 5ml Pipette and bulb
12. Plastic cuvette
13. Thread
14. Emulsifying wax
15. White soft paraffin
16. Liquid paraffin
17. 5g Acetylsalicylic acid
18. Distilled water

PROCEDURES

1. Emulsifying Ointment (50 g) was prepared following this formula:

Emulsifying ointment	Group	Ingredients			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. Some of the ointment formed (5 g) was taken and placed into a weighing boat and was labeled. The texture, clarity and color of the ointment formed was described and compared.
3. The acetylsalicylic acid powder was incorporated (1.5 g) into 30 g ointment which has been prepared using the levigation technique. The acetylsalicylic acid was triturated using the mortar and pestle.
   
4. Fill the acetylsalicylate acid ointment into the dialysis bag and both of the end of the beg were tied tightly, as shown in the figure below:
5. The bag was inserted into a beaker (100 ml) containing distilled water (50 ml) which has been heated to 37⁰C.
6. In the interval of 5 minutes, an aliquot sample (2-5 ml) was pipette and the acetylsalicylic acid released from the ointment base was determined using the UV-visible spectrometer. The distilled water was ensured to be stirred before the sample was taken.

RESULTS

Time (minutes)	UV Absorption
UV Absorption at 300 nm	0	5	10	15	20	25	30
	0.128	0.137	0.162	0.173	0.255	0.476	0.522

 

DISCUSSION

1. Compare the physical characteristic for the ointments and explain.

Experiment	Material (g)			Texture of ointment			Clarity
	Emulsifying Wax	White soft paraffin	Liquid paraffin	Spreadibility	Greasiness	Hardness
I.	21	25	4	Difficult	Least greasy	Hardest	Turbid
II.	17	25	8	Little difficult	Little greasy	Less harder	Turbid
III.	13	25	12	Less difficult	More greasy	Little soft	Turbid
IV.	9	25	16	Easy	Most greasy	Softest	Turbid

 

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

 

The UV spectrometer measures the releasing of acetylsalicylic acid from the ointment in the dialysis bag to the distilled water. The release of the drugs from the ointment involved the diffusion mechanism. The water is set to 37 ⁰C to mimic the temperature of human body as ointment will be applied to human skin. Meanwhile, the dialysis bag represents the skin membrane.

The amount of drug absorbed into the blood circulation is represented by the concentrations of the drug in the distilled water. The UV absorption represents the concentration of the drug that crosses the membrane and reaches into  the distilled water. In theory, the UV absorption is proportional to the time of the release of acetylsalicyclic acid across the membrane to distilled water. The gradient of the graph shows the rate of drug release across the membrane of dialysis bag.

The graph shows that as the time increases, the concentration of the acetylsalicyclic acid in the distilled water is increasing. Along the time until a particular point, the gradient of the graph decreases thus the releasing rate is reduced. Along the progression of the experiment, the concentration of salicyclic acid in the dialysis bag and the distilled water become isotonic because the salicyclic acid keeps moving into the distilled water and equilibrium occurs.

This will result in the reduced gradient of the graph when time passes by. If the experiment is continued beyond 60 minutes, it may result in a straight line graph as the acetylsalicyclic acid diffuses into and out of the membrane of dialysis bag in an equilibrium state. At the late stage, the releasing rate increases. This may be contributed by the experimental error such as leakage of the drug whereby the thread is not tight tightly enough or  the distilled water is stirred too vigorously.

 

3. Plot a graph of UV Absorption against time for ointment formulations of different composition. Compare and discuss the results obtained.

Time (min)	UV Adsorption
	0	5	10	15	20	25	30
UV absorption at 300nm	0.128	0.137	0.162	0.173	0.255	0.476	0.522

 

Time (min)		Average UV absorption at 300nm (x ± SD)
Emulsifying ointment		0	5	10	15	20	25	30
	I	0.049	0.060	0.370	0.280	0.050	0.315	0.031
		0.075	0.093	0.257	0.301	0.334	0.428	0.443
	AVG	0.062	0.0765	0.3135	0.2905	0.1920	0.743	0.237
	SD	0.0183	0.0233	0.0798	0.01485	0.2008	0.5314	0.2913
	II	0.202	0.205	0.194	0.239	0.288	0.318	0.337
		0.360	0.390	0.413	0.415	0.498	0.525	0.544
	AVG	0.281	0.2975	0.3035	0.327	0.393	0.4215	0.4405
	SD	0.1117	0.1308	0.1549	0.1245	0.1485	0.1464	0.1464
	III	0.070	0.088	0.076	0.166	0.153	0.087	0.163
		0.004	0.024	0.034	0.081	0.078	0.089	0.127
	AVG	0.037	0.056	0.055	0.124	0.116	0.088	0.145
	SD	0.0467	0.0453	0.297	0.0601	0.0530	0.0014	0.0255
	IV	0.128	0.137	0.162	0.173	0.255	0.476	0.522
		0.114	0.335	0.329	0.350	0.192	0.281	0.655
	AVG	0.121	0.236	0.246	0.262	0.224	0.379	0.589
	SD	0.009	0.140	0.118	0.125	0.045	0.138	0.094

 

The ideal ratio of amount Emulsifying Wax, White Soft Paraffin and Liquid Paraffin in the preparation ointment is 30 : 50 : 20. Theoretically, an ointment that contains the highest amount of emulsifying wax and lowest amount of liquid paraffin will take longer time for the acetylsalicylic acid to penetrate from the dialysis membrane. This results in the lowest reading of UV absorption by the acetylsalicylic acid. This can be explained by the theory stated that when there is a low amount of emulsifying wax,  the acetylsalicylic acid cannot disperse well in the ointment. As we increase the amount liquid paraffin in the formulation, greater amount of acetylsalicylic acid is able to penetrate the dialysis membrane at a faster rate. This is due to the role of liquid paraffin in the formulation that improves hydration, thus increase the effectiveness of the absorption of the ointment at the percutaneous membrane.

In the experiment conducted, four formulations were prepared. The formulations possessed different amount of emulsifying wax and liquid paraffin. Results obtained have shown that Formulation 1 which contained the least amount of liquid paraffin resulted in the lowest UV absorption value. Formulation 3 showed higher UV absorption than Formulation 1. This is followed by Formulation 4 and Formulation 2 with the greatest amount of UV absorption. As the amount of emulsifying wax reduces, with an increase in the amount of liquid paraffin, the UV absorption of acetylsalicylic acid should increase. From the results obtained, there is a slight inaccuracy because supposedly Formulation 2 shows lower UV absorption than Formulation 3 and Formulation 4. This inaccuracy might be due to several possible errors done during the experiment.

The possible errors may be due to the inaccurate measurement of amount of ingredients used in the formulation prepared. This will affect the permeation rate of Acetylsalicylic acid and the UV absorption. Secondly, the absorption of UV may get affected by the inaccurate or different amount of ointment filled in the dialysis bag. Besides, the presence of contaminants on the dialysis bag could also contribute to the inconsistent results. Moreover, the spillage of the drug from the dialysis could be one of the errors that could alter the results.

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?

Emulsifying wax Is a type of anionic emulsifying agent which act as needed to mix two phases, (oil-soluble and water-soluble)phases and forms a layer known as interface. It helps in decreasing the interfacial surface tension to enable the drug particles to be distributed evenly in the ointment which prevents  sedimentation from occurring.

White soft paraffin and liquid paraffin are hydrocarbon base. White soft paraffin also known as white petroleum  jelly. It act as moisturizer and emollient by providing a layer of oil on the surface of the skin to prevent water  evaporating  from the skin surface. It increases the greasiness of the ointment and is able to penetrate through the hydrophobic layer of the skin more readily. It also serve as stabilizer. Liquid paraffin is used to reduce the viscosity of the base so that the emollient will easily expelled from its container. Combination of white soft paraffin and liquid paraffin is to achieve viscosity.

Acetylsalicylic  acid is the active ingredient in this ointment preparation and play a major role as the active ingredient. It also known as aspirin that give therapeutic effect by given antipyretic, anti-inflammatory and analgesic effect by enzyme inhibitor. The grainy of texture of dissolved aspirin also serves to exfoliate the skin.

The composition of each bases in ointment very important to determine characteristic of ointment produce. Emulsifying wax will give hardness to the ointment due to its high melting point. Then, liquid paraffin can give softness to the ointment if large amount added. Lower portion of emulsifying wax and large portion of liquid paraffin will increase spreadibility and greasiness and enhance the release of drug and help in penetrate the skin lipid bilayer readily.

CONCLUSION

The proportion of emulsifying wax and liquid paraffin should be in balance in order to produce an ointment with desired hardness. This can ensure that the active ingredients can be released at an optimum rate and increase the bioavailability.