LECTURER'S NAME: DR NG SHIOW FERN
GROUP B2
AIM :
GROUP B2
AIM :
To study the effects of different ointment composition on the physical
characteristics of ointment formed and the rate of drug released from it.
INTRODUCTION:
Ointments are semisolid preparations for application to the skin or
mucosae. The ointment bases are almost always anhydrous and generally contains
one or more medicaments in suspension or solution. Characteristics of an ideal
ointment are it should be chemically and physically stable, it should be smooth
and free from grittiness, it should melt or soften at body temperature and be
easily applied, the base should be non-irritant and should have no therapeutic
action and the medicament should be finely divided and uniformly distributed
throughout the base. Ointment include in topical medication which is a
medication that is applied to body surfaces such as the skin or mucous
membranes to treat ailments via a large range of classes including but not
limited to creams, foams, gels, lotions, and ointments. Topical medications
differ from many other types of drugs because mishandling them can lead to
certain complications in a patient or administrator of the drug. Ointment is a
type of semi-solid that are suitable for topical application which consist of
one or more active substances mix homogenously. A topical effect, in the
pharmacodynamic sense, may refer to a local, rather than systemic, target for a
medication. However, many topically administered drugs have systemic effects.
APPARATUS:
Weighing balance
|
UV spectrophotometer
|
Weighing boat
|
Plastic Kuvette
|
Glass slab & spatula
|
Pipette
|
Dialysis
|
Heater
|
Mortar & pestle
|
2
Threads
|
100ml beaker
|
Glass rod
|
Water Bath
|
MATERIALS:
Emulsifying wax
|
White soft paraffin
|
Liquid paraffin
|
Acetylsalicylic acid
|
Distilled water
|
PROCEDURE:
1) 50g of
Emulsifying Ointments were prepared by using the following formula:
Emulsifying Ointment
|
Group
|
Ingredients (g)
|
||
Emulsifying
Wax
|
White
Soft Paraffin
|
Total
(g)
|
||
I
|
1, 5
|
21
|
25
|
50
|
II
|
2, 6
|
17
|
25
|
50
|
III
|
3, 7
|
13
|
25
|
50
|
IV
|
4, 8
|
9
|
25
|
50
|
2) 5g of ointment
formed was weighed. The ointment was put in the weighing boat and labeled. The
texture, clarity and the colour of the ointment formed were discussed and
compared.
3) 1.5 g of
Acetylsalicylic acid powder was incorporated into 30 g of ointment that was
prepared by using levigation technique.
4) Acetylsalicylic
acid ointment was weighed and filled into the dialysis beg. Both end of the bag
were tied properly as shown below.
5) The dialysis beg was put into a 100mL beaker with 50mL of distilled
water which has been heated at 370C.
6) With the interval of each 5 minutes, 3-4mL of the
distilled water was pipetted out. The release of acetylsalicylic acid from the
ointment was determined by using UV-visible spectrometer. Distilled water was
stirred before taking the sample.
RESULTS
Table 1: Texture, clarity and the color of the ointments
Emulsifying Ointment
|
Texture
|
Clarity
|
Colour
|
I
|
Lowest
spreadability, least greasy, hardest
|
Clear
|
Milky White
|
II
|
Low spreadability,
less greasy, soft
|
Cloudy
|
Milky White
|
III
|
Spreadable, greasy
and softer
|
Slightly turbid
|
Milky White
|
IV
|
Most spreadable,
greasiest and softest
|
Turbid
|
Milky White
|
Table 2: UV absorption of
Ointment 2
Time
(min)
|
UV Absorption
|
||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
|
UV
Absorption at 310nm
|
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
|
|
Average
|
0.281
|
0.595
|
0.304
|
0.327
|
0.393
|
0.422
|
0.441
|
DISCUSSION:
1. Compare
the physical appearance of the ointments formed and explain.
All different ointment formed of 50g has different amount of emulsifying
wax and liquid paraffin but only white soft paraffin has fixed amount of 25g.
Different amount of emulsifying wax and liquid paraffin gives different
characteristics on the greasiness and hardness. The higher the amount of
emulsifying wax, the higher their hardness. The higher the amount of liquid
paraffin, the higher the greasiness and softness. For Group 1 ointment that has
the highest emulsifying wax in their ointment which is 21g and only 4g of
liquid paraffin, the ointment formed has the hardest and least greasiness
properties. For Group 4 ointment that has the lowest emulsifying wax which is
9g but highest amount of liquid paraffin which is 16g, the ointment formed has
the softest and most greasiness properties. Ointment of Group 2 has more
hardness but lower greasiness than Group 3 as Group 3 has slightly higher
amount of liquid paraffin, which is 12g instead of 8g for Group 2 and slightly
lower amount of emulsifying wax, which is 13g instead of 17g for Group 2. For
colour of the ointment, there is not big differences for each ointment
observed, which is milky white.
2. Plot a
graph of UV absorption against time.
3. Plot
graph of UV absorption against time for different ointments with different
composition. Compare and discuss the result.
Time (min)
|
UV absorption at 300 nm
|
||||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
|||
I
|
1
|
0.049
|
0.060
|
0.370
|
0.280
|
0.050
|
0.315
|
0.031
|
|
5
|
0.075
|
0.093
|
0.257
|
0.301
|
0.334
|
0.428
|
0.443
|
||
II
|
2
|
0.202
|
0.205
|
0.194
|
0.239
|
0.288
|
0.318
|
0.337
|
|
6
|
0.360
|
0.390
|
0.413
|
0.415
|
0.498
|
0.525
|
0.544
|
||
III
|
3
|
0.070
|
0.088
|
0.076
|
0.166
|
0.153
|
0.087
|
0.163
|
|
7
|
0.004
|
0.024
|
0.034
|
0.081
|
0.078
|
0.089
|
0.127
|
||
IV
|
4
|
0.128
|
0.137
|
0.162
|
0.173
|
0.255
|
0.476
|
0.522
|
|
8
|
0.114
|
0.335
|
0.329
|
0.350
|
0.192
|
0.281
|
0.655
|
||
Time(min)
|
UV Absorption Average at 300 nm (Mean ± SD)
|
||||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
|||
|
I
|
0.0620
±
0.01838
|
0.0765
±
0.02333
|
0.3135
±
0.07990
|
0.2905
±
0.01485
|
0.1920
±
0.20082
|
0.3715
±
0.07990
|
0.2370
±
0.29133
|
|
II
|
0.2810
±
0.11172
|
0.2975
±
0.13081
|
0.3035
±
0.15486
|
0.3270
±
0.12445
|
0.3930
±
0.14849
|
0.4215
±
0.14637
|
0.4405
±
0.14637
|
||
III
|
0.0550
±
0.04667
|
0.0560
±
0.04525
|
0.0550
±
0.02970
|
0.1235
±
0.06010
|
0.1155
±
0.05303
|
0.0880
±
0.00141
|
0.1450
±
0.02546
|
||
IV
|
0.1210
±
0.00990
|
0.2360
±
0.14001
|
0.2455
±
0.11809
|
0.2615
±
0.12516
|
0.2235
±
0.04455
|
0.3785
±
0.13789
|
0.5885
±
0.09405
|
||
From
the graph above, the formulation 1 has the highest concentration of
acetylsalicylic acid in the distilled water. Theoretically, low concentration
of acetylsalicylic acid in the distilled water should be shown. That is,
formulation 1 should exhibit slow release properties due to high proportion of
emulsifying wax and low proportion of liquid paraffin. Emulsifying wax
functions to make the acetylsalicylic acid to disperse evenly in the medium
while liquid paraffin helps the acetylsalicylic acid to penetrate the membrane
through diffusion (which in turn illustrates the release profile of the
formulation). Thus, low proportion of liquid paraffin, slow acetylsalicylic
acid release of the formulation should be shown.
The ideal formulation of ointment
has the percentage of emulsifying wax, white soft paraffin and liquid paraffin
at 30%, 50%, 20% respectively. In this combination of ingredients, the
acetylsalicylic acid can diffuse through the membrane better which means that
isotonicity can be achieved between ointment and the surrounding distilled
water in a faster way.
The
graph shown indicates that formulation 2 has higher concentration of
acetylsalicylic acid in distilled water than formulation 3. In formulation 2,
the percentage of emulsifying wax, white soft paraffin and liquid paraffin
should be 34%, 50%, 16% respectively. Meanwhile, in formulation 3, the
percentage of emulsifying wax, white soft paraffin and liquid paraffin should
be 26%, 50%, 24% respectively. Both formulations shows only 4% difference with
the ideal formulation. Thus, these formulations encourage the diffusion of
drugs into the distilled water through the membrane.
Formulation 4 has the lowest concentration
of acetylsalicylic acid in distilled water. Although there is a high amount of
liquid paraffin to assist in the diffusion of acetylsalicylic acid, but
insufficient emulsifying wax causes acetylsalicylic acid unable to disperse
properly in ointment. Therefore, acetylsalicylic acid has low concentration in
distilled water.
As the time goes on, the concentration of
acetylsalicylic acid in distilled water gradually increases for every
formulation.
4. What is the function of emulsifying wax, white
soft paraffin, liquid paraffin, distilled water and acetylsalicylic acid.
Acetylsalicylic acid is the active ingredient of the
ointment and emulsifying wax, white soft paraffin and liquid paraffin serve as
the base. Emulsifying wax is water miscible bases, which composes of
cetostearyl alcohol and sodium laureth sulphate which is surfactant. On the
other hand, white soft paraffin and liquid paraffin are hydrocarbon bases which
have least water holding capacity but most occlusive, they can form an oily
layer on skin, preventing water escape and serves as a protective layer. On the
other hand, emulsifying wax has good water holding capacity because alcohol and
surfactant can form hydrogen bonding with water. Therefore, mixing of bases
enhances water absorption capacity and gets desired physical properties of
ointment.
In this ointment, liquid paraffin serves as oil
phase and emulsifying wax serves as water phase. The phase ratio has to be in
50:50 ratio to ensure stability. If oil phase has more than 70%, it will cause
phase inversion to occur. If oil phase is less than 25%, creaming and cracking
might occur. Therefore, percentage of liquid paraffin and emulsifying wax is
important to ensure stability of the ointment.
Besides that, acetylsalicylic acid is a polar
compound. It will tend to form bonds with alcohol compound of emulsifying wax.
Therefore, amount of emulsifying wax has to be adequate to ensure drug can
dissolve in the base and able to release on skin. Here, the base must has good
drug release profile and non-irritable.
In
conclusion, amount of oil, water and gum has to be followed 4:2:1 and method of
production depends on dry gum method or wet gum method. This is to make sure
the ointment is stable and able to release drug on the skin.
CONCLUSION:
Different
compositions of ointment formulation will affect the rate of release of the
active ingredient. High Emulsifying Wax proportion in an emulsifying ointment
will release drug faster, but will produce a hard ointment. On the other
hand, high liquid paraffin proportion
will increase the spreadability of the ointment which make the ointment easy to be applied on skin
but the ointment will become more greasy and have slower drug release. Thus, we
need to balance between the amount of emulsifying wax and liquid paraffin in
an ointment formulation to achieve an
ideal ointment without affecting the rate of drug release.
REFERENCES:
Paul Beringer, Remington:
The Science And Practice Of Pharmacy, 21th Edition, 2005, Lippincott Williams
& Wilkins.
Aulton, M.E. 2002.
Pharmaceutics: The science of dosage form design. Edinburgh: Churchill
Livingstone.
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