International Journal of Nutrition, Pharmacology, Neurological Diseases

ORIGINAL ARTICLE
Year
: 2021  |  Volume : 11  |  Issue : 4  |  Page : 279--286

Preparation and evaluation of sustained release dosage forms for posttransplant care


Mullaicharam Bhupathyraaj1, Alka Ahuja1, Nirmala Halligudi1, Sushma Pole1, Hiba Salim Al Balushi1, Halima Ahmed Al Kaabi1, Saleem M Desai2,  
1 College of Pharmacy, National University of science and Technology, Muscat, Sultanate of Oman
2 Rani Channamma University, Balagavi, Karnataka, India

Correspondence Address:
Mullaicharam Bhupathyraaj
National University of science and Technology, Muscat
Sultanate of Oman

Abstract

Aim: The purpose of the study was to prepare and characterize microbeads for oral sustained release of tacrolimus. Design, methodology, and approach: Tacrolimus-based microbeads were developed by ionic gelation method. Xanthan gum, chitosan, and sodium alginate were used as polymers for aqueous internal phase using calcium chloride as a cross-linking agent. The microbeads were evaluated for morphologic features by scanning electron microscopy, percentage yield, drug entrapment, and in vitro drug release. Findings and implications: Microbeads were examined for the effects of various variables in formulation process. The cross-linking reaction between sodium alginate and calcium chloride for being converted into calcium alginate in the formulation process was used in the microencapsulation of tacrolimus core material. The results showed the compatibility of the drug with the polymers in the formulation as observed in Fourier-transform infrared spectroscopy studies. The formulated microbeads showed high percentage yield and drug entrapment efficacy and the optimized formulation showed a delayed release effect following zero-order mechanism of release. Conclusion: Ionotropic gelation method was found to be a suitable method for preparing tacrolimus microbead-sustained-release drug delivery system. Chitosan and xanthan gum polymers showed potential in aiding the formulation of sustained release tacrolimus microbeads. Xanthan gum is soluble in water and confers high viscosity at low concentrations. The molecular weight of xanthan gum is more than the chitosan polymer which leads to better sustained release of microbeads prepared with xanthan gum compared to chitosan microbeads. Both chitosan and xanthan gum microbeads followed zero-order-release kinetic models.



How to cite this article:
Bhupathyraaj M, Ahuja A, Halligudi N, Pole S, Al Balushi HS, Al Kaabi HA, Desai SM. Preparation and evaluation of sustained release dosage forms for posttransplant care.Int J Nutr Pharmacol Neurol Dis 2021;11:279-286


How to cite this URL:
Bhupathyraaj M, Ahuja A, Halligudi N, Pole S, Al Balushi HS, Al Kaabi HA, Desai SM. Preparation and evaluation of sustained release dosage forms for posttransplant care. Int J Nutr Pharmacol Neurol Dis [serial online] 2021 [cited 2021 Dec 3 ];11:279-286
Available from: https://www.ijnpnd.com/text.asp?2021/11/4/279/329202


Full Text



 Introduction



Multiparticulate beads have been prepared via ionotropic gelation technique using polymers such as chitosan, xanthan gum, and sodium alginate to counter ions such as calcium chloride to produce insoluble meshwork in the form of beads that would provide the sustained drug release.[1],[2],[3],[4]

Tacrolimus (FK506), a typical immune depressant, was isolated from Streptomyces tsukubaensis early in 1984 by Fujisawa Pharmaceutical Co. Ltd. Clinically, tacrolimus has been widely used as the second generation of antirejection drug in kidney and liver transplantation since 1989, which displayed potent immunosuppressive activity, high organ survival rate and low incidence of acute rejection.[5],[6] Tacrolimus fast release capsule with the brand name Prograf® was the first approved tacrolimus oral solid dosage form developed by Astel-las Pharma Inc.[7],[8] Although it is highly effective in clinical set up, as a BCS Class II drug with a very narrow therapeutic window, tacrolimus exhibits large intra- and interindividual variability of bioavailability varying from 4% to 89%. Thus, the blood concentration of tacrolimus must be individually monitored to ensure its efficacy and safety. To obtain suitable blood tacrolimus level and improve its oral bioavailability and patient compliance, tacrolimus-sustained-release dosage forms have been developed in recent years.[6],[9]

According to the recent studies, it has been observed that overall extended release tacrolimus (Advagraf©, Astellas Pharma Canada Inc.; Astagraf XL©, Astellas Pharma US) has a very similar safety and efficacy profile to tacrolimus-BID (Prograf©; Astellas Pharma Europe Ltd, Staines, United Kingdom; referred to as tacrolimus-BID).[7],[8],[9] Since the currently available extended release tacrolimus formulation Astagraf XL© has very similar safety and efficacy profile to immediate release tacrolimus formulations. This present research has explored the new concepts to solve the problems of currently available dosage forms.

The present study describes the preparation of microbeads of tacrolimus using ionic gelation with chitosan, xanthan gum, and sodium alginate as polymers, and calcium chloride as a counter ion. It also includes the evaluation of various parameters used in measuring release rate of tacrolimus microbeads.

 Materials and Methods



Materials

Tacrolimus was obtained from Concord Biotech Ltd, Ahmadabad, India. Sodium alginate, xanthan gum, and calcium chloride were purchased from Muscat, Oman. All other reagents and solvents used were of analytical grade.

Methods

Ionotropic gelation technique was used for the preparation of microbeads dosage form.[10],[11],[12]

Preparation of microbeads

Preparation of placebo microbeads

Three placebo batches (M1, M2, and M3) of microbeads were prepared using sodium alginate polymer with the calcium chloride as a counter ion. About 25 ml of different concentrations of aqueous solutions of sodium alginate (2%, 1.5%, and 1% w/v) were added drop wise into 50 ml of aqueous calcium chloride solution, resulting in instantaneous gelation to form beads. The solution was filtered after stirring for15 minutes and wet form of beads were collected. The prepared microbeads were washed with water and dried at room temperature for 24 hours. Three sets of placebo microbeads were prepared to select the suitable concentration of polymer solution based on the yield of microbeads. The formulae are summarized in [Table 1].{Table 1}

Preparation of microbeads using various polymers namely alginate and chitosan and a drug

The study on effect of different concentrations of chitosan as a release modifier was carried out. Three batches (CM1, CM2, and CM3) of microbeads were prepared with same concentration of drug tacrolimus (5 mg) and by using sodium alginate and chitosan as coating polymers. To 25 ml of deionized water, different percentages of sodium alginate (2%, 1.5%, and 1%) were added in each batch and stirred with magnetic stirrer to get uniform dispersions. About 5 mg of tacrolimus and 1 ml acetonitrile (for good solubility of tacrolimus in the solution) were added. After 10 minutes of stirring, different concentrations of chitosan (1%, 1.5%, and 2%) were added to the solution. The mixture of the drug and polymer dispersion was added drop wise into 50 ml of aqueous calcium chloride solution, resulting in instantaneous gelation to form beads. The solution was filtered after stirring for 1 hour and the wet form of beads were collected. The formed microbeads were washed with water and dried at room temperature for 24 hours. The composition of formulations is summarized in [Table 2].{Table 2}

Preparation of alginate–xanthan gum microbeads containing drug

The study on effect of different concentrations of xanthan gum (1%, 1.5%, and 2%) as a release modifier was carried out. Three batches of microbeads (XGM1, XGM2, and XGM3) were prepared with same concentration of drug (5 mg) tacrolimus and by using sodium alginate and xanthan gum as coating polymers. To 25 ml of deionized water, different percentages (2%, 1.5%, and 1%)of sodium alginate were added to each batch and stirred with magnetic stirrer to get uniform dispersion and 5 mg of tacrolimus and 1 ml acetonitrile (for good solubility of tacrolimus in the solution) were added. After 10 minutes of stirring, different concentrations of xanthan gum (1%, 1.5%, and 2%) were added to the solution. The mixture of the drug and polymer dispersion was added drop wise into 50 ml of aqueous calcium chloride solution, resulting in instantaneous gelation to form beads. After stirring for 1 hour, the solution was filtered and the wet form of beads was collected. The formed microbeads were washed with water and dried at room temperature for 24 hours. The composition of formulations is summarized in [Table 2].

Optimization of microbeads formulations

The 22 factorial designs were applied to evaluate the relationship between the independent variables and their responses.[13],[14],[15],[16],[17] Two variables and two responses were involved in the experimental design. Percentage yield, % entrapment efficiency, particle size, and drug release (dependent response factor variables) were measured. All eight batches of microbeads were prepared with same concentration of drug and two independent variables were the concentrations of calcium chloride (factor X) and stirring time (factor Y). They were classified as low and high, and their values are summarized in [Table 3],[Table 4],[Table 5]. Based on the evaluation parameters, CM1 and XGM1 batches were selected for further preparation of four batches (CM1a, CM1b, CM1c, and CM1d) of chitosan microbeads and another four batches (XGM 1a, XGM 1b, XGM 1c, and XGM 1d) of xanthan gum microbeads.{Table 3}{Table 4}{Table 5}

Evaluation of microbeads

Particle size measurement

All the formulations were subjected to particle size analysis. Morphology and size characteristics of the microbeads were analyzed using scanning electron microscopy.[18]

The percentage yield

The percentage yields of formulated microbeads of various batches were calculated as per the formula[19],[20] mentioned below:

[INLINE:1]

Determination of encapsulation efficiency

Accurately weighed microbeads equivalent to 100 mg were suspended in 100 ml of simulated intestinal fluid of pH 6.8 and kept for 24 hours. Next day, it was stirred for 10 minutes and filtered. After suitable dissolution, the drug content in the filtrate was analyzed spectrophotometrically at 297 nm using ultraviolet (UV) spectrophotometer. Finally, drug encapsulation efficiency was calculated.[21]

[INLINE:2]

The results of percentage yield and drug entrapment efficiency are summarized in [Table 6].{Table 6}

In vitro release studies

The in vitro release rate studies were performed in phosphate buffer (pH 6.8) media over a period of 24 hours. About 100 mg prepared microbeads were added to the dissolution medium. The percentage of drug released after each time interval is depicted in [Table 7] and [Table 10].[21]{Table 7}

The procedure was followed for three batches of chitosan microbeads initially (CM1, CM2, and CM3). From that CM1 was selected for optimization study and as per factorial design method, four other batches of chitosan microbeads (CM1a, CM1b, CM1c, and CM1d) were evaluated by the same procedure of in vitro dissolution study.

The same procedure was followed for three batches (XGM1, XGM2, and XGM3) of xanthan gum microbeads initially and XGM1 batch was selected for optimization study. As per the factorial design method, four other batches of chitosan microbeads (XGM1a, XGM1b, XGM1c, and XGM1d) were evaluated by the same procedure of in vitro dissolution study.

 Results



Evaluation of placebo and drug-loaded microbeads

The results of the percentage yield and the percentage of drug entrapment efficiency are summarized in [Table 6].

Dissolution studies

Dissolution profile of tacrolimus-loaded microbeads using chitosan polymer and xanthan gum in varying concentrations is summarized in [Table 7].

Release kinetic study of drug-loaded batches

The R2 value of different plots is summarized in [Table 8].{Table 8}

Evaluation of Factorial design batches

The percentage yield and drug entrapment efficacy (CM1 and XGM1 batches) are summarized in [Table 9].{Table 9}

Dissolution studies of optimized batches

Dissolution profile of optimization batches of tacrolimus-loaded microbeads using chitosan polymer in varying concentrations is summarized in [Table 10].{Table 10}

Release kinetic studies on different batches

The R2 values of different plots are summarized in [Table 11].{Table 11}

 Discussion



Drug excipients compatibility studies

Drug and polymers interaction studies were performed using Fourier-transform infrared spectroscopy (FTIR). Infrared studies at wavelength from 4000/cm to 400/cm showed that there was neither major shift nor any loss of functional peak in the spectra of drug and polymers. Hence, the drug tacrolimus was found compatible with polymers such as sodium alginate, chitosan, and xanthan gum.

Evaluation of placebo and drug-loaded microbeads

According to [Table 6], the percentage practical yield of placebo microbeads was found in the range of 68% to 78%. Batch M1 shows highest percentage yield of 78% which indicated that the highest yield is due to increase in Na alginate concentration and same concentration of CaCl2. Hence, batch M1 formula was selected for further formulation development process.

The percentage yield of tacrolimus microbeads using polymer chitosan batches was found in the range of 67% to 75%. The maximum percentage yield was found to be 75% for batch CM1 formulation, as summarized in [Table 6]. The amount of drug entrapped was found within the range of 76.43% to 78.82%, as summarized in [Table 6]. Maximum drug entrapment efficacy was found to be 78.82% for CM1 batch.

The percentage yield of tacrolimus microbeads using polymer xanthan gum batches was observed in range of 69% to 76%. Maximum percentage yield was 76% for XGM1 formulation, as mentioned in [Table 6]. The practical yield in percentage was found to increase with increase in concentration of the polymer added to the formulation. The drug entrapment efficacy was found within 75.12% to 77.35%, as summarized in [Table 6]. Maximum drug entrapment efficacy was found to be 77.35% for XGM1 batch [Figure 1].{Figure 1}

Dissolution studies

The results of dissolution rate studies of tacrolimus-loaded microbeads using chitosan polymer and xanthan gum in varying concentrations are shown in [Table 7].

Microbeads CM1 to CM3 showed release in the range of 96 ± 0.9% to 93.6 ± 1.02% and microbeads XGM1 to XGM3 showed release in the range of 95.06 ± 1.09% to 92.6 ± 0.72%.

Release kinetic study of drug-loaded batches

According to [Table 8], the drug-release kinetics followed a complex order drug release. The correlation coefficient (R2 value = 0.966) indicated zero-order-release mechanism and this mechanism of drug release was followed by super case II transport.

The formulations CM1 and XGM1 batch containing 2% of Na alginate and 1% of chitosan polymer and 1% of coating polymer xanthan gum, respectively, showed a slow release of 93.6 ± 1.02% for formulations CM1 and 92.6 ± 0.72% for formulation XGM1.

It was found that tacrolimus Na alginate microbeads coated with xanthan gum (XGM1) showed delayed drug release compared to one prepared with chitosan polymer (CM1). Hence, the CM1 and XGM1 batches were selected for further optimization by factorial design method.

Evaluation of factorial design batches

As summarized in [Table 9], the percentage yield of CM1a, CM1b, CM1c, and CM1d batches was found to be in range of 65.96 ± 0.12% to 74.80 ± 0.08%. CM1b batch showed higher yield of 74.80 ± 0.08%. Maximum drug entrapment efficacy was found in CM1d batch, that is, 89.02 ± 0.04%.

The percentage yield of XGM1a, XGM1b, XGM1c, and XGM1d batches was found in the range of 70.59 ± 0.04% to 77.88 ± 0.12% which had been shown in [Table 9]. F4c batch showed highest percent yield of 77.88 ± 0.12. Maximum drug entrapment efficacy was found in XGM1d batch, that is, 84.87 ± 0.1%.

Dissolution studies of optimized batches

The in vitro drug release studies of microbeads (CM1a–CM1d) were observed in the range of 90.54 ± 0.5% to 93.87 ± 0.82%, as summarized in [Table 10].

The formulation CM1d containing 2% of sodium alginate and 1% coating polymer chitosan and 4% of CaCl2 with higher 1 hour stirring time showed a 90.54 ± 1.02% release of drug. The formulation XGM1d containing 2% of sodium alginate, 1% of coating polymer xanthan gum, and 4% of CaCl2 with higher 1 hour stirring time showed a 89.86 ± 0.34% release. CM1d and XGM1d batches were selected for study by scanning electron microscopy.

Release kinetic study of optimized batches

The correlation coefficient (R2 value) indicates zero-order-release mechanism and this mechanism of drug release was followed by super case II transport which is explained in the [Table 11].

Scanning Electron Microscopy results (SEM)

Optimized microbeads formulations namely CM1d and XGM1d batches (Sodium alginate microbeads coated with chitosan and Xanthan gum respectively) were evaluated for shape and size using SEM.

According to SEM analysis, drug-loaded microbeads were found to be discrete, large, and spherical, free flowing, monolithic matrix and had smooth surfaces.

The average size of microbeads for two batches i.e. CM1d and XGM1d were found to be 1.14 mm to 1.50 mm which were within the range.

 Conclusion



Sodium alginate-based microbeads comprising of tacrolimus with two different polymers namely chitosan and xanthan gum were successfully formulated by ionotropic gelation method. The preformulation studies such as melting point, solubility, and UV analysis of tacrolimus complied with IP standards. The compatibility studies carried out by FTIR spectroscopic studies revealed that there was no significant interaction between drug and polymers. The polymer–drug ratios showed an influence on the particle size, drug entrapment efficiency, and percentage of drug release. The kinetic studies suggested that the drug released by zero-order mechanism followed by super case II transport providing promising drug delivery in organ transplant area.

Xanthan gum is soluble in water and confers high viscosities at low concentrations. The molecular weight of xanthan gum is more than the chitosan polymer. Xanthan gum has good drug retarding ability, prevent initial burst release, inertness, and biocompatibility. Due to that compared to chitosan microbeads, the sustained release action was more in xanthan gum microbeads. Both chitosan microbeads and xanthan gum microbeads fitted into zero-order-release kinetic models.

Therefore, it was concluded that the tacrolimus-loaded microbeads using xanthan gum polymer (batch XGM1d) are more successful pharmaceutical dosage forms compared to tacrolimus-loaded microbeads using chitosan polymer (batch CM1d). A potential drug delivery system with improved oral bioavailability of the drug was thus developed.

The present invention is related to a microbead capsule formulation containing a macrolide compound and having an ability of sustained release, for use in the medical field. The outcome of the research was the development of a novel capsular system for the selected drug. This system was developed to have a modified (sustained) release pattern to provide posttransplant care for people those who are using tacrolimus medication throughout their life. In addition, this new invention of capsular system will help to provide reasonable improved safety and efficacy profile for prophylaxis of organ rejection.

Financial support and sponsorship

This research work had been funded by The Research Council, Oman.

Conflicts of interest

There are no conflicts of interest.

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