Effects of different ingredients on characteristics of
an ointment formulation
Objectives: To
study the effect of different ointment composition on the physical
characteristics of ointment that is formed and the rate of release of drug from
ointment.
Introduction:
Ointment formulation is a semi-solid preparation that is
applied topically, with protective, therapeutic or prophylactic purposes. In
medical terms, an ointment is defines as a homogeneous, viscous, semi-solid
preparation with a high viscosity, that is used for external application. Ointment is composed mostly of fluid hydrocarbons
meshed in a matrix of higher melting solid hydrocarbons. Generally, an ointment
formulation does not include water and preservatives. The formulation contains
one or more active ingredient(s) dissolved or dispersed homogenously in the
oily phase. A good ointment formulation needs to have to be applied easily to
skin and high rate of release of its active ingredient. Most
ointments are intended to be thick when standing to prevent them from flowing
away from the intended area of use.
Normally, ointment is composed of an active ingredient
(powder or liquid) which is incorporated into an oily semisolid carrier. The
vehicle or base of an ointment is of prime importance for the expected
function of ointment formed. Ointment bases recognized for the use of vehicles
fall into four general classes: hydrocarbon bases, absorption bases,
water-removable bases, and the water-soluble bases. A desired base should not
interfere with the normal functioning of the skin by preventing radiation of
heat from the skin or preventing the excretion of various secretions. It must
not inactivate or interfere with any incorporated medicament. The pharmacologic
effect of a particular drug will be affected greatly by different composition
of base. This includes stability, penetrability, solvent property,
approximately neutral with regard to pH, and ease of application and removal.
Therefore, we need to choose type of bases used carefully to obtain optimum
drug distribution.
This experiment is to find out the effect of different
formulation of ointment on the physical characteristics and the drug release
rate.
Apparatus:
Electronic balance, Weighing boat, 100
ml beaker, Heater, Slap and spatula, Mortar and pestle, 10 cm long Dialysis
bag, Two pieces of threads, Glass rod, Water bath, Pipette and pipette bulb,
Spectrophotometer UV/Vis.
Materials:
Emulsifying Wax, White soft paraffin,
Liquid paraffin, Acetylsalicylic acid, Distilled water.
Procedure
1. 50g
Emulsifying Ointment was prepared using this formula:
|
Emulsifying ointment
|
Group
|
Ingredient (g)
|
Total amount (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
ointment prepared was taken and put into weighing boat and labeled. The
texture, clarity, and color of ointment was described and compared with other
group.
3. 1.5g
of Acetylsalicylic acid was cooperated into 30g ointment using levigation
technique. Before that Acetylsalicylic acid was turn into fine powder using
mortar and pestle.
4. Acetylsalicylic
acid Ointment was filled into dialysis bag and the end of the bag was tied
neatly.
5. Then,
the bag was put into 100ml beaker that contained 50 ml distilled water at 37°C.
6. At
5 minute interval, 3ml solution in the beaker was taken using pipette and the
release of Acetylsalicylic acid from ointment was determined using UV
spectrometer. Before take the sample, the distilled water was stirred first.
|
Time (min)
|
UV absorption
|
||||||||||||
|
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
|
|
UV absorption at 310nm
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Results
And Calculations:
|
Emulsifying Ointment
|
Texture
|
Clarity
|
Color
|
||
|
Spreadibility
|
Hardness
|
Greasiness
|
|||
|
I
|
Very low
|
Very hard
|
Less
greasy
|
Not clear
|
White
|
|
II
|
Low
|
Slightly
hard
|
Slightly
less greasy
|
Not clear
|
White
|
|
III
|
Moderately
spread
|
Soft
|
Greasy
|
Not clear
|
White
|
|
IV
|
Easy to
spread
|
Very soft
|
Very
greasy
|
Not clear
|
White
|
|
Time (min)
|
UV absorption
|
|||||||
|
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
|
|
UV absorption at 310 nm
|
|
0.0682
|
0.0629
|
0.0638
|
0.0748
|
0.1099
|
0.1396
|
0.1669
|
Question and discussion
1.
Compare
the physical shape of the ointment formed and gives your comment.
From the table, all ointments
prepared are not clear in clarity and white in color due to the present of
emulsifying wax and liquid paraffin. This is because emulsifying wax is white
solid which affect both; clarity and color while liquid paraffin is an oily
colorless liquid which affect the clarity only.
Besides that, present of emulsifying wax also
affect the texture of the ointment in term of its spreadibility and hardness.
Reducing amount of emulsifying wax used in ointment cause the ointment becomes
easier to spread and softer. Based on the table, the
hardness of the ointment decreases from ointment I to ointment IV because the
content of emulsifying wax is decreases from ointment I to IV. 9g of
emulsifying wax in ointment IV is not enough to produce “interlocking wax”
structure, thus ointment IV is very soft while ointment I with 21g of
emulsifying wax is very hard. Emulsifying wax prevents the coalescence of
globules of the dispersed phase and increases the viscosity of the ointments.
Thus, high proportion of emulsifying wax in the ointment will decrease the
spread ability of the ointment causes it difficult to be applied onto the skin.
Other
than that, manipulation amount of liquid paraffin in the formulation also
affect the hardness of the ointment. Increasing amount of liquid paraffin
produces softer texture of ointment. In addition, liquid paraffin also plays a
role in greasiness of the ointment. Increasing the proportion of liquid
paraffin in the ointments will increase the greasiness of the ointments due to
its inability to dissolve in water and low water absorbing characteristic. That
is why ointment IV is very greasy as it contains the highest amount of liquid
paraffin and this will aid in the ointment penetration through the skin.
However, increasing greasiness will make it difficult to be removed from the
skin.
2.
Plot graph of UV absorption against time
and give your comment.
From this
experiment, distilled water in the beaker represents the blood circulation in
the body. Since distilled water is hypotonic so acetylsalicylic acid inside the
dialysis bag can diffuse out from the dialysis bag. Acetylsalicylic acid will
diffuse out to the hypotonic solution according to concentration gradient. As a result, the content of acetylsalicylic
acid in the distilled water increases. Dialysis bag acted as phospholipid
bilayer and this experiment is conducted in 37ºC because the temperature mimics
human body temperature. The UV absorption value obtained from the
spectrophotometer represents the amount of acetylsalicylic acid released from
the ointment into the distilled water through the dialysis beg.
Based on the
graph above, it shows that the UV absorption value increases with time. This
means that amount of acetylsalicylic acid in the distilled water increases with
time. The gradient of the graph represents the rate of drug (acetylsalicylic
acid) release to the blood circulation (distilled water). The gradient or rate
of acetylsalicylic acid release is not consistent, some is steeper but some is
less steep. When the gradient is low or at the less steep part, the distilled
water that pipetted out for the test in spectrophotometer is saturated. This is
because it is not stir evenly before taking out the sample. When the UV
absorption value increases, the acetylsalicylic acid release from the dialysis
bag into the surrounding solution also increases. If the saturation occurred,
the graph become constant and the rate of release becomes nearly zero because
the concentration of acetylsalicylic acid in the distilled water is isotonic to
the concentration of ointment.
There might
be some errors that happened and caused the inaccuracy of the results. 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. When we were holding the cuvette, it was not advisable to hold the
smooth surface (where there is a triangle symbol on it).
4.
What is the function of each materials
used in preparation of the ointment? How can different the composition of
Emulsifying wax and Liquid Paraffin can influence the physical properties of
the ointment and the rate of diffusion of the drug from the ointment?
Emulsifying wax is
a type of cosmetic emulsifying ingredient used primarily in the
manufacturing of creams, lotions, and other beauty products. The emulsification
occurs when two substances oil and water — are successfully bound together,
creating a sort of glue that combines the ingredients of a product.
The wax is sometimes labelled as emulsifying wax NF, which
means it meets the standards of a National Formulary, which is a medical manual
containing approved medicines in a particular country — the US, Britain and
Australia are a few countries that have national formularies. When included in a
recipe, emulsifying wax thickens the liquid and marries the oil-
and water-based elements of the creation. The wax itself is made of
either petroleum or vegetable wax that has been enhanced with a
chemical detergent. It is white in color, solid, and possesses a light alcohol
scent. The commonly prescribed amount of emulsifying wax NF is
three to six percent of the total weight of the recipe.
However, liquid paraffin is a type of
hydrocarbon base and is used to reduce the viscosity of ointment or soften the
ointment while white soft paraffin is used as an emollient base in the ointment
formulation.
In this practical,
different amount of emulsifying wax and liquid paraffin is used to prepare 50g
of ointment. Since the emulsifying wax is used to combine the water, oil and
other ingredients together in the ointment, the higher the concentration of the
emulsifying wax, the harder of the ointment produced. For liquid paraffin, its
function is to reduce the viscosity of ointment, thus the higher the
concentration of the liquid paraffin, the lower the viscosity of the ointment
which meant that the ointment is greasier. Hence, the ointment that increased
in the concentration of emulsifying wax and reduced in the amount of liquid
paraffin will be harder and less greasy compare to the ointment that prepared
with the formulation that decreased in the concentration of emulsifying wax and
increased in the amount of liquid paraffin.
When the concentration
of emulsifying wax is increased, the diffusion of the drug will decrease because
emulsifying wax will retard the drug release from the ointment and hence the
diffusion of acetylsalicylic acid from ointment cannot occur perfectly.
However, an optimum concentration of liquid paraffin in ointment will increase
the diffusion rate of acetylsalicylic acid from the dialysis tube because
acetylsalicylic acid which is hydrophilic tends to diffuse into the surrounding
distilled water. The diffusion rate of acetylsalicylic acid will decrease when
the concentration of liquid paraffin is beyond the optimum value. Thus, an
optimum ratio of the phases is needed to produce an ointment with good physical
property and also the drug releasing rate.
Conclusion:
Different ointment
composition have different rate of release of active ingredient from the drug.
Presence of emulsifying wax affects clarity, color and also texture of
ointment. The more emulsifying added in the ointment, the harder the ointment
is. Thus, the spread ability of ointment is decreased. Besides, more liquid
paraffin used causing softer texture and greater greasiness of ointment, hence
it is more difficult to be removed from skin. 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.
Appendix
Emulsifying ointment is prepared by
using emulsifying wax, white soft paraffin and liquid paraffin.
Emulsifying ointment is formed and
cooled at room temperature.
The texture, clarity, colour of
ointment, spreadibility, greasiness, and hardness of the ointment is recorded.
1.5g Acetylsalicylic acid powder is
incorporated into the 15g ointment prepared by using levigation technique.
After finished inserting all the
ointment into the dialysis bag, the dialysis bag was tied at both ends to
prevent leaking of the content.
The bag consisting acetylsalicylic acid
ointment is put into 250ml beaker containing 100ml distilled water that has
been heated to 37ºC.
At time interval of 5 minutes, 3-4ml
aliquot sample is pipette and the release of acetylsalicylic acid from the
ointment base is determined by using UV spectrophotometer
References:
1.
Paul Beringer,
Remington: The Science And Practice Of Pharmacy, 21th Edition, 2005, Lippincott
Williams & Wilkins.
2.
Pharmaceutics: the
science of dosage form design, Aulton, M.E.2002
3.
Jelvehgari, Mitra,
Montazam, Hassan. 2011. Evaluation of mechanical and rheological properties of
metronidazole gel as local delivery system. Archives of Pharmacal Research.
0253-6269
4.
H. C. Ansel, N. G.
Popovich and L. V. Allen, Jr. 2005. Pharmaceutical Dosage Forms and Drug
Delivery Systems, 8th ed., Williams and Wilkins, Baltimore
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