Formulation and evaluation of extended release hard capsules of Furosemide

 

Zain Mhanna¹*, Dr. Wehad Ibrahim², Dr. Tamim Hammad³

¹Master Student, Pharmaceutics and Pharmaceutical Technology Department, Faculty of Pharmacy, Tishreen University, Syria. Syria-Lattakia                    

²Doctor in Pharmaceutics and Pharmaceutical Technology Department, Faculty of Pharmacy, Tishreen University, Syria. Syria-Lattakia                    

³Assistant Professor in Pharmaceutics and Pharmaceutical Technology Department, Faculty of Pharmacy, Tishreen University, Syria. Syria-Lattakia                    

 

ABSTRACT:

The aim of the present study is to prepare extended hard capsules of Furosemide using Eudragit RL, Eudragit RS and Ethyl cellulose individually in different ratios (8, 12, and 15%) and different particle size of granules. The granules were prepared by wet granulation and then filled into capsules. The influence of different concentrations of polymer, type of polymer and granules size was studied. The prepared capsules assessed for their physicochemical properties and in-vitro drug release studies. The in vitro release data show that Ethyl cellulose has more retardation than Eudragits, and Eudragit RS retards drug release more than Eudragit RL does. In addition, higher concentration of polymer enhances the retardation better than lower concentration, and increasing the particle size of granules can alter the release of drug.

 

INTRODUCTION:

Most traditional drugs require multiple doses in order to achieve an active plasma drug concentration, and this might increase the risk of dose fluctuation. For that, the need of extended release formulation becomes more important. ⁽¹⁾

 

Extended release dosage forms help to control plasma drug levels, reduce frequency of drug dosing and provide constant delivery. ⁽²⁾

 

Different Insoluble polymers have been used in this study: Eudragit RL, Eudragit RS, and Ethyl cellulose. Eudragit RL, RS are copolymers of acrylic and methacrylic esters with different permeability depending on functional ionized or neutral groups, they are commonly used to form water-insoluble film coats for sustained-release products.  Eudragit RL films are more permeable than those of Eudragit RS are, and films of varying permeability can be obtained by mixing the two types together. While, Ethyl cellulose is a hydrophobic polymer used in preparation of extended release formulations. ⁽³⁾

 

Furosemide is a potent diuretic with a rapid action which is used in the treatment of edema associated with heart failure, hypertension, either alone or with other antihypertensive. It inhibits the reabsorption of electrolytes primarily in the thick ascending limb of the loop of Henle and in the distal renal tubules. It may also have a direct effect in the proximal tubules. Excretion of sodium, potassium, calcium, and chloride ions is increased and water excretion enhanced. It has no clinically significant effect on carbonic anhydrase. Furosemide’s effects are evident within 30 minutes to 1 hour after an oral dose, peak at 1 to 2 hours, and last for about 4 to 6 hours. In the treatment of edema, the usual initial oral dose is 40 mg once daily, adjusted as necessary according to response. Some patients may need doses of 80 mg or more daily given as one or two doses daily, or intermittently. Severe cases may require gradual titration of the Furosemide dosage up to 600 mg daily. In the treatment of hypertension, Furosemide is given in oral doses of 40 to 80 mg daily, either alone, or with other antihypertensives. ⁽⁴⁾

 

There are many limitations about using Furosemide, which include low and highly variable bioavailability, frequent hypokalemia, reduction in glomerular filtration rate (GFR) and very short duration of action (approximately 3 hours) which permits the kidney to regain much of the salt and water lost in between doses. Therefore, it is not surprising that many patients become furosemide resistant (i.e. retain fluid despite furosemide therapy).^(5),(6) To address these manifest deficiencies of furosemide therapy, it is important to develop an extended release formulation of Furosemide. On the other hand, extended release system is necessary for Furosemide delivery in order to increase its bioavailability, eliminate side effects, increase the effectiveness of drug and enhance patients' compliance.

 

The major focus of the present research is to design  extended release dosage form of Furosemide in the form of hard capsules and study the effects of using different ratios of varies polymers on the extended drug release from these capsules.

 

MATERIALS AND METHODS:

Materials

Furosemide was purchased from Sigma-Aldrich Company, Germany. Eu (RL), Eu (RS), EC were purchased from Röhm Pharma Polymers Co., Germany. All other materials are High quality chemistry products.

 

Methods

Preparing of granules

Different granules formulations were prepared to be filled into capsules as shown in tablet (1):  

 

Different formulations of Furosemide were prepared by wet granulation technique using isopropyl alcohol as a granulating agent. Lactose was used as a diluent and mixture of talc and magnesium stearate was used as lubricant. Granules of Furosemide and polymer (Eudragit RS or Eudragit RL or ethyl cellulose) were prepared. The powders were blended and granulated with isopropyl alcohol. The obtained granules were dried, sieved and separated into three different ranges based on the particle size (tab.1). The granules retained were mixed with lubricants (talc 2% and magnesium stearate 0.5%) and evaluated for several tests.

 

 

Table 1: composition of Furosemide formulae

 

 

Physical characterization of capsules

Uniformity of weight

The test for uniformity of weight capsules was performed using British pharmacopoeia 7th edition. Twenty capsules were randomly selected from each formula and individually weighed using an electronic balance (Precisa XB 220 A/ Germany). The average weight and standard deviation of 20 capsules was calculated. The prepared capsules pass the test for Uniformity of weight if not more than (2) of the individual masses deviate from the average mass by more than the percentage deviation (±10%) and none deviates by more than twice that percentage.⁽⁷⁾

 

Uniformity of dosage units:

This test was done to ensure the consistency of dosage units. It was done by "mass variation" depending on British pharmacopoeia-7th edition, appendix xII. 10 capsules were assayed individually and the acceptance value was calculated using the formulae: 

 

AV= |M-X| +KS

 

where: X: mean of individual estimated contents of the dosage units tested where:

 

xi = wi x A/

 

A = content of active substance (percentage of label claim) obtained using an appropriate analytical method (assay)

 = mean of individual masses of the units used in the assay

w₁, w₂... w_n = individual masses of the dosage units tested

M= the Reference value 

 

The requirements for dosage uniformity are met if the acceptance value of the first 10 dosage units is less than or equal to L1. If the acceptance value is greater than L1, test the next 20 dosage units and calculate the acceptance value. The requirements are met if the final acceptance value of the 30 dosage units is less than or equal to L1 and no individual content of the dosage unit is less than (1 - L2 × 0.01)M or more than (1 + L2 × 0.01)M in calculation of acceptance value under content uniformity or under mass variation. Unless otherwise specified, L1 is 15.0 and L2 is 25.0.⁽⁷⁾

 

In-vitro release studies

In-vitro dissolution study was carried out using Apparatus II (British Pharmacopoeia 7th edition, Appendix XII B,) in 900 ml 0.1 N HCl for two hours, followed by replacement with 900 ml phosphate buffer (pH 5.8) for the next 10 hours till the end of the 12 hours at a temperature of 37±0.5ºC at a rotation speed of 50 rpm (Erweka DT 600 dissolution tester; Germany).The experiments were done on 6 individual capsules and the mean values calculated. Aliquots of 10 ml were withdrawn from the release medium through micronics filter at predetermined time intervals and replaced by 10 ml of fresh dissolution medium. The amount of Furosemide released was measured using UV spectrophotometer (JascoV-530/ VIS-spectrophotometer/ Japan) at λ value of (277) nm and  cumulative  percentage  drug  release was calculated.⁽⁷⁾

 

Kinetics of drug release:

The dissolution data obtained were fitted into various kinetic models, namely: zero order, first order, Higuchi and Korsmeyer-Peppas. This was to determine the mechanism of drug release. Higuchi model ⁽⁸⁾ represents the relationship between quantity of drug released and the square root of time:                          

 

Q=K t^1/2                       (1)  

 

The Higuchi release constant k and R² values were extracted from the graph.  For  zero  order,  from  the  equation:  C=K₀ t,  drug  concentration  was  plotted  against  time.  The zero order rate constant k₀ and the regression line (R²) values were also extracted from the graph. For First order release kinetics, Log cumulative % drug remaining was plotted against time. The first order rate constant k₁ and the regression line value (R²) were extracted from the graph. To  confirm  the  exact  release  mechanism  operational  the  data  were  fitted  according  to  Korsemeyer-Peppa’s equation:  

 

mt/mT = k tⁿ                 (2)

 

Where,  mt/mT  is  fraction  of  drug  released,  k  is  kinetic  constant,  t  is  release  time  and  ‘n’  is  the  diffusional exponent for drug release. This simple empirical equation is used to describe general solute release behavior from controlled release polymer matrices. ⁽⁹⁾

 

RESULTS AND DISCUSSION:

Physicochemical Properties of prepared capsules

The results of weight variation and acceptance values are shown in table (2).

 

Weight variation of capsules was found to vary  between 0.1931 g to 0.2063 g. individual weights are within limits set with reference to the  average content of the sample (±10%). consequently, capsules prepared in this study comply with the test for uniformity of weight test.

 

AV value of all formulae is less than 15.0 %. Consequently, capsules prepared in this study comply with the test for uniformity of dosage units

Table 2: Weight variation and acceptance values results of prepared formulae

 

In-vitro dissolution studies shows the effect of three factors (type of polymer, ratio of polymer and granule size) on drug release rate:

 

Type of polymer:

Figs. (1), (2), (3), (4), (5), (6) demonstrate the effect of type of polymer:

 

Fig. (1) Comparative Dissolution Profiles for formulae (F1, F2, F3)

Polymer con. = 12%; (0.5-1 mm)

 

Fig. (2) Comparative Dissolution Profiles for formulae (F4, F5, F6)

Polymer con. = 8%; (1-1.6 mm)

 

Fig. (3) Comparative Dissolution Profiles for formulae (F7, F8, F9)

Polymer con. =12%; (1-1.6 mm)

 

Fig. (4) Comparative Dissolution Profiles for formulae (F10, F11, F12)

Polymer con. =15%; (1-1.6 mm)

 

Fig. (5) Comparative Dissolution Profiles for formulae (F13, F14, F15)

Polymer con. =12%; (2-2.5 mm)

 

Fig. (6) Comparative Dissolution Profiles for formulae (F16, F17, F18)

Polymer con. =15%; (2-2.5 mm)

Based upon these dissolution profiles, the formulations containing Eu (RL): (F1, F4, F7, F10, F13, F16) have the highest release rate. Then, formulation containing Eu (RS): (F2, F5, F8, F11, F14, F17) and then, formulation containing EC: (F3, F6, F9, F12, F15, F18). Additionally, the release from capsules, which contain EC, was found to be slower and more controlled.

 

Eu (RL) contains quarter ammonium groups more than Eu (RS). Thus, Eu (RL) is more permeable to water than Eu (RS). Consequently, Eu (RS) alters drug release more than Eu (RL) does, which complies with that stated in the literatures. ⁽¹⁰⁾

 

On the other hand, EC alters drug release due to its hydrophobic nature, which causes matrix to be less permeability to the solvent. ⁽¹¹⁾

 

In addition to that, It was observed that the initial percent release for the first three hours was quite high (30-71 %) for all the formulations. However, in the later stages the release was found to be slower and more controlled in the capsules with higher proportion of the polymer. On the other hand, formulations containing 8% either of Eudragit released between 65 % and 71% of drug at first three hours. This may be due to initial burst effect caused by surface erosion or disaggregation of matrix granules prior to gel layer formation around the granules. However, formulations containing 12% and 15% either of the Eudragit  released only between 30% and 43% of drug at the first three hours and not less than 54.53% in 12 hours.

 

In addition, the formulations that contain 8% of EC released about 63% of drug for the first three hours, while other formulations that contain 12% and 15% of EC released only about 30% to 40% of drug. When Ethyl cellulose, a water-insoluble polymer, exposed to water, it swells and retards drug release. Thus, it displays initial surface erosion, which is responsible for the initial fast release. ⁽¹²⁾

 

Concentration of polymer

Figs. (7), (8), (9), (10), (11), (12) demonstrate the effect of polymers´ concentration on drug release:

 

Fig. (7) Comparative Dissolution Profiles for formulae (F4, F7, F10). ; EU (RL) ; ( 1-1.6 mm)

 

Fig. (8) Comparative Dissolution Profiles for formulae (F13, F16); Eu (RL); (2-2.5 mm)

 

According to figs. (7), (8): the formulations F4 (RL 8%), F7 (RL 12%) and F10 (RL 15%) release respectively (94.85 %), (80.55%) and (78.27%) of Furosemide after 12 hrs. indicating reduced rate and extent of drug release with higher concentration of polymer. While, the formulations F13 (RL 12%) and F16 (RL 15%) release respectively (66.84 %) and (57.64%) of Furosemide after 12 hrs. indicating reduced rate and extent of drug release with higher concentration of Eu(RL).

 

These results comply with another study which has been done by two researchers Khalil YI. and Hussain AH. the aim of their research is to prepare a solid sustained release dosage form of Pentoxifylline using Eudragit RL and Eudragit RS; the study shows that using more high concentration of polymer causes drug matrix to be more retarded. ⁽¹³⁾

 

Fig. (9) Comparative Dissolution Profiles for formulae (F5, F8, F11); EU (RS) ;( 1-1.6 mm)

 

Fig. (10) Comparative Dissolution Profiles for formulae (F14, F17); Eu (RS); (2-2.5 mm)

 

According to figs. (9),(10): the formulations  F5(RS 8%) , F8(RS 12%) and F11(RS 15%)  release respectively (88.07% ),(79.38%) and (74.99%) of Furosemide after 12 hrs. indicating reduced rate and extent of drug release with higher concentration of polymer. While, the formulations F14 (RS 12%) and F17 (RS 15%) release respectively (64.90%),(54.35%) of Furosemide after 12 hrs. indicating reduced rate and extent of drug release with higher concentration of  Eu(RS) .

 

These results comply with another study, which has been done by two researchers Hussein AA. and Ghareeb MM.  In which different formulations of meloxicam tablets were prepared using different ratios of carnauba wax, ethyl cellulose and Eudragit RS; The results indicated that increasing the concentration of polymer tend to decrease the drug release significantly ⁽¹⁴⁾

 

Fig. (11) Comparative Dissolution Profiles for formulae (F6, F9, F12); EC ;( 1-1.6 mm)

 

According to figs. (11),(12): the formulations  F6(EC 8%), F9(EC 12%) and F12(EC 15%)  release respectively (83.60%), (77.56%) and (72,67%) of Furosemide after 12 h. indicating reduced rate and extent of drug release with higher concentration of polymer. while, the formulation  F15(EC 12%) and F18(EC 15%)  release respectively (62.35%), (52.60%) of Furosemide after 12 h. indicating reduced rate and extent of drug release with higher concentration of EC.

 

Fig. (12) Comparative Dissolution Profiles for formulae (F15, F18); EC; (2-2.5 mm)

 

These results comply with another study, which has been done by Chithaluru K. and his colleagues about preparing twice-daily sustained release matrix tablets of Losartan potassium using Eudragit RLPO, RSPO and Ethyl cellulose individually and in combination of above polymer; the study shows less amount of drug has been released from formulations containing high concentration of EC.⁽¹⁵⁾

 

To conclude, the release of the drug from the capsules extended as the polymer proportion increased. This is due to decreased penetration of the solvent molecules in the presence of hydrophobic polymer, leading to reduced diffusion of the drug from matrix system. The pore network in hydrophobic polymers becomes more tortuous resulting in slower drug release.

 

Particle size of drug granules:

Figs. (13, 14, 15, 16, 17, 18) shows the effect of particle size of Furosemide on drug release.

 

Fig. (13) Comparative Dissolution Profiles for formulae (F1, F7, F13); (RL 12%)

 

Fig. (14) Comparative Dissolution Profiles for formulae (F2, F8, F14); (RS 12%)

 

Fig. (15) Comparative Dissolution Profiles for formulae (F3, F9, F15); (EC 12%)

 

Fig. (16) Comparative Dissolution Profiles for formulae (F10, F16); (RL 15%)

 

Fig. (17) Comparative Dissolution Profiles for formulae (F11, F17); (RS 15%)

 

Fig. (18) Comparative Dissolution Profiles for formulae (F12, F18); (EC 15%)

 

According to in-vitro release studies, the formulations that have particle size in range (0.5-1 mm) have the highest release when compared to all other formulations. While the formulations that have particles size in range (2-2.5 mm) have the lowest release profile.

As a result, increasing the particle size of granules reduces the release rate of drug.

When the particle size is decreased, the larger surface area of the drug allows the increase in the surface area to volume ratio thus increasing the surface area available for solvation. ⁽¹⁶⁾

 

Kinetics of drug release:

Table (3) shows the various release kinetic parameters of the formulae having different degrees of fit, with some having better fit than others have.

 

Table (3): in-vitro dissolution parameters of Furosemide capsules  

Formula	R2 Zero order	R2 First order	R2 Higuchi	R2 Korsmyere-peppas	n Korsmyere-peppas
F1	0.8523	0.9652	0.9495	0.9562	0.8217
F2	0.8631	0.9648	0.9545	0.9634	0.7848
F3	0.8869	0.9657	0.9653	0.9727	0.757
F4	0.6923	0.8978	0.8354	0.8883	0.7307
F5	0.6921	0.8552	0.8306	0.8713	0.8275
F6	07033	0.8475	0.8371	0.8677	0.8136
F7	0.8511	0.8475	0.9478	0.9641	0.8163
F8	0.8583	0.9541	0.9542	0.9563	0.8893
F9	0.8802	0.9561	09619	0.971	0.8046
F10	0.9708	0.9465	0.9614	0.9369	0.8212
F11	0.8711	0.9516	0.96	0.9632	0.8667
F12	0.8708	0.9465	0.9614	0.9396	0.9007
F13	0.7622	0.8551	0.9056	0.8617	0.8503
F14	0.8283	0.8855	0.9246	0.945	0.5606
F15	0.879	0.9241	0.9456	0.9493	0.6098
F16	0.7777	0.8246	0.8959	0.9333	0.6836
F17	0.8335	0.8758	0.928	0.9473	0.6567
F18	0.7987	0.8378	0.9073	0.9451	0.7209

 

The release kinetics of F4, F5 and F6 could not be explained with the above release models as evidenced by their very poor fits. F1, F2 and F3 released drug by Higuchi and first order release kinetics, but the most predominant release mechanism was First order. This may back to the small surface area of drug that causes fast drug diffusion from the matrix. On the other hand, F7, F8, F9, F11, F12, F13, F14, F15, F16, F17 and F18 had Higuchi as the most predominant release kinetic model. While F10 showed a combination of Higuchi, first order and zero order kinetics, but the most predominant release mechanism was zero order. Zero order release is the ideal in controlled drug release and has been reported not to be common with matrix systems; this being attributed to diffusional path length.⁽¹⁷⁾

 

In addition, all the formulae gave Korsemeyer-Peppas ‘n’ values between 0.45 and 0.89, which indicates a super case Ι release except F12 gave values above 0.89 and this indicates a super case ΙΙ.⁽¹⁸⁾ 

 

The operation of more than one release mechanism is very possible as revealed by some of the formulae. In all formulae, Higuchi release kinetics implies that there was a progressive diffusion controlled release process. Secondly, drug release was also taking place independent of time and concentration of drug (Zero order) as shown in F10. In addition, drug concentration-dependent release (First order) in many formulae was also going on. All these release mechanisms may have taken place one after the other or simultaneously. If there is more than one opening on the surface of the capsule this may lead to release mechanisms taking place simultaneously (sometimes at the same or different rate) or consecutively.

 

CONCLUSION AND RECOMMENDATION:

In this present research, extended released hard capsules of Furosemide have been prepared using different types of polymer (EU RL, EU RS and EC) with different ratios (8,12 and 15%) and different particle size of granules (0.5-2.5 mm) by wet granulation. The results shows that the release of Furosemide decreases as the concentration of polymer increases. On the other hand, it was indicated that EC is the most retarding polymer, then Eu (RS) and then Eu (RL). Besides, increasing the particle size of granules alters the release rate of drug. It is recommended for next researches to study extended release hard capsules of Furosemide In-vivo, and study other agents that affect on extended drug release from hard capsules of Furosemide.

 

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Received on 14.11.2015          Modified on 21.11.2015

Accepted on 05.12.2015        © RJPT All right reserved