1. To study the influence of ointment composition towards the physical properties of the ointment.
2. To study the rate of drug release from the ointment formulation.
Introduction:
Ointments are semisolid preparations for application to the skin and usually contain a medicament. Ointments are used topically for several purposes. For example, as protectants, antiseptics, emollients, antipruritics, kerotolytics and astringents. The medicament may be in solution, suspension or emulsified in the base. Ointment vehicles serve as protective and emollients for the skin. They usually exhibit plastic flow characteristics and hence when ointment is applied there are a definite yield value, the resistance to flow however drops as the application to the skin is continued. Ointments in the form of semisolid emulsions are also referred to as cream. Ointments and creams containing large proportions of insoluble powders are referred to as pastes.
In the case of a protective ointment, it serves to protect the skin against moisture, air, sun rays and other external factors. It is necessary that the ointment neither penetrates the human skin barriers nor facilitates the absorption of substances through this barrier. An antiseptic ointment is used to destroy or inhibit the growth of bacteria. Frequently bacterial infections are deeply seated, a base which has the capacity to either penetrate or dissolve and release the medication effectively is therefore desired. Ointments used for their emollient effect should be easy to apply, non-greasy and effectively penetrate the skin.
Apparatus:
Weighing balance
|
2 threads
|
Weighing boat
|
1 glass rod
|
100ml beaker
|
Water-bath
|
Heater
|
1 set of pipette (5 ml) and pipette –bulb
|
1 set of slap and spatula
|
1 plastic cuvette
|
1 set of mortar and pestle
|
Spectrophotometer UV/Vis
|
1 dialysis beg (10cm)
|
Materials:
Emulsifying Wax
White soft paraffin
Liquid Paraffin
Acetylsalicylic acid
Distilled-water
Procedures:
1. Emulsifying ointment (50 g) with the formula below was prepared:
3. Acetylsalicylic acid powder (1.5g) was incorporated into the 30 g
ointment formed with the levigation technique (Acetylsalicylic acid powder was
triturated with the pestle and mortar).
4. Acetylsalicylic acid ointment was inserted into the dialysis bag
and two ends of the bed were tied properly as shown in the figure below:
5. The bed was placed into the beaker (250 ml) which contain distilled
water (100 ml) which had been heated to 37°C.
6. A aliquot sample (3-4 ml) was pipetted at the interval 5 minutes
and the release of the Acetylsalicylic acid from the ointment base was
determined by the spectrophotometer UV-visible. The distilled water was stirred
with the glass rod before sampling.
Results :
Observation on texture, spreadibility, colour, and hardness :
Emulsifying ointment 3 :
Discussion :
1.
Compare the physical appearance of
ointment that are formed and discuss.
All these four ointments have the same amount of soft paraffin but
different composition of emulsifying wax and liquid paraffin. These ointments
have oily and greasy texture because they are emulsifying ointments which only
composed of soft paraffin, liquid paraffin and emulsifying wax as the
ingredients. Liquid paraffin will give effective smooth ointments. Ointment 4
gives yellowish colour as it is made up of a small amount of emulsifying wax
and large amount of liquid paraffin compared to the others three ointment which
show white colour.
2.
Plot graph of UV absorption
against time and give explanation.
Inside the distilled water, the
concentration of the drug represents the amount of drug that absorbed into the
blood circulation in our human body. It indicates the bioavailability of the
drug while the dialysis bag shows the absorption of drug across the membrane
into the skin layer.
In this case, amount of drug that crossed the
membrane shows the UV absorption is proportionally to the time throughout the
experiment. UV absorption is proportional to the release time of
acetylsalicylic acid from the tube. The gradient of the graph shows the rate of
release of acetylsalicylic acid from the membrane.
Initially, the temperature is
maintained at 37°C and the water is hypotonic to the tube content. Thus, the
content (acetylsalicylic acid) tends to diffuse out from the tube to the
hypotonic solution. The duration of time is proportional to the concentration
of the salicylic acid in the distilled water. 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 into and out of the tube was achieved. At
this time, the gradient of the graph reduced.
However, the graph does not increase
consistently due to many errors. Firstly, the tube may not be tied tightly
enough or maybe the presence of leakage on the membrane and therefore could not
withstand the stirring. The concentration of acetylsalicylic acid may not be
consistent if the distilled water in the beaker was not stirred uniformly.
Besides, it was important to keep the constant temperature of the water bath.
In addition to that, 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.
3. Compare and discuss the effect of
an ointment formulation with different composition on the release of drug.
The presence of low emulsifying wax causes the matrix not fine enough to
trap liquid paraffin and soft paraffin. Incomplete matrix causes the
emulsifying ointment formed to be unstable and hence it cannot disperse evenly.
As a result, this leads to the hydrophilic ointment to diffuse into the
distilled water through the membrane. High amount of emulsifying wax and low
quantity of liquid paraffin will cause the formulation to become harder. The
matrix formed is very solid and has less liquid. Hydrophilic aspirin may be
able to disperse evenly in the ointment that is emulsified by the emulsifying
agents (emulsifying wax) and the oil phase (liquid paraffin and soft paraffin)
is not enough for the aspirin to diffuse through the membrane. Thus the
concentration of aspirin in the distilled water is low. The uneven ratio causes
it to be trapped in the ointment with the slow release rate.
4. What is
the function of each ingredient used in the preparation of the ointment? How
does the use of different amounts of emulsifying wax and liquid paraffin used
influence the physical characteristic of an ointment formulation and the rate
of drug release from it?
There are some ingredients that
used in this experiment in order to produce the ointment. For example,
emulsifying wax is one of the important ingredients. It is used to stiffen the
ointment and provide hardness to the ointment. Besides, white soft paraffin is
also another ingredient. It is a greasy moisturizer and provides moisturizing
effect on the surface to prevent water loss from the surface. It is added into
the ointment so that the ointment can soften, hydrate and protect the skin and
soothe any irritation, especially in patients with dry skin conditions.
Liquid paraffin also acts as an emollient which soothes, smoothes and hydrates
the skin. Liquid paraffin makes the ointment less viscous.
Different amount of emulsifying agent and
liquid paraffin will affect the physical characteristics of the ointment. For
example, the higher the amount of emulsifying wax and the lower the amount of
liquid paraffin used, the stiffer and the less greasy the ointment. The higher
amount of liquid paraffin will also cause the ointment to be less viscous. When
the ointment contains a higher amount of emulsifying wax and low amount of
liquid paraffin, the rate of drug release will also decrease.
Appendix :
(preparation of the ointment)
(materials started to melt)
(ointment)
(incorporation of the acetylsalicylic acid into the ointment by levigation technique)
(filling the ointment into a dialysis bag)
(beaker is placed into the water bath 37 degree celcius)
(reading was taken from the UV-visible spectrometer)
Conclusion
:
From the experiment,
the higher the amount of emulsifying wax, the ointment will be more hard. This
is due to different compositions of ointment formulation will affect the rate
of drug release. As the high proportion of liquid paraffin will make the
ointment easy to be applied on skin though it will become more greasy and has
low rate of drug release, so, the balance between the amount of emulsifying wax
and liquid paraffin in the ointment is important to achieve an ideal ointment
without compromising the rate of drug release.
References :
1. H. C. Ansel, N. G. Popovich
and L. V. Allen, Jr. 2005. Pharmaceutical
Dosage Forms and DrugDelivery Systems, 8th ed., Williams and Wilkins, Baltimore
2. Aulton, M.E. 2002.
Pharmaceutics: The science of dosage form design. Edinburgh: Churchill
Livingstone.
3. Florence,A.T. & Attwood,
D. 1998. Physico-chemical principles of pharmacy. 3rd Ed. New York: Macmillan.
4. Jelvehgari, Mitra,
Montazam, Hassan. 2011. Evaluation of mechanical and rheological properties of
metronidazole gel as local delivery system. Archives of Pharmacal Research.
0253-6269
Appendix :
(preparation of the ointment)
(materials started to melt)
(ointment)
(incorporation of the acetylsalicylic acid into the ointment by levigation technique)
(filling the ointment into a dialysis bag)
(beaker is placed into the water bath 37 degree celcius)
(reading was taken from the UV-visible spectrometer)
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