Monday, 8 June 2015

Experiment 4: Evaluation of the effect of different formulations on suppository characteristics.

Title:
Evaluation of the effect of different formulations on suppository characteristics.

Objectives:
1.      To study the effect of different composition of bases on the physical characteristics of suppositories.
2.      To determine the effects of different composition of bases on the rate of drug release.

Introduction:

Suppository is a solid formulation of different sizes and shapes suitable for rectal, vaginal or urethral drug administration where it dissolves or melts and is absorbed into the bloodstream. The ideal suppository  is generally conical or bullet-shaped and should have all these properties where it must be able to melt at body temperature, 370C, non irritating, physically and chemically stable, inert, high viscosity when melted. It should be able to release the drug locally or systemically. The advantage of suppository is that it can prevent first pass effect , avoid the digestive enzymes and thus increase bioavailability. But, suppository have some disadvantages. It can cause mucosal irritation, patience compliance problems, erratic and undesired absorption.

The drug needs to be dispersed in suitable suppository bases. Good bases are non-toxic, do not cause irritation, do not interact with other drugs and also easy to be mould into a suppository. Different composition of base will affect the rate and limit of release of the drug from the suppository. If a drug is more soluble in base, this will slow down the release rate of drug from suppository. On the contrary, a drug which is less soluble in base will be more readily released.

In this experiment, the effects of the different base composition to the suppository physical characteristics and also to the drug release characteristics are evaluated. Water-soluble base, polyethylene glycol is used.

Apparatus:
Analytical balance, weighing boats, spatula, 50ml and 100ml beaker, hotplate, 5ml measuring cylinder, suppository mould, water bath 37oC, dialysis bag, glass rod, 5ml pipette,  plastic cuvette, UV spectrophotometer

Materials:
Polyethylene glycol (PEG) 1000, Polyethylene glycol (PEG) 6000, paracetamol, distilled water, 2 strands of thread


Methods:

1.      Paracetamol saturated stock solution is prepared by adding 10g of Paracetamol in 5ml distilled water.

2.      The 10g suppository is prepared using the formulation below:

Suppository
Group
PEG 1000
(g)
PEG 6000
 (g)
Paracetamol stock solution (ml)
Total
(g)
I
1,5
9
0
1
10
II
2,6
6
3
1
10
III
3,7
3
6
1
10
IV
4,8
0
9
1
10
3. Suppositories are shaped by using suppository-mould. The shape, texture, and colour of the suppositories are examined.
4. 1 suppository is placed into the beaker containing 10ml of saline water at 370C and time required to melt the suppository is recorded.
5.1 suppository is filled into dialysis bag. Two terminal end of the bag is assured to be tied up neatly using thread. The dialysis bag is placed into the 100ml beaker which containing 50ml saline water being heated up to 370C.
6. An aliquot sample with 3-4ml is pipette at 5 minutes interval. The rate of release of paracetamol from the suppository is determined using UV-visible spectrometer. Make sure saline water is stirred by glass rod before sample is taken out.



Results:
1. Compare the physical appearance of the suppository formed.
Suppository
Group
Material (g)
Shape
Greasiness
Hardness
Colour
PEG 1000
PEG 6000
I
1,5
9
0
Bullet-shaped
Very greasy
Very soft
White, opaque
II
2,6
6
3
Bullet-shaped
Moderately greasy
Soft
White, opaque
III
3,7
3
6
Bullet-shaped
Greasy
Hard
White, slightly transparent
IV
4,8
0
9
Bullet-shaped
Least greasy
Very hard
White, transparent

Discussion:

The shape of all the suppositories produced by each group are the same which is the bullet-shaped due to the same shape of the moulds used. This particular shape of suppositories eases the administration of suppository into the rectum. The difference in the quantity of PEG 1000 and PEG 6000 used by each group lead to the formation of suppositories with different physical characteristics.
 PEG 1000 is a soft solid whereas PEG 6000 is a hard solid due to the difference in the molecular weight between them. The hardness of the suppositories increases when the amount of PEG 6000 increases. This is because PEG 6000 contains higher content of hydroxyl groups within the structure. More of intra-molecular and inter-molecular hydrogen bonds are formed between PEG molecules, thus rendering the overall structure strength. Therefore, using a higher ratio of PEG 6000 to PEG 1000 will result in a harder suppository. Therefore, the hardness of suppository increases from formulation of suppository I to IV.
 Besides that, suppository I to IV has decreasing greasy properties due to the decreasing of the composition of PEG 1000. PEG 1000 is less hydrophilic and has more lipophilic property. Therefore, suppository with the high content of PEG 1000 will result in the formation of more greasy suppository. For example, the suppository with formulation I is very greasy meanwhile for the suppository with formulation IV is the least greasy and very dry due to the absence of the PEG 1000.
Finally, as for the colour of suppositories, since the active ingredient that we used is paracetamol which is white in colour, the colour of the suppositories produce will take on the same white colour too but differ in the transparency degree. The formulation with the lowest amount of PEG 1000 is more transparent compared to the others.


2. Plot a graph of time needed to melt suppository versus amount of PEG 6000 in the formulation. Compare and discuss the result.
Amount of PEG 6000 (g)
0
3
6
9
Groups
1
5
2
6
3
7
4
8
Time (min)
56.0
61.0
58.75
52.0
27.45
31.06
48.63
56.0



Amount of PEG 6000 (g)
0
3
6
9
Average of time (min) (¯x ± SD)
58.5 ± 2.5
55.38 ± 3.38
29.53 ± 1.81
52.32 ± 3.69




Discussion:
In this experiment, PEG is used as the suppository base. Two types of PEG which are PEG 1000 and PEG 6000 are being used in this experiment. A graph of mean time versus amount of PEG 6000 has been plotted. The suppository is placed in a beaker containing 10mL distilled water with temperature of 370C and the time needed to melt the whole suppository is recorded.
PEG 6000 is a suppository base and theoretically, increasing the mass of the PEG 6000 will make the suppository more solid because the molecular weight is increased. The presence of hydroxyl (OH) group in the suppository cause increase in time for the suppository to melt. The higher the amount of PEG 6000 used, the more the OH group that will be present in the suppository. Therefore, there will be more hydroxyl group forming hydrogen bond with paracetamol. With the increase in the formation of hydrogen bond, the suppository formed will be harder and time needed to completely melt the suppository will increase in water. This is because time needed for the dissociation of the hydrogen bond is more difficult with the increase in the formation of the hydrogen bond. Thus, the time taken for the suppository to melt should actually increases with the increasing amount of PEG 6000 in the suppository.
  Based on the graph above, the time needed for the suppository with 0g of PEG 6000 to melt is supposed to be the shortest. However, the results deviate for the suppositories that contain 0, 3, 6 g of PEG 6000 g. For this 3 suppositories, the average time needed decreases with the increasing amount of PEG 6000, with suppository 0g requiring the longest time to melt. This shows that the results we obtained is inappropriate and does not comply to the theory. Errors may have occurred in the procedure of this experiment. Besides that, from the graph, it can be seen that the average time needed for the suppository with 9g PEG 6000 increases abruptly after the lowest duration of time recorded which was for suppository with 6g PEG 6000 to melt. The time taken for suppository containing 9g PEG 6000 to melt measured by both Group 4 and Group 8 has a large difference. The time taken for suppository to melt measured by Group 4 is shorter while Group 8 is much longer. They are not around the same range.
The deviation and inaccuracy of the result is majorly affected by the errors occured while conducting the experiment. Error made during measuring and transferring the ingredient while making suppository may alter the results. Moreover, deviation of the temperature of the water bath by different groups where higher temperature will increase the melting of the suppository, producing the shorter time needed cause inaccuracy in the results. Another cause may due to some of the group might stir the beaker containing suppository which make it faster to dissolve.    Hence, these errors have to be avoided in order to improve the accuracy of the experimental result.



1.       For each 5 minutes, an aliquot sample (3-4mL) is pipette and determines the release of Paracetamol from the suppository by the spectrometer UV-visible. Make sure the distilled water is stir with the glass rod before the sample is taken.

Time (min)
UV-visible Absorption
0
5
10
15
20
25
30
UV absorption at 520nm
0.033
0.038
0.043
0.048
0.097
0.260
0.314



Discussion:

Based on the graph, the rate of release of Paracetamol was slow initially but increased gradually over time. The reading of UV absorption remain constant between the 10th to 15th minute. This is due to the wax that coat the active ingredients was not fully dissolved yet. After the 15th minute, the reading of UV absorption increased tremendously because the wax coating has dissolved completely and released higher amounts of active ingredient.

  
1.       Plot graph of UV absorption against time for the suppository formulation with different compositions. Discuss and compare the results. 






Discussion:

From the graph above, the results obtained from the experiment are inaccurate. The readings for the suppository I,II,III and IV is not increasing gradually which maybe due to experimental errors described below. Theoretically, all the graphs should be in sigmoid shape. Suppository may initially dissolve slowly and paracetamol diffuse from the dialysis bag into water in beaker. Thus, the paracetamol concentration in water will be increased by time until all paracetamol are released and become saturated in water, then the paracetamol concentration will be constant.
From this graph, it shows that different formulation of suppository give rise to different rate of drug release profile. The releasing rate of paracetomol is measured by spectrometry. According to theory, suppository IV which contains the greatest amount of PEG 6000 will give the lowest rate of drug releasing. This is because the higher amount of hydrogen bonds formed between the base molecules and the paracetamol molecules. This causes the drug molecules (paracetamol), to be held stronger in the formulation and thus exert a lower releasing rate. The reading from the spectrometry should show an increasing trend but a slowest rate. The drug releasing rate from the suppository I should be the highest theoretically because it does not consist of PEG 6000. The graph obtained should be increasing initially and then become constant gradually as all the drug is released into the water.
However,in the experiment, suppository I which does not contain PEG 6000 gives a lower paracetamol release rate compared to other suppositories because presence of PEG 1000 also allow paracetamol delivery of the suppository into the rectum. Suppository II contains PEG-6000 that can be used as a drug delivery agent to increase drug release so it has higher paracetamol release rate compared to suppository I. The appropriate percentage for PEG suppository is 40% PEG 1000 and 60% PEG 6000. Suppository III shows the most ideal combination whereby percentage of PEG 1000 is 33.3% and that of PEG 6000 is 66.7%. So, suppository III should have the highest paracetamol release rate. However, according to the graph from the experiment, suppository III graph is not the highest according to the theory. This may due to the technique and experimental error during experiment as the suppository II graph is not a sigmoid shape. Suppository IV which contains the highest amount of PEG 6000 will give the lowest paracetamol release rate. This is due to the higher amount of hydrogen bonds formed between the PEG base molecules and the paracetamol molecules. This causes the paracetamol to be held stronger in the suppository formulation, resulting in a lower releasing rate. The reading for supository IV is ideal since the reading was slowly increase and highest at 30 minutes of the experiment showing that it have slower release rate.
The inaccurate results obtained maybe due to several errors, such as the errors in the preparation of the suppositories or there is presence of impurities in the formed suppositories. Besides, the uneven stirring process before the content of the mixture is pipetted also can contribute to the inaccuracy of the results which form a few small fluctuations in the line graph. Some precaution steps should be carried out to obtain an accurate result. The surface of dialysis bag should be cleaned before immersing it into the distilled water and suppository should be filled into the bag carefully to prevent breakage of the bag. Mould of suppository must wait until it become solid and make sure the paracetamol disperse well in the suppository. Thus, errors must be avoided and special precautions must be taken to achieve a successful experiment.



5. What is the function of each ingredient that is used in the preparation of these suppositories? How does the usage of different content of PEG 1000 and PEG 6000 affect the physical properties of suppository formulation and rate of releasing of drug from it?

There are three ingredients used in the experiment which are paracetamol, polyethylene glycol ( PEG) 1000 and polyethylene glycol ( PEG) 6000. Paracetamol is a drug that is used as the active ingredient for this suppository. It is an antipyretic and analgesic agent. It is commonly used to treat fever. PEG 1000 and PEG 6000 are used as base in this suppository and is medicinally used as laxative for short term relief of constipation. PEG assists in extended release of drug from the dosage form. PEG is water-soluble polymer, it can be used to create very high osmotic pressures.
A suitable combination of PEG allows an optimum drug release, in which the drug will not be held strongly in the base and can be easily released. This is important to allow an optimum drug bioavailability to take place as the drug can be absorbed by mucosa membrane of the rectal. The PEG shows high stability and the desired solidity can be adjusted by choosing desired combinations of PEG. The PEG 1000 and PEG 6000 represent PEG with different molecular weight. PEG 1000 has smaller molecular weight compared to  PEG 6000.
PEG 6000 has decreased solubility in water and solvent, and has higher melting point compared to PEG 1000. So, the suppository with high proportion of PEG 6000 will dissolve slowly in water. Suppository with high amount of PEG 1000 will dissolve faster in water. The suppository produced from PEG 1000 will tend to be softer and suppository made from PEG 6000 will be harder. The rate of drug release from the dialysis bag will be faster when PEG 1000 is used as base compared to PEG 6000. This is due to less solubility of high molecular weight of PEG in water. So, the suppository with PEG 6000 that is less soluble will release the drug content in the suppository slowly in water.


Conclusion
The suppository composition will affect the physical property and the drug release rate from the suppository. Different percentage combination of PEG 6000 and PEG 1000 determines the properties of a suppository. The higher the amount of PEG 6000, the harder the suppository and less soluble in water. 


References: