Title
Experiment 1: Evaluation of Effects Different
Ingredients towards the Ointment Formulation
Objective
To determine the influence of ointment composition
towards the physical properties of the ointment and the rate of drug release
from the ointment formulation.
Introduction
Ointment formulation is a form of
semi-solid that suitable to be used as skin application. Ointment is a
preparation that contains one or more active ingredient disperse homogenously.
For ointment preparation, disperse phase is water, while continuous phase is
oil, so it is a water-in-oil system. A good ointment should have an interesting texture, easy to apply and able
to release its drug content after application to targeted sites.
In general for ointment preparation,
drug or active ingredient is incorporated into oily medium of continuous phase.
Ointment is normally applied topically to dry area of the skin for emollient
effect. Ointment gives a protective layer to prevent dehydration of skin.
Hence, the objective of this experiment
is to determine the effect of different composition included on the physical
properties of ointment and its preparation process, as well as the rate of
release of active ingredient.
Apparatus
1. Weighing
machine
2. Weighing
boat x 1
3. 100mL
beaker x 1
4. Heater
5. Set
of slap and spatula
6. Set
of mortar and pestle
7. Dialysis
bag (10cm) x 1
8. Short
strings x 2
9. Glass
rod
10. Water
bath
11. Set
of pipette (5cm) and pipette bulb
12. Cuvette
plastic x 1
13. Ultraviolet
spectrophotometer
Material
1. Emulsifying
wax
2. White
soft paraffin
3. Liquid
paraffin
4. Acetylsalicylic
acid
5. Distilled
water
Method
1. Emulsifying
ointment (50g) is prepared by using following formula :
2. Small
amount of ointment formed (5g) is took and put into a weighing boat and
labelled. The ointment formed is compared its texture, clarity and colour.
3. Acetylsalicylic
acid powder (1.5g) is incorporated into 10g of prepared ointment using
levigation method. (Acetylsalicylic acid powder is crushed into finer using
mortar and pestle if needed). The acetylsalicylic
acid powder is inserted into dialysis bag. The both end of dialysis bag is made
sure tighten properly with short strings, as shown in the figure below.
4. The
bag is inserted into a 100mL beaker contained 50mL distilled water that has
been heated to 37 degree Celsius.
5. At
the time interval of 5 minutes, 1 aliquot sample (3-4mL) of sample is pipetted
and the release of acetylsalicylic acid from ointment base is determined using
visible UV spectrometer. Distilled water is made sure stirred with a glass rod
before sample is taken.
Discussion
1. Comparison
for the physical properties of different ointment formed and comments.
Ointment
Physical
appearence
|
I
|
II
|
III
|
IV
|
|
1.
Texture
a)
Spreadibility
b)
Greasiness
c)
Hardness
|
Very
difficult
A
bit greasy
Very
hard
|
Difficult
Less
greasy
Hard
|
Easy
Greasy
Soft
|
Very
easy
Very
greasy
Very
soft
|
|
2.
Turbidity
|
Very
turbid
|
Turbid
|
Less
turbid
|
Less
turbid
|
|
3.
Colour
|
White
|
White
|
White
|
White
|
|
In this experiment, the difference of the ointments
made by different groups was the amount proportion of emulsifying wax and
liquid paraffin used in the preparation. In this case, the amount of white soft
paraffin used was same for every group.
Based
on the observation on the ointments formed from every group, comparison can be
made based on the aspects of texture, clarity and the colour of the ointments.
For the texture, ability to spread (spreadability), greasiness and hardness are
taken into account for comparison. The spreadability and hardness of ointment
was dependent on the amount of emulsifying wax used. Ointment I had the highest
amount of emulsifying wax (21g), thus the ointment was the most difficult to
spread and hardest compared to other 4 ointments. However, ointment IV was the
softest and easiest to spread due to the least amount of emulsifying wax used
(9g). In addition, ointment III was easier to spread and softer compared to
ointment II as it contained less emulsifying wax. Apart from the contribution
of emulsifying wax, liquid paraffin also will affect the hardness of ointment.
The higher the content of liquid paraffin used, the softer the ointment formed.
Besides, the presence of liquid paraffin determines
the greasiness of the ointment. The highest content of liquid paraffin (16g) in
emulsifying ointment IV make it the greasiest ointment compared to ointments I,
II and III. Ointment I was the least greasy due to the lowest amount of liquid
paraffin used (4g).
For the comparison of turbidity, the physical
appearance of emulsifying ointment I was the most turbid and the turbidity
become less and less proceeding to the ointment IV due to the amount of liquid
paraffin used. The higher the content of liquid paraffin used in the ointment, the
lesser the degree of turbidity of ointment. For the
appearance or colour of the ointment, all of the ointments formed were white in
colour because liquid paraffin which is white gave its colour to the ointments.
2. Plot
the graph of UV absorption against time. Give explanation.
Time (min)
|
UV absorption
|
||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
|
UV absorption at 310nm
|
0.00
|
2.00
|
2.40
|
3.30
|
3.60
|
4.00
|
4.50
|
In this experiment, the dialysis bag resembled the
human skin where the absorption of drug occurs when the drug crosses the
membrane into the layers of the skin. The concentration of the drug in the
distilled water detected by the UV spectrophotometer represents the amount of
drug absorbed into the blood circulation and also the bioavailability of the
drug.
UV absorption represents the amount of drug that has
crossed the membrane. The experiment showed that generally the UV absorption is
proportional to the time throughout the experiment duration. By theory, UV
absorption is proportional to the release time of acetylsalicylic acid from the
tube. The gradient of the graph shows the rate of released of acetylsalicylic
acid from the membrane.
The graph showed that in the beginning, the
concentration of the acetylsalicylic acid in the distilled water increased slight
rapidly with time from 0.00 to 5.00. The release rate will continue until a
saturation point is achieved. As the time increased until a particular time,
the releasing rate will reduce (gradient of the graph decreased). This
situation can be explained from the graph as distilled water had achieved its
saturation point. At the late stage of experiment, the releasing rate decreased
gradually.
At the beginning of the experiment, the distilled
water was kept at 37°C and it was hypotonic to the dialysis bag’s content
consisted of acetylsalicylic acid. Thus, acetylsalicylic acid tended to diffuse
out from the tube to the hypotonic solution (distilled water).
As the time increased, the concentration of salicylic
acid in the distilled water increased. As the experiment proceeded, the
concentration of the acetylsalicylic acid in the tube became isotonic with the
distilled water in the surrounding. This showed that the equilibrium for diffusion
of acetylsalicylic acid in and out of the tube was achieved. At this time, the
gradient of the graph reduced.
The gradient did not show much difference compared
from the starting till the end. When there was situation that gradient did not
decrease or increase consistently maybe due to some errors such as careless
attitude of experimenter didn’t make sure the cleanliness of apparatus. The
concentration of acetylsalicylic acid may not be consistent if the distilled
water in the beaker was not stirred uniformly. Besides, the technique of using
spectrophotometry device also played a vital role in getting accurate results.
The smooth surface of the cuvette should face the source of UV light and the
smooth surface should be cleaned before it was placed into the device.
Handprint when we held it caused the ultraviolet ray cannot pass through
smoothly and affected the result. When we were holding the cuvette, it was not
advisable to hold the smooth surface (where there is a triangle symbol on it).
1. 3.
Plot a graph of UV absorption versus time for ointments that have different
compositions. Compare and discuss the results.
Times(min)
|
UV absorption
|
||||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
|||
Emulsifying Ointment
|
I
|
1
|
0.064
|
0.081
|
0.097
|
0.095
|
0.106
|
0.115
|
0.121
|
5
|
0.000
|
0.032
|
0.047
|
0.045
|
0.052
|
0.074
|
0.084
|
||
II
|
2
|
0.004
|
0.007
|
0.011
|
0.028
|
0.032
|
0.037
|
0.049
|
|
6
|
0.052
|
0.073
|
0.193
|
0.211
|
0.274
|
0.339
|
0.369
|
||
III
|
3
|
0.104
|
0.111
|
0.119
|
0.155
|
0.162
|
0.191
|
0.221
|
|
7
|
0.000
|
0.031
|
0.051
|
0.070
|
0.098
|
0.130
|
0.174
|
||
IV
|
4
|
0.222
|
0.252
|
0.304
|
0.322
|
0.410
|
0.470
|
0.517
|
|
8
|
0.019
|
0.089
|
0.115
|
0.162
|
0.190
|
0.204
|
0.275
|
||
Times(min)
|
UV absorption
|
||||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
|||
Emulsifying Ointment
|
I
|
0.032
±0.045
|
0.057
±0.035
|
0.072
±0.035
|
0.070
±0.035
|
0.079
±0.038
|
0.095
±0.029
|
0.103
±0.026
|
|
II
|
0.028
±0.034
|
0.040
±0.047
|
0.102
±0.093
|
0.120
±0.129
|
0.153
±0.171
|
0.188
±0.214
|
0.209
±0.226
|
||
III
|
0.052
±0.074
|
0.071
±0.057
|
0.085
±0.048
|
0.113
±0.060
|
0.130
±0.045
|
0.161
±0.043
|
0.198
±0.043
|
||
IV
|
0.121
±0.144
|
0.171
±0.115
|
0.210
±0.134
|
0.242
±0.113
|
0.300
±0.156
|
0.337fc
±0.188
|
0.396
±0.171
|
||
Table 1
From the graph, ointment IV showed the greatest
gradient among the 4 slopes. This result that ointment IV had the highest
reading of released acetylsalicylic acid. This was due to the presence of low amount
of emulsifying wax and high proportion of liquid paraffin added that caused the
matrix not fine enough to trap liquid paraffin and soft paraffin. Incomplete
matrix caused the emulsifying ointment formed to be unstable and hence it
cannot disperse evenly. As a result, this leaded to the hydrophilic ointment to
diffuse into the distilled water through the membrane.
Meanwhile, from the graph drawn above, we can know
that ointment I showed the lowest release rate of acetylsalicyclic acid. This
was because ointment I is made up of formulation which contains high amount of
emulsifying wax and low quantity of liquid paraffin. This formulation was much
harder than the other formulations. The matrix formed was very solid and has
less liquid. Hydrophilic aspirin may be able to disperse evenly in the ointment
that was emulsified by the emulsifying agents (emulsifying wax) and the oil
phase (liquid paraffin and soft paraffin) was not enough for the aspirin to
diffuse through the membrane. Thus the concentration of aspirin in the
distilled water was low. The uneven ratio caused it to be trapped in the
ointment with the slow release rate.
There was inaccuracy of result from the graph where
the gradient of for ointment III should be higher than ointment II. However,
the gradient of both graphs were interchanged where ointment II is higher than
ointment III. At the same time, the standard deviation calculated for from the
average reading obtained had very high value for particular reading. This was
because the result for 2 experiments conducted using same material proportion
ended up in different reading which had large difference. The inaccuracy of the
result of our experiment may be due to the inconsistency of stirring of the
distilled water before taking the aliquot sample out at interval of 5 minutes.
The inconsistency of stirring may result in the uneven distribution of the
acetylsalicylic acid. As such, when the aliquot sample was taken, there may be
uneven amount of acetylsalicylic acid being taken for UV spectrophotometer determination.
Other errors include the loss of ointment when transferring the ointment into
the dialysis bag.
As such, several precautions should be taken to reduce
the errors made during the experiment. The distilled water should be stirred
continuously in order to ensure the uniform distribution of acetylsalicylic
acid. Besides, excess ointment should be made to overcome the loss of ointment
while transferring it into the dialysis bag.
Question
1. What
is the function of each material used in the preparation of ointment? How did
the usage of different amount content of Emulsifying Wax and Liquid Paraffin
affect the physical characteristics of a ointment formulation as well as the
rate of release of active ingredients from it?
Emulsifying wax is a emulsifying agent which has the
function to decrease the interfacial surface tension so that drug particles can
be distributed uniformly in the ointment preparation to prevent any
sedimentation happens.
Liquid paraffin acts as a base. Liquid paraffin softens
the ointments formed and decreases the ointment viscosity as well as for
emollient function. Besides, white soft paraffin acts as ointment base. It
increases the greasiness of ointment so that it can penetrate through the skin
hydrophobic lipid bilayer more easily.
The different ratio and proportion of liquid paraffin
and emulsifying wax has direct effect on the preparation. When the proportion
of emulsifying wax decreases while liquid paraffin increases, the ability to
spread and greasiness of ointment increases, meanwhile the hardness decreases.
Hence, the drugs or active ingredients can be released from the formulation and
pass through hydrophobic skin bilayer more readily.
Conclusion
Ointment composition can influence the physical
properties of the ointment and the rate of drug release from it. Ointment which
contains a lower amount of emulsifying wax and a higher amount of liquid
paraffin is softer, less viscous and easy to be spread. Therefore, the rate of
drug release also increases with the decrease in the amount of emulsifying wax
and the increase in the amount of liquid paraffin used.
Reference
1. http://www.pharmlabs.unc.edu/labs/ointments/bases.htm
3. www.drugs.com
› Professionals › Medfacts
Pictures
Emulsifying
wax was melted first on the evaporating dish due to its higher melting point.
The evaporating dish was heated on the magnetic stirrer.
5g
of the acetylsalicylic acid ointment was taken out and put into a weighing boat
to observe the texture of the ointment formed.
The
ointment was incorporated with acetylsalicylic acid powder and was levigated on
a glass slab.
The
cuvette containing the sample was then inserted into the UV spectrometer to
determine the amount of acetylsalicylic acid released from the dialysis bag.
The
reading shown on the UV and visible spectrometers measured the amount of
ultraviolet and visible light transmitted or absorbed by the sample.
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