INTRODUCTION:

Since decades among all the pharmaceutical products available, oral drug delivery had gained a higher scope and popularity and had been widely employed for the systemic delivery of drug. The positive aspect regarding the oral dosage form which created its high level of acceptance was its case of administration, patient compliance and stability in the formulation¹. Reconstitutable oral suspension can be administered immediately. There is an important category of suspension that requires mixing prior to administration. These are dry mixtures that require the addition of water at the time of dispensing. The reconstituted system is the formulation of choice when the drug stability is a major concern.

After reconstitution, these systems have a short but acceptable life if stored at refrigerator temperatures^2,3.The required properties can be maintained before and after reconstitution. Reconstitutable oral systems have adequate drug stability during the shelf life. It also reduces the weight of the final product because the aqueous vehicle is absent and consequently the transportation expenses may be reduced.

Ornidazole, chemically 1-chloro-3-(2-methyl-5-nitro-1H-imidazol-1-yl) propan-2-ol, with molecular formula C₇H₁₀N₃O₃Cl is an antimicrobial agent. Ornidazole is used in the treatment of amoebiasis, giardiasis, trichomoniasis etc. This drug is under the category anthelmentics^4.Ornidazole is a 5-nitroimidazole derivative. It is converted to reduction products that interact with DNA to cause destruction of helical DNA structure and strand leading to a protein synthesis inhibition and cell death in susceptible organisms^5.It is an official drug in Indian pharmacopoeia. Suspensions are uniform dispersion of solid drug particles in a vehicle in which the drug has minimum solubility. It is more favoured than solid because of the flexible dosage administration and easy to swallow⁶.Dry suspension is commercial dry mixtures that require addition of water at the time of dispensing⁷. Reconstitutable oral systems show adequate chemical stability of the drug during shelf life, avoids the physical stability problems related to solubility, pH, and incompatibilities with other ingredients and also reduce the weight of the final product because the aqueous vehicle is absent and consequently the transportation expenses may be reduced^8-11. In the present study, Ornidazole is employed in the powder form for improving its stability and dissolution rate.

MATERIALS AND METHODS:

Materials:

Ornidazole was obtained as a gift sample from M/S Life Line Formulations., Vijayawada. Sodium carboxy methylcellulose and Xanthan gum were procured from yarrow Chem Pharma Limited, Mumbai. Sodium alginate was procured from Loba Chemie Pvt Ltd., Mumbai. Sodium benzoate was procured from S.D Fine Chem. Ltd., Mumbai.

Preparation of ornidazole reconstitutable suspensions:

Dry suspensions of Ornidazole (500mg/5ml) was prepared using suspending agents, sweetener, preservative, buffer, flavoring and anticacking agent by employing different techniques like physical mixing, co grinding and solvent evaporation method. Trial and error method was followed to reach the optimum formulation using different quantities of excipients. All ingredients were passed through 120# and then mixed by geometric dilution. Dose of powder mixture i.e., 1 part is equivalent to 500mg of ornidazole. Preparations then transferred to homogenizer and homogenized for 15 minutes. Finally volume and pH were adjusted wherever

required. The various formulations prepared are listed in Table1.

Evaluation of Flow Properties of Oral Reconstitutable Systems:

Angle of Repose:

The powder flow properties were determined by two open side method. In this process powder is taken into a funnel through which the powder to be calculated to its angle of repose is poured through funnel below this graph sheet is placed and allowed it to flow during this process material will form a heap like structure for which we can measure its radius and its height of the heap by using the formula;

q =tan^-1(h/r)

Carr’s Index:

A simple test was used to evaluate the flowability of a powder by comparing the poured density and the tapped density of a powder and the rate at which it is packed down. A useful empirical guide is given as carr’s compressibility index¹². Carr’s index = Tapped density – Poured density X 100/Tapped density

Stability Evaluation of Oral Reconstitutable Suspensions:

Oral Reconstitutable System of Ornidazole was evaluated for organoleptic properties, microscopy, flow properties, rheological and sedimentation behavior, drug content and in vitro drug release.

Sedimentation Volume:

Sedimentation volume (Vs) is nothing but a ratio of the final volume of sediment (Hu) to the original volume of sediment (Ho) before settling. 20ml of each suspension was transferred to 25ml measuring cylinders and the volume of sediment formed was noted. The sedimentation volume (F) was calculated using the formula.

Vs = Hu /Ho

Where Hu = ultimate height of the sediment; Ho = initial height of the total suspension. The larger this fraction, the better is the suspend ability. The height of the sediment was noted at particular time intervals. The Hu/Ho ratios were obtained and plotted as ordinates with time as the abscissa.

Ease of Re-dispersibility:

Ease of redispersion is a qualitative evaluation. The suspension was allowed to settle in a measuring cylinder. The mouth of the cylinder was closed and was inverted through 180⁰ and the number of inversions necessary to restore a homogenous suspension was determined. If the homogeneity of the suspension was attained in one inversion, then the suspension was considered 100% easily re-dispersible. Every additional inversion decreases the percentage of ease of re-dispersibility by 5%. This process was repeated continuously until the sediment was completely re-dispersed.

Particle Size:

The properties of a liquid oral suspension of active substance are greatly influenced by the particle size of the suspended active substance. It was measured by microscopy.Using optical microscope particle size distribution studies were carried out.

1. Eye piece micrometer was calibrated using stage micrometer.

2. Sample was uniformly suspended in a clean glass slide

3. A slide of the above suspension was prepared, placed under microscope and measured the size of the particles. The size of 100 particles was measured and the average particle size was determined.

Viscosity Measurement:

The rheological profile of each formulation after constitution, in terms of viscosity, was determined by using the Ostwald Viscometer. Rheologic methods can help in determining the settling behavior of the dry suspension. Viscosities were determined in triplicate.

Drug Content Estimation:

One dose of dry suspension (500mg of the formulation in 5ml) is equivalent to 500mg of Ornidazole. 0.25ml of suspension was extracted with 10 ml of methanol and the solution was filtered through Whatman filter paper. 1 ml of the above solution was diluted to10ml with 0.1N HCl. And from this 0.5ml of solution was further diluted to 10ml with 0.1N HCl. The absorbance of the solution was read at λmax 318 nm on ELICO UV-3000+ Double Beam Spectrophotometer.

In- vitro dissolution studies of oral reconstitutable suspension:

Dissolution studies on each formulation were performed in a calibrated 8 station dissolution test apparatus (LABINDIA) equipped with paddles (USP apparatus II method) employing 900ml of 0.1N HCl as a medium. The paddles were operated at 50rpm and temperature was maintained at 37ºC±1º C throughout the experiment. The samples were withdrawn at 90 mins and replaced with equal volume of same dissolution medium to maintain the constant volume throughout the experiment. Samples with drawn at various time intervals were suitably diluted with same dissolution medium and the amount of the drug dissolved was estimated by ELICO double beam U.V spectrophotometer at 318nm. The dissolution studies on each formulation were conducted in triplicate. From the dissolution profiles various parameters like T_50,T₉₀ and DE_30% were calculated. The dissolution profiles for all formulations were shown in figures 1-3.

Pharmacokinetics of The Drug Release:

Pharmacokinetic parameters such as zero order; first order were calculated from the dissolution data obtained for various formulations. The data of various pharmacokinetic parameters were given in table 3.

Zero Order:

A plot of Cumulative % drug released Vs Time (min) was plotted. Zero order release rate constant (K_o) was obtained.

First Order:

A plot of log % drug undissolved Vs time (min) was plotted for all the formulations and the first order release rate constant (K₁) was calculated by multiplying slope with 2.303. The following mathematical expressions were used to calculate various pharmacokinetic parameters from the dissolution data.

Zero Order Equation:

Cumulative % drug released = K_ot --------------------- (1)

Where, K_o–Constant; t - Time

First Order Equation:

log % drug undissolved = K₁t /2.303

ACCELERATED STABILITY STUDIES:

The formulations which showed good invitro performance were subjected to accelerated stability studies. These studies were carried out by investigating the effect of temperature on the physical properties and chemical stability of reconstituted suspension containing drugs. The prepared formulations such as OFS₂& OFC₂ were subjected to accelerated stability studies. The above said formulations were kept in Petri dishes after preparation and stored in thermo stated oven at a temperature and relative humidity of 25±2⁰C, 60±5% RH for 6 months and 40±2⁰C, 75±5% RH for 3 months. Then the samples of each type of formulation wereanalyzed for viscosity, re-dispersibility, sedimentation volume, drug content and in vitro dissolution profile.

DISCUSSION OF RESULTS:

Reconstitutable suspensions are powdered or granular formulations prepared for reconstitution. They are filled up to volume by liquid, normally warm water, just before use. Most of the medicaments formulated for reconstitution belong to the group of antibiotics. A dry suspension offers several advantages such as maintenance of the chemical stability of the active compounds until reconstitutions at the start of treatment. In the present study, Ornidazole is employed in the powder form for improving its stability and dissolution rate.

Ornidazole is an antibiotic used to treat some protozoan infections. It has also been investigated for use in Crohn's disease after bowel resection. It is White or slightly yellowish powder. It is well absorbed by oral route. Its oral bioavailability is 65% ±15 and having 15% plasma proteins binding. It is metabolized via the liver, excreted in the urine and feces. Based on these biopharmaceutical properties Ornidazole is selected as a drug candidate for formulation as reconstituted suspension. Powder blends were prepared by physical mixing, solvent evaporation and co-grinding methods. They were evaluated for flow properties, sedimentation rate, viscosity, particle size and drug release studies. Pre-formulation studies were performed on the Ornidazole and excipients used in the formulations were found to be compatible. No drug and excipients reactions were observed. Saturated solubility studies were conducted for Ornidazole using different dissolution media. Ornidazole showed maximum solubility in 0.1N HCl medium. Dry Suspensions were prepared by physical mixing, solvent evaporation and co-grinding methods using Xanthan Gum, sodium CMC, Guar Gum and Sodium alginate (S.A) suspending agents the formulations were found to be stable and suitable for increasing the dissolution rate of Ornidazole and composition was shown in table 1

Table1: Composition of Ornidazole Dry Suspensions

Ingredients

OFP1

OFP 2

OFP 3

OFP 4

OFS1

OFS 2

OFS 3

OFS 4

OFC1

OFC 2

OFC 3

OFC4

Ornidazole

5.0g

X.G (1%)

50mg

SCMC (1%)

50mg

Guar Gum (1%)

50mg

S.A (1%)

50mg

Sucrose

0.850g

0.850 g

0.850g

Sodium Benzoate

0.1g

Pineapple flavor

q.s

Total Wt.(gms)

Note:1 part is equivalent to 500mg(OFP1, OFP2, OFP3, OFP4, OFS1, OSF2, OSF3, OSF4 OFC1, OFC2, OFC3 & OFC4 codes used for ornidazole reconstituted suspension by using physical mixing, solvent evaporation and cogrinding method)

Table 2: Evaluation data of Ornidazole Oral Reconstitutable Systems

S.No	Formulation	Angle of Repose (º)	Carr’s Index	Sedimentation Volume (Vs)	Viscosity ‘η’ (cps)	Re-dispersibility
	OFP1	25	19	0.98	2.77	Re-dispersible
	OFP2	23	16	0.99	2.00	Re-dispersible
	OFP3	26	14	0.89	5.54	Not Re-dispersible
	OFP4	23	18	0.65	2.31	Re-dispersible
	OFS1	20	16	0.96	4.23	Re-dispersible
	OFS2	21	17	0.98	3.21	Re-dispersible
	OFS3	24	17	0.92	5.64	Not Re-dispersible
	OFS4	25	19	0.35	3.26	Re-dispersible
	OFC1	26	13	0.97	3.41	Re-dispersible
	OFC2	20	12	0.98	2.63	Re-dispersible
	OFC3	23	17	0.99	5.79	Not Re-dispersible
	OFC4	26	17	0.53	3.53	Re-dispersible

The reconstituted suspensions formulation OFP1 which was formulated by using Xanthan Gum (1%) showed an average drug release of 72.64% within 45 min. The reconstituted suspensions formulation OFP2 which was formulated by using Sodium Carboxy Methylcellulose (1%) showed an average drug release of 77.51% within 45 min. The reconstituted suspensions formulation OFP3 which was formulated by using Guar gum (1%) showed an average drug release of 69.54% within 45 min. The reconstituted suspensions formulation OFP4 which was formulated by using Sodium Alginate (1%) showed an average drug release of 64.35% within 45 min.

The reconstituted suspensions formulation OFS1 which was formulated by using Xanthan Gum (1%) showed an average drug release of 75.14% within 45 min. The reconstituted suspensions formulation OFS2which was formulated by using Sodium Carboxy Methylcellulose (1%) showed an average drug release of 80.450% within 45 min. The reconstituted suspensions formulation OFS3 which was formulated by using Guar Gum (1%) showed an average drug release of 80.63% within 45 min. The reconstituted suspensions formulation OFS4 which was formulated by using Sodium Alginate (1%) showed an average drug release of 72.27% within 45 min.

The reconstituted suspensions formulation OFC1 which was formulated by using Xanthan gum (1%) showed an average drug release of 80.69% within 45 min. The reconstituted suspensions formulation OFC2 which was formulated by using Sodium Carboxy Methylcellulose (1%) showed an average drug release of 84.45% within 45 min. The reconstituted suspensions formulation OFC3 which was formulated by using Guar Gum (1%) showed an average drug release of 77.51% within 45 min. The reconstituted suspensions formulation OFC4 which was formulated by using Sodium Alginate (1%) showed an average drug release of 74.22% within 45 min.

All the reconstituted suspensions formulations were found to be linear with first order release rate with R² values in the range of 0.8915 - 0.9958. Thus, the rate of drug release from all the reconstituted suspensions formulations were concentration dependent and was linear with first order release rate constant (K₁).The drug release from the formulations was by diffusion of the drug from the suspending agent, followed by erosion. Drug release profiles and their kinetic data were shown in figure 2 - 3 & table 3.

Figure 1: Dissolution profile curve of Ornidazole Reconstituted Suspension (Physical Mixing& Solvent Evaporation Method)

Figure 2: Dissolution profile curve of Ornidazole Reconstituted Suspension (Co Grinding Method)

Table 3: Dissolution Parameters of Ornidazole Reconstituted Suspension

Formulation	Zero Order K	Zero Order R²	First order K(min^-1)	First order R²	T 50%	T 90%	DE30%
Pure Drug	1.138	0.6041	0.006	0.8915	30	>90	50
OFP1	1.727	0.6516	0.0232	0.9852	7	>90	65.3
OFP2	1.682	0.6789	0.0166	0.9886	5	80	63.3
OFP3	1.556	0.6611	0.0140	0.9832	10	>90	68.2
OFP4	1.456	0.6495	0.0121	0.9857	12	>90	58.3
OFS1	1.707	0.6076	0.0298	0.9306	3.5	82	73.3
OFS2	1.588	0.5919	0.0209	0.9937	3	65	70.0
OFS3	1.613	0.6288	0.0198	0.9642	4	85	78.2
OFS4	1.539	0.6242	0.0164	0.9958	4.5	>90	73.3
OFC1	1.670	0.5796	0.0318	0.9745	3.5	82	65.2
OFC2	1.677	0.6105	0.0253	0.9862	3	65	70.0
OFC3	1.647	0.6276	0.0218	0.984	4	85	66.2
OFC4	1.575	0.6412	0.0184	0.9898	4.5	>90	62.5

The in vitro dissolution studies were performed for various reconstituted suspensions in 1.2 pH acidic medium. It is found that the formulations OFS2 and OFC2 prepared by solvent evaporation and Co-grinding methods released the drug rapidly than the pure drug and other formulations. The drug releases from all the prepared reconstituted suspensions were found to depend on the nature of suspending agent used. The order of release of drug is SCMC>Xanthan Gum > Sodium Alginate > Guar Gum. The drug release from all the reconstituted suspensions were followed first order rate kinetics and R² values of all the formulations were in the range of 0.852 to 0.997.

Accelerated stability studies were carried out for selected formulations. There was no significant change observed in physical parameters such as viscosity, redispersibility, sedimentation volume, drug content and in- vitro dissolution profile. Drug release from the optimized formulations after storage at different conditions remains unaltered and found to be quite stable. The graph was shown in figure3

Figure 3: Dissolution profile curve of optimized Ornidazole Reconstituted Suspension (OFS2)

CONCLUSION:

In the present study, an attempt was made to formulate Ornidazoleby using various techniques with different suspending agents. From the above results and discussions, it was found that the drug was released at a faster rate compared to pure drug. The drug released from the OFS2 was very rapid compared with that of pure drug and other formulations which were due to porous puffy network like formulation of dry suspension prepared by solvent evaporation method. In evaluating period of 7days no significant change was observed in various evaluation parameters. This method is simple and cost effective to prepare that may be acceptable to the industry.

ACKNOWLEDGMENTS:

The authors expressed their gratitude to M/S Life Line Formulations for providing the gift samples. The authors are also thankful to the management of Chebrolu Hanumaiah Institute of Pharmaceutical Sciences, Guntur for providing the necessary facilities to carry out the research work.

ABBREVIATIONS:

Sodium Carboxy methylcellulose (SCMC) and sodium alginate (SA), Hydrochloric acid (HCl), Dissolution Efficiency at 30 min (D.E30%), Centi poise (CPS), Xanthan Gum(X.G), Relative Humidity(RH), Fourier transform infrared spectroscopy (FTIR), differential scanning Colorimetry (DSC), Ultra- Violet(UV).

CONFLICT OF INTEREST:

The authors declare no conflict of interest

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Received on 27.10.2021 Modified on 22.05.2022

Research J. Pharm. and Tech 2023; 16(7):3289-3294.

DOI: 10.52711/0974-360X.2023.00542