INTRODUCTION:

Effervescent granules are one of the most popular delivery systems for many pharmaceutical products such as antacids, analgesics, and cough/cold formulations. They are unique dosage forms having a drug and effervescent base, composed of sodium hydrogen carbonate, citric acid, and tartaric acid. When added to water, they react to liberate carbon dioxide, resulting in effervescence. The granules are quickly dispersed by the internal liberation of carbon dioxide in water due to interaction between acid and alkali metal carbonated or bicarbonate in the presence of water¹. The liberation of carbon dioxide not only enhances the dissolution of the API in water but also enhances the taste masking effect.

They are already in solution form at the time they are consumed; thus, the drug absorption is faster and more complete. So, they are helpful in treating acute symptoms such as infections and pain^2,3. Some antibiotics and amino acids are sensitive to change in gastric pH and low gastric pH which can lead to their destruction, resulting in their reduced activity. Effervescent granules can increase gastric pH and avoid or minimize the destruction of materials, prone to gastric pH². Metronidazole side effects are notorious for causing heartburn, constipation, and diarrhea. Formulating metronidazole effervescent granules helps us subside the GI upset side effects as they have fewer irritant effects on the gastric mucosa in comparison to conventional tablets and capsules. Many patients find it difficult to swallow tablets and capsules and thus do not comply with prescriptions, which results in a high incidence of non-compliance and ineffective therapy¹. Formulation of metronidazole in the form of effervescent granules not only masks the bitter taste of the drug but also increases its bioavailability by increasing the gastric absorption of the drug⁴.

MATERIALS AND METHODOLOGY:

Materials:

Metronidazole was gifted by Lomus Pharmaceuticals Pvt. Ltd. and other excipients like Citric Acid, Tartaric acid, Sodium bicarbonate, Sodium carbonate, Cetyl alcohol, Sodium starch glycolate and Sodium Saccharine were obtained from Laboratory of CiST College.

Design of Metronidazole Effervescent Granules:

Central Composite Design (CCD) was used to design the formulation which can fit a full quadratic model. A rotatable experimental plan was carried out by a central composite design (CCD) with α=1.414 consisting of 13 experiments. Minitab 17 software was used to design this experment. For two variables (n = 2) and three levels (low (-1), mid (0) and high (+1)), the total number of experiments were 13, determined by 4 cube points, 4 axial points and 5 Centre points.

The variables were selected based on Handbook of Pharmaceutical excipients and various literature review:

For Cetyl alcohol: Low: 2% High: 10%

For sodium starch glycolate: Low: 2%, High: 8%

Table 1: Formulation design of Metronidazole effervescent granules

Cetyl alcohol (%)	Sodium Starch Glycolate (%)
2	2
10	8
6	9.24
2	8
6	5
6	5
6	5
6	0.75
6	5
6	5
11.65	5
10	2
0.34	5

Formulation of Metronidazole Effervescent Granules: The data generated from the design of metronidazole effervescent granules were used to formulate the drug. The concentration of the dependent variables i.e., Cetyl alcohol and sodium starch glycolate for 13 formulations were generated using Minitab statistical software. The fill weight of the formulation was 3000 mg. The concentration in percentage was converted in mg according to the fill weight and the composition for the formulation of metronidazole effervescent granules was obtained. The table below shows the composition of the formulation of effervescent granules for 1 sachet. (Table-2).

Formulation Procedure:

Metronidazole effervescent granules were prepared by melt granulation technique, also known as thermoplastic granulation. The granulation was achieved by the addition of a meltable binders which is in a solid state at room temperature but preferably melts in the temperature range of 50°C-80°C. Further no addition of liquid binder or water was required as the binder in the molten state itself act as a granulating liquid and dried granules can be obtained easily by cooling at room temperature. Meltable binder such as Cetyl alcohol of concentrations 5%, 7.5% and 10% was used in formulation.

Active pharmaceutical ingredient i.e., Metronidazole and all other excipients were weighed and geometrical mixing was done. All the above ingredients were heated at temperature about 50-80°C in a heating mantle until molten state was formed. Then it was cooled down at room temperature and passed through sieve number 20 to obtain granules and finally the granules were dried at temperature not more than 60°C in a hot air oven.

Evaluation of Metronidazole Effervescent Granules:

Standard Calibration Curve:⁵

The linearity of an analytical procedure is its ability to obtain results which are directly proportional to the concentration of analyte in the sample. In order to demonstrate linearity, various concentrations of metronidazole were prepared in 0.1M HCl, i.e. 3ppm, 4ppm, 5ppm, 6ppm, 7ppm and 8ppm. All the concentrations were first scanned in UV range (200-400 nm) for determination of maximum wavelength (λ_max) which was found to be 276 nm. Then corresponding absorbance values were scanned for all the concentrations in λ_max (276 nm)^6,7.

Table 2: Formulation chart of Metronidazole Effervescent Granules

FN	Metronidazole (mg)	Cetyl Alcohol (mg)	SSG (mg)	Citric Acid (mg)	Tartaric acid (mg)	NaHCO₃ (mg)	Saccharin (mg)	Sodium Carbonate (mg)
F1	400	60.00	60.00	1050	9	960	6	455.00
F2	400	300.00	240.00	1050	9	960	6	35.00
F3	400	180.00	277.28	1050	9	960	6	117.72
F4	400	60.00	240.00	1050	9	960	6	275.00
F5	400	180.00	150.00	1050	9	960	6	245.00
F6	400	180.00	150.00	1050	9	960	6	245.00
F7	400	180.00	150.00	1050	9	960	6	245.00
F8	400	180.00	22.72	1050	9	960	6	372.28
F9	400	180.00	150.00	1050	9	960	6	245.00
F10	400	180.00	150.00	1050	9	960	6	245.00
F11	400	349.71	150.00	1050	9	960	6	75.29
F12	400	300.00	60.00	1050	9	960	6	215.00
F13	400	10.29	150.00	1050	9	960	6	414.71

Figure 1: Calibration curve for analysis of Metronidazole

Angle of repose:⁸

Angle of repose is the maximum angle possible between the surface of the pile of powder and the horizontal plane. The lower the angle of repose, better the flow properties⁹. The angle of response is designated by ‘θ’ and given by the following equation.

Tan θ = h/r

Where h = height of the pile

r = radius of the base of the pile

Bulk Density, Tapped density, Compressibility index (Carr’s index) and Hausner’s ratio:¹⁰

10gm of granules was taken in a graduated measuring cylinder and the initial volume was measured⁹. Measuring cylinder containing granules was tapped until no further volume changes occured. Calculation was done using following equations:

Weight of the granules

Bulk density = ---------------------------------------

Apparent volume of the granules

Weight of the granules

Tapped density = ---------------------------------------

Tapped volume of the granules

ρ_t - ρ_b

Compressibility Index (CI) = ------------- x 100

ρ_t

Where, ρ_{t =}Tapped density

ρ_b
=Bulk density

Tapped density (ρ_t)

Hausner’s ratio = ---------------------------------------

Bulk density (ρ_b)

Effervescence Cessation Time:^3,4

Invitro Effervescence cessation time was measured by pouring the one dose of granules in a 250ml beaker containing 100ml of distilled water. Granules from each batch was selected and invitro effervescence time was measured.

In-vitro dissolution Study:¹¹

In-vitro dissolution study was carried using USP TYPE II dissolution apparatus where 900 ml of 0.1N HCl was used as dissolution medium. The temperature of dissolution media was maintained at 37 ± 0.5 °C. The paddle rotation speed was kept at 75 rpm. 5ml of the sample was withdrawn only after 60 min. The samples were analyzed using UV-Vis Spectrophotometer at 276nm.

RESULT AND DISCUSSION:

Physical Evaluation:

The Angle of repose of prepared granules of all formulations were found within the range of 24.645±0.06 to 33.7±0.01. The angle of repose results indicated flow properties ranged from good to excellent. F1, F2, F3, F5, F6, F7 F9 and F10 showed excellent flow properties. F4, F11 and F12 showed good flow properties whereas F8 and F13 showed fair flow properties which might be due to low concentration of Cetyl alcohol and sodium starch glycolate in the formulation. The concentration range of Cetyl alcohol in F13 was 0.34% and the concentration range of Sodium starch glycolate in F8 was 0.75% which was less in comparison with other formulated preparations.

Bulk density was varied from 0.46 ± 0.01 gm/ml to 0.82 ± 0.01gm/ml for 13 batches of formulation. And tapped density varied from 0.50 ± 0.02 gm/ml to 0.86 ± 0.02 gm/ml for 13 batches of formulations. From the tapped density and bulk density, Carr’s compressibility index was calculated.The values of Carr’s index of prepared granules were in the range of 4.61 to 17.39%. The carr’s index results indicated flow properties ranged from fair to excellent. F1, F2, F3, F5, F6, F7, F9 and F10 showed excellent flow properties. F4, F11 and F12 showed good flow properties whereas F8 and F13 showed fair flow properties which might be due to low concentration of sodium starch glycolate and Cetyl alcohol.

The values of Hausner’s ratio of Prepared granules were within the range of 1.04 to1.20. The Hausner’s ratio results indicated flow properties ranged from fair to excellent. F1, F2, F3, F5, F6, F7, F9 and F10 showed excellent flow properties. F4, F11 and F12 showed good flow properties whereas F8 and F13 showed fair flow properties which might be due to low concentration of sodium starch glycolate and Cetyl alcohol.

Table 3: Result of Physical Evaluation of formulated granules

FN	Bulk Density	Tapped Density	Hausner’s Ratio	Carr’s CI	Angle of Repose	Flow Properties
1	0.67±0.01	0.71±0.01	1.05	5.63%	27.63±0.69	Excellent
2	0.82±0.01	0.86±0.02	1.04	4.65%	28.42±0.42	Excellent
3	0.62±0.01	0.65±0.03	1.04	4.61%	24.645±0.06	Excellent
4	0.66±0.02	0.77±0.01	1.16	14.28%	33.335±0.007	Good
5	0.46±0.04	0.5±0.02	1.08	8%	33.7±0.01	Excellent
6	0.46±0.04	0.5±0.02	1.08	8%	33.7±0.01	Excellent
7	0.46±0.04	0.5±0.02	1.08	8%	33.7±0.01	Excellent
8	0.57±0.04	0.68±0.04	1.19	16.17%	27.145±0.007	Fair
9	0.46±0.01	0.5±0.02	1.08	8%	33.7±0.01	Excellent
10	0.46±0.04	0.5±0.02	1.08	8%	33.7±0.01	Excellent
11	0.62±0.02	0.73±0.04	1.17	15.06%	25.765±0.04	Good
12	0.52±0.02	0.6±0.02	1.15	13.34%	26.7±0.59	Good
13	0.57±0.03	0.69±0.04	1.2	17.39%	25.78±0.45	Fair

*Average ± SD, (n=3)

Effervescence Cessation Time:

The values of effervescence cessation time were in the range of 19.5.5±2.12 to 81.5±2.12 seconds. Among all the 13 formulations F5, F6, F7, F9 and F10 showed least effervescent time i.e., 19.5±2.12.

In comparison with other formulations, F2 showed highest effervescent time i.e., 81.5±2.12 which might be due to highest concentration of Cetyl alcohol and sodium starch glycolate than in other formulations. The concertation of Cetyl alcohol and sodium starch glycolate were 10% and 8% respectively and hence the more effervescence time.

Table 4: Effervescence Cessation Time of formulated granules

Formulation Code	Average Effervescec Time
F1	43.5±0.70
F2	81.5±2.12
F3	24.5±0.70
F4	22.5±3.53
F5	19.5±2.12
F6	19.5±2.12
F7	19.5±2.12
F8	29±1.414
F9	19.5±2.12
F10	19.5±2.12
F11	45.5±2.12
F12	60.5±0.70
F13	28±2.82

*Average ± SD, (n=3)

Figure 2: Contour plot of Effervescence time, SSG and Cetyl alcohol

The contour plot generated indicated that the concentration of Cetyl alcohol and sodium starch glycolate possess a significant influence on effervescence cessation time. From the contour plot, it was determined that a less effervescence time (<20%) can be obtained by maintaining Cetyl alcohol concentration range from around 4 to 6% and sodium starch glycolate concentration range from around 4 to 8% respectively.

In vitro Dissolution: According to IP, the limit of % drug release should not be less than 85% of the labelled amount in 60 minutes. The lowest mean % drug release of metronidazole was found to be 87.67% and the highest mean % drug release was found to be 116.34% which is within the IP specifications.

The % amount of drug released after 60 minutes for the 13 formulations of effervescent granules of metronidazole are presented in table. The % drug release of all formulations were found within the range of 87-116% which complies within the IP specifications. F8 showed maximum percentage of drug release i.e. 116.34% which might be due to presence of lower concentration of sodium starch glycolate. This might be the main reason for higher percentage of drug release from formulation F8. The tabulated data showed that the highest percentage release concentration was found to be 116.34 % whereas the lowest percentage release was found to be 87.67%. The dissolution of 6 sachet of effervescent granules varied from 87-90% and 111-116%.

Figure 3: Dissolution study of formulations

Drug Content: According to Pharmacopoeia, the concentration of drug is accepted if it is not less than 90 and not more than 110% of labelled amount. All 13 formulations showed drug content within the range of 90.86 – 100.29 % of labelled amount of drug and complied according to pharmacopoeia.

Figure 4: Drug Content of formulations

Optimization:

Regression Equation for Dissolution:

Dissolution = 124.2 – 2.72 X- 8.41 Y + 0.205 X² + 0.459 Y² + 0.358 XY

Where,

X= Cetyl alcohol

Y= Sodium starch glycolate

Cetyl alcohol has shown retardation of drug release. Sodium starch glycolate has also shown retardation of drug release.

Regression Equation for Effervescence Cessation Time:

Effervescence time: 87.8 -12.42 X – 16.13 Y + 0.906 X² +1.000 Y² + 0.958 XY

Where,

X= Cetyl alcohol

Y= Sodium starch glycolate

Cetyl alcohol has shown the retardation of effervescence time and Sodium starch glycolate has also shown retardation of effervescence time

Overlaid Contour Plot of Effervescence Time and Dissolution:

Figure 5: Overlaid Contour Plot of Effervescence Time and Dissolution.

Effervescence time and Dissolution were taken as optimizing parameters. The optimization was done where; effervescence time and dissolution were taken as a base. The white area in the overlaid contour plot is considered to be the optimized area. Searching around the optimized area showed that, the desired dissolution has to be around 100% and the effervescence time to be around 20 secs. Optimized formulation containing Cetyl alcohol (5.428%) and sodium starch glycolate (3.076%) was found in the white area which estimated the dissolution to be 99.9283% and Effervescent time to be 22.9196 seconds. So the formulation was prepared experimentally using the above mentioned procedure using same ingredients that was used for preparing 13 formulations of metronidazole effervescent granules.

Formulation of Optimized Formulation

S. No.	Ingredients	Amount (mg)
1	Metronidazole	400
2	Cetyl alcohol	162.84 (5.428%)
3	Sodium starch glycolate	92.28 (3.076%)
4	Citric acid monohydrate	1050
5	Tartaric acid	9
6	Sodium Saccharin	6
7	Sodium carbonate	319.88
8	Sodium bicarbonate	960

RESULT OF OPTIMIZED FORMULATION:

Angle of repose, Carr’s Index, Hausner’s ratio were found to be 26.55±0.07, 4.25% and 1.04 respectively which indicated excellent flow properties of the granules.

The concentration of Cetyl alcohol and SSG which were the optimizing parameters, were taken 5.4% and 3.04% respectively. These optimizing parameters resulted in the minimum effervescence time. The effervescence time of the optimized formulation was found to be 19.5±0.70 seconds and the dissolution was found to be 100.1%. The dissolution of Optimized formulation varied from 98.23 to 100.5%. The average assay was 99.32±0.36 which was found within the limit. The concentration of Cetyl alcohol and SSG were 5.428% and 3.076% which was optimum as dissolution nearly equal to that of targeted dissolution (99.92%) was obtained in optimized formulation (i.e. 100.01%)

CONCLUSION:

Higher concentration of Cetyl alcohol resulted in lower effervescence cessation time and higher concentration of SSG and Cetyl alcohol resulted in higher drug release of prepared formulations. Drug content and in vitro drug release of the optimized formulation were 99.32% and 100.01% respectively. So, Metronidazole Effervescent Granules can be an ideal dosage form for geriatric, pediatric patients and dysphagic patients as well. Its advantages including rapid action and increased patient compliance will offer it to be a better alternative to conventional dosage forms.

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Received on 18.08.2023 Revised on 22.04.2024

Accepted on 20.09.2024 Published on 17.12.2024

Available online on December 23, 2024

Asian Journal of Pharmaceutical Research. 2024; 14(4):349-354.

DOI: 10.52711/2231-5691.2024.00055