Experiment 4: The effects of
differences characteristic of active ingredient in formulation of ointment.
Objectives:
1) To study the effects of difference amount of emulsifying wax, white soft paraffin and liquid paraffin used in the formulation of ointment.
2) To describe and elaborate the texture, clarity and colour of ointment that was formed
INTRODUCTION
Objectives:
1) To study the effects of difference amount of emulsifying wax, white soft paraffin and liquid paraffin used in the formulation of ointment.
2) To describe and elaborate the texture, clarity and colour of ointment that was formed
INTRODUCTION
Ointment
formulation is a semi-solid dosage forms that is suitable for application on
the skin and for external use only. 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. A good ointment must have an
interesting texture, easy to spread on the skin and release the active ingredient.
Ointments are formulated using hydrophobic, hydrophilic, or water-emulsifying
bases to provide preparations that are immiscible, miscible, or emulsifiable
with skin secretion. Ointment bases are intended to soften but not melt when
applied to the skin.
The
purpose of an ointment bases include as a vehicle from which the drug may be
absorbed by the skin and as a protective layer or emollient for the skin. Different
composition of base will greatly affect the pharmacologic effect of a
particular drug. This includes stability, penetrability, solvent property,
approximately neutral with regard to pH, and ease of application and removal.
Therefore in pharmaceutical aspects, choice of bases should be made carefully
to obtain optimum drug distribution.
The
purpose of the laboratory is studying the effects of different ointment
composition on physical characteristics, ointment formed and the rate of drug
release from it.
Apparatus: Weighing balance, 1 weighing boat, 100mL
beaker, heater, I set of slap and spatula, 1 set of mortar and pestle, 1 dialysis
bag (10cm), thread, glass rod, water-bath, pipette and pipette bulb,
Spectrophotometer UV.
Materials: Emulsifying wax, White soft paraffin, Liquid
paraffin, Acetylsalicylic acid, distilled water.
PROCEDURE
1.
50g of emulsifying ointment was prepared through formulation as following:
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.
5g of ointment was taken from the total of 50g and was placed into weighing
boat and labelled. The texture, clarity and colour of ointment was observed and
compared.
3.
1.5g of Acetylsalicyclic acid was incorporated into 30g of made ointment by
using levigation. (Acetylsalicyclic acid powder was crushed into finer
particles using mortar and pestle if required.)
4.
The Acetylsalicyclic acid ointment was filled into dialysis bag. Both ends of
the bag were tied.
5.
The dialysis bag was placed into 100ml beaker which contains 50ml of saline
water and heated in water-bath to 370C.
6.
One aliquot sample (3-4ml) was pipetted at an interval of 5 minutes. Rate of
release of Acetylsalicyclic acid from the ointment tube was determined by using
UV-visible spectrometer. The saline water was stirred by glass rod before the
sample was taken.
RESULT AND DISCUSSION
1. Compare and discuss the physical properties of ointment prepared.
Throughout the
experiment, we prepare four 50g Emulsifying Ointments of different composition
ratio. Emulsifying Ointment I consists of 21g of Emulsifying Wax, 25g of White
Soft Paraffin and 4g of Liquid Paraffin; Emulsifying Ointment II consists of
17g of Emulsifying Wax, 25g of White Soft Paraffin and 8g of Liquid Paraffin;
Emulsifying Ointment III consists of 13g of Emulsifying Wax, 25g of White Soft
Paraffin and 12g of Liquid Paraffin; Emulsifying Ointment IV consists of 9g of
Emulsifying Wax, 25g of White Soft Paraffin and 16g of Liquid Paraffin.
Each of the ointments
prepared has different physical appearance. In terms of spreadability,
Emulsifying Ointment IV is the most spreadable, followed by Emulsifying
Ointment III, and Emulsifying Ointment II. As compared, Emulsifying Ointment I
is the least spreadable among all.
In the aspect of
greasiness, Emulsifying Ointment IV is the greasiest, followed by Emulsifying
Ointment III, and Emulsifying Ointment II. Emulsifying Ointment I is the least
greasy.
In terms of hardness,
Emulsifying Ointment I is the hardest, followed by Emulsifying Ointment II, and
Emulsifying Ointment III. Emulsifying Ointment IV is the softest.
Based on these
comparisons, we found that the physical properties of Emulsifying Wax are tends
to be more solidified in semisolid preparation. We can know this through the
observation on its hardness, greasiness and spreadability. It tends to decrease
in greasiness and spreadability while increasing in hardness.
On the other hand, Paraffin
Oil tends to be more liquidified in semisolid preparation. Based on its
physical properties, Paraffin Oil is increase its greasiness and spreadability
while decreasing in hardness.
Therefore, to prepare an ideal
ointment, we must balance the composition of Emulsifying Wax and Paraffin Oil so
that the ointment produced will not be neither too hard nor too soft.
2. Plot a graph of UV absorbtion against time. Explain
This graph shows the
reading obtained from the UV spectrometer. The UV spectrometer measures the
releasing of acetylsalicylic acid from the ointment in the dialysis bag
immersed in the 100 ml 37°C distilled water. The mass of emulsifying wax is 9
g, white soft paraffin is 25 g, and liquid paraffin is 16 g. Overall, the graph
shows the gradual increasing in the absorption of UV with a large increase at
the initial. Initially, at the first 10 minutes, the UV absorption value surge
up follow by gradual increasing of the UV absorption value until 30 minutes.
The great increase in the UV absorption value at the first 10 minutes is due to
the great concentration difference between content in dialysis tube and the
distilled water. The content of in the dialysis bag is hypertonic to the
distilled water. So, large amount of ointment with acetylsalicylic acid
diffuses to the distilled water with high concentration gradient different. The
amount of ointment diffuse is proportional to the acetylsalicylic acid. The
high value of UV absorption may due to the presence of residual at both end of
the dialysis bag, left during the insertion of ointment into the dialysis bag.
So when the dialysis bag is immersed in the distilled water, the residual will
dissolve in the water. This makes there are content of acetylsalicylic acid
that are not from the diffusion through the dialysis bag. After the residual at
both end of dialysis bag has dissolved all, the acetylsalicylic acid diffused
out only through the pore of dialysis bag, so the readings between 10 to 20
minutes show regular increase. A sudden large increase in the UV absorption
does not occur after 10 minutes as the concentration gradient across the
dialysis bag decrease, the amount of acetylsalicylic acid in the distilled
water increases with time. The gradual increase in the UV absorption indicates
the gradual release of acetylsalicylic acid from the dialysis bag. The
concentration of content in distilled water gradually equals the concentration
of the content in dialysis bag. This will result in the reduced increase in the
UV absorption when time passes by.
If the experiment is continued beyond 30 minutes, it may result in a
straight line graph as the concentration of acetylsalicylic acid in the
distilled water equals to the concentration of acetylsalicylic acid at the
dialysis bag. The content in dialysis bag is isotonic to the distilled water
content concentration.
Some of the precautious steps can be taken during conducting the experiment are
to avoid over stirring the distilled water as this might break the dialysis bag
and result a large amount release of the ointment from it. Besides, the
residual that retained at both end of the dialysis bag should be removed before
immersing the dialysis bag in the distilled water to ensure accuracy of the
result. The rope should tie both end of the dialysis bag tightly to prevent
leakage of the ointment. The cuvette should be cleaned for the fingerprint
around the surface of it so that the measurement is correct. The distilled
water in the beaker should cover the whole dialysis bag to ensure consistent
diffusion.
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
|
0.063
|
0.121
|
0.212
|
0.224
|
0.235
|
0.294
|
0.331
|
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 materials used in this ointment
preparation? How the different ratio of emulsifying wax and liquid paraffin
used influence the physical characteristics of an ointment formulation and the
rate of drug release from the ointment preparation.
Liquid paraffin is used as a
blending base and as an emollient. It also helps to increase the
spreadibility of the ointment to be easier to be applied on the skin. Besides,
it is usually formulated with white or yellow soft paraffin to achieve the
required viscosity for application to the required site.
White soft paraffin has also give advantage as a skin protectant.
It is a hydrophobic compound that repels water and retaining the moisture of
the skin. Since white soft paraffin is a rich emollient, it has the ability to
penetrate deeper into the skin than other lotions or compounds. Its
contribution to the thickness of the compound forms a barrier on the skin that
further prevents additional water from escaping the top layers of the skin.
Emulsifying
wax has emulsifying properties. It has the function of increasing the viscosity
of oil-in-water emulsions, thereby improving their stability, and also gives
emollient effect when added to paraffin ointment. High ratio of emulsifying wax
in the ointment will increase the rate of release of drug as it act as
surfactant that decrease the surface tension and hence increase absorption. It
will assist in improving the consistency and texture of final product without
leaving a greasy film on the outer skin after application. It also controls the
rheological properties of the system by their interaction with water and other
excipients in the external phase. The unique characteristics of emulsifying wax
give certain solidity to emulsified solutions, enables product to easily spread
and glide on the skin. It is also used as an emulsifier, which enables the
blend of oil and water to prevent bleeding and phase separation.
Liquid paraffin is a viscosity
builder. Thus, the higher the amount of liquid paraffin used, the more viscous
of an ointment and the slower the drugs or active ingredients being released. High contain of
liquid paraffin will cause the ointment become greasy. Liquid paraffin is usually used in combination with white
soft paraffin. An appropriate combination of liquid paraffin with white soft
paraffin will give an ointment with desirable properties. Emulsifying
wax is a penetration enhancer. Thus, the higher the
amount of emulsifying wax added, the faster the drug release rates. Besides, an emulsifying wax is to soften and give thickness to
ointments. Hence, a high content of emulsifying wax cause the ointment become hard.
In conclusion, the standard ratio of emulsifying wax: white soft paraffin:
liquid paraffin is 3:5:2. The ratio of emulsifying wax must be higher than
liquid paraffin as emulsifying wax acts to release drug rapidly from the
ointment preparation. Liquid paraffin is used to increase the spredibility of
the ointment.
CONCLUSION
Different compositions of bases for ointment formulation affect the physical characteristics and its release rate of drug.
REFERENCES
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3. Pharmaceutics, The Science of Dosage Form Design, Michael Aulton, 3rd Edition
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