Formulation and In Vitro-In Vivo Evaluation of Alfuzosin Hydrochloride Floating Matrix Tablets

Rahul K Godge, Stephen L Fernandes, Syed N Lateef, Abhijeet N Merekar and Prakash N Kendre*

Sanjivani College of Pharmaceutical Education and Research, Sahajanandnagar Kopargaon- 423603, Ahmednagar, (M.S.)

ABSTRACT

The aim of the study was to develop and physicochemically characterize single unit controlled delivery system of alfuzosin hydrochloride and was formulated as floating matrix tablet by direct compression method using gas generating agent (sodium bicarbonate) and various viscosity grades of hydrophilic polymers (HPMC K15M, K4M; HPC and Carbopol 934P). Formulation was optimized on the basis of buoyancy and in vitro drug release profile. Also tablets were tested for various tests like hardness, thickness, weight variation, friability, swelling index and erosion index. The tablets swelled and eroded upon contact with release medium (0.1 N HCl) at 37 ⁰C. The release rate could efficiently be modified by varying the matrix forming polymer, the use of polymer blends and the addition of water soluble or water insoluble fillers (such as dicalcium phosphate, lactose or mannitol).The physical blends were analyzed for FT-IR,DSC study and showed no incompatibility. Also SEM study was used to visualize the effect of dissolution medium on matrix tablet surface. Fitting the in-vitro drug release data to Korsmeyer equation indicated that diffusion along with erosion could be the mechanism of drug release.

KEYWORDS: Alfuzosin hydrochloride, Carbapol, HPMC, Floating matrix tablets, scanning electron microscopy, swelling index.

INTRODUCTION

The recent research studies and various literatures reveals that pharmaceutical dosage forms exhibiting good in vitro floating behavior show prolonged gastric residence in vivo (Ichikawa et al., 1991; Kawashima et al., 1991)².e oral route is the route most often used for administration of drugs. Tablets are the most popular oral formulations available in the market and are preferred by patients and physicians alike. In long-term therapy for the treatment of chronic disease conditions, conventional formulations are required to be administered in multiple doses and therefore have several disadvantages⁴.

The real issue in the development of oral controlled release dosage form is not just to prolong the delivery of drugs for more than 12 hrs but also to prolong the presence of dosage forms in the stomach or somewhere in the upper small intestine. Dosage forms with prolonged gastric residence time (GRT), i.e. gastro remaining or gastro retentive drug delivery system (GRDDS) will bring about new and important therapeutic options. For instance, these will significantly extend the period of time over which drugs may be released, and thus prolong dosing intervals and increase patient compliance beyond the compliance level of existing controlled release dosage forms. The effects of simultaneous presence of food and of the complex motility of the stomach are difficult to estimate. Obiviously in vivo studies can provide definite proof that prolonged gastric residence is obtained^{7, 14}.

Extended-release dosage forms with prolonged residence times in the stomach are highly desirable for drugs (i) that are locally active in the stomach, (ii) that have an absorption window in the stomach or in the upper small intestine,(iii) that are unstable in the intestinal or colonic environment, and/or (iv) have low solubility at high pH values.

Table 1: Compositions of floating matrix tablet in mg:

Formulation*	HPMC K4M	HPMC K15M	HPMC K100M	HPC	HPMCK4M + Carbapol 934P**	Lactose	Mannitol	DCP
F-1	150	----	----	----	----	----	----	47.5
F-2	----	150	----	----	----	----	----	47.5
F-3	----	----	150	----	----	----	----	47.5
F-4	150	----	----	----	----	47.5	----	----
F-5	150	----	----	----	----	----	47.5	----
F-6	----	----	----	----	150	----	----	47.5
F-7	----	----	----	----	150	47.5	----	----
F-8	----	----	----	----	150	----	47.5	----
F-9	----	----	----	150	----	----	----	47.5
F-10	----	----	----	150	----	47.5	----	----
F-11	----	----	----	150	----	----	47.5	----

*All batches contained 10mg of drug, 15 %sodium bicarbonate, 1 % magnesium stearate and 1 % Aerosil.

** HPMC K4M and Carbopol 934P blend was taken in 3:1 ratio respectively.

Table 3: Floating Lag Time:

Formulation	Floating lag time (min)*
Formulation	pH 1.2	pH 2.0	pH 3.0
F-1	<1.0	<4.0	>4.0
F-2	<1.0	<4.0	>4.0
F-3	<1.0	<4.0	>4.0
F-4	<1.0	<4.0	>4.0
F-5	<1.0	<4.0	>4.0
F-6	>1.0	<4.0	>4.0
F-7	>1.0	<4.0	>4.0
F-8	>1.0	<4.0	>4.0
F-9	<1.0	<4.0	>4.0
F-10	<1.0	<4.0	>4.0
F-11	<1.0	<4.0	>4.0

Each sample was analyzed in triplicate (n = 3)

Fabrication of floating matrix tablets⁶:

Tablets containing alfuzosin hydrochloride as a pure drug were prepared by direct compression method. The respective powders (drug, polymers, and fillers) and optional additives, compositions listed in Table No.1 were blended thoroughly with a mortar and pestle and finally mixed with magnesium stearate and colloidal silicon dioxide as a lubricant and glidant respectively. Tablets of 250 mg each were compressed by using multiple-punch tabletting machine (Cadmach, Ahmedabad) with constant weight, thickness, diameter (10 mm) and hardness ( approximately 5 Kg/cm²unless otherwise stated) using beveled flat-faced punches. Hardness was measured by using Monsanto hardness tester and diameter and thickness was measured by digital vernier caliper. FTIR, DSC analysis of drug, polymer and blend was shown in figure 1 and 2.

Characterization of tablets⁶:

The properties of the compressed matrix tablets, such as hardness, friability, weight variation and content uniformity were determined by using reported procedure. Hardness was measured by using Monsanto hardness tester and friability was measured by Roche friability testing apparatus. Weight variation and uniformity of drug content were performed according to I.P. procedures. Content uniformity was determined by weighing 10 tablets individually. Evaluation parameters or compression properties are shown in table 2.

Floating behavior of the tablet:^{15, 11}

In vitro buoyancy study of the tablets (n=3) was determined using USP (type II) dissolution apparatus containing 900 ml of 0.1 N HCl (pH 1.2 at 37 ⁰C) at 100 rpm.The time (min) taken by the tablet to reach the top from the bottom of the container (floating lag time), and the time for which the tablet constantly floats on the

surface of the medium (duration of floating) was measured. Floating lag time was shown in table 3.

Scanning electron microscopy study:

The samples of the matrix tablets were removed from the dissolution apparatus at predetermined time interval and sectioned through an undisturbed portion of the gel formed at the flat face of the floating matrix tablet. The sample was then positioned on the sample holder so as to present a cross-section of the matrix tablet to the microscope. Samples were coated with gold and visualized under scanning electron microscope (SEM). Results of SEM shown in figure 3.

Determination of swelling and erosion behavior¹³:

The swelling and eroding behavior of matrix tablet was determined, reported by Al-Taani and Tashoush. Matrix tablet was introduced into the dissolution apparatus containing 900 ml of 0.1 N HCl (pH 1.2 at 37 ⁰C) at 100 rpm. The tablets were removed using a small basket and swollen weight of each tablet was determined. To determine matrix erosion, swollen tablets were placed in a vacuum oven at 40 ⁰C and after48 hours tablets were removed and weighed. Swelling (%) and erosion (%) was calculated according to the following formula, where S is the weight of the matrix tablet after swelling; R is the weight of the eroded matrix tablet; and T is the initial weight of the matrix tablet:

Swelling Index = S − T / T

% Erosion = (T – R) / T ×100.

Swelling and erosion behavior was shown in figure 4.

Accelerated stability testing^{17, 16, 18}:

The stability studies were carried out on optimized formulations. The formulations were stored at 40 ± 2⁰C/75 ± 5 % RH (% relative humidity) for one month. After interval of 7, 15 and 30 days samples were withdrawn and retested for drug content, floating lag time and drug and hardness. Accelerated stability study was shown in table 6.

In vitro drug release studies^{6, 12}:

Dissolution tests were conducted in triplicate for all batches in a USP (type-II) dissolution rate test apparatus (type II) The release studies were performed by using 900 ml of 0.1 N HCl (pH 1.2 at 37 ⁰C) at 100 rpm. Five milliliters aliquots were withdrawn at specific time intervals and drug content was determined by UV-visible spectrophotometer (simatzu-1650 PC) at 244 nm. The release studies were conducted in triplicate. Invitro release study was shown in figure 5 and % drug release study was shown in table 4.

Table 4: Average percentage drug release data:

Sr.

No.

Avg. % drug release

F-1

F-2

F-3

F-4

F-5

F-6

F-7

F-8

F-9

F-10

F-11

1 hr

14.52

0.29

15.52

0.29

14.55

0.27

14.60 ±

0.13

15.11

0.54

12.81

0.29

13.01

0.37

14.28

0.65

13.15 ±

0.47

15.58

0.47

13.88 ±

0.46

2 hrs

18.13

0.38

19.13

0.38

19.17

0.41

19.13 ±

0.38

19.83

0.51

15.85

0.26

16.01

0.47

19.28

0.85

16.69 ±

0.51

19.87

0.95

17.81 ±

0.35

4 hrs

30.93

0.34

31.93

0.34

30.95

0.31

30.93 ±

0.34

32.03 ±

0.34

27.28

0.18

26.98

0.57

27.33

0.86

30.15 ±

0.43

31.56

0.66

30.14 ±

0.38

6 hrs

36.48

0.46

34.33

0.46

37.44

0.48

38.48 ±

0.46

39.00 ±

0.34

34.90

0.46

36.30

0.69

32.46

0.77

36.47 ±

0.61

38.92

0.48

37.10 ±

0.48

8 hrs

47.29

0.30

48.01

0.30

48.21

0.32

48.29 ±

0.30

49.09 ±

0.72

41.79

0.06

42.07

0.87

39.88

0.48

46.66 ±

0.43

49.29

± 0.68

46.51 ±

0.43

10 hrs

54.21

0.27

53.23

0.27

52.24

0.29

54.21 ±

0.27

55.68 ±

0.65

46.41

0.04

45.17

0.48

42.11

0.37

54.16 ±

0.27

55.74 ±

0.57

54.82 ±

0.46

12 hrs

63.69

0.13

64.50

0.13

65.65

0.17

61.60 ±

0.13

64.38 ±

0.35

51.11

0.89

53.15

0.52

49.73

0.86

62.43 ±

0.44

65.55 ±

1.85

62.45 ±

0.34

14 hrs

72.43

0.29

73.63

0.29

71.70

0.39

72.73 ±

0.30

73.32 ±

0.30

58.12

0.93

57.23

0.68

59.38

0.75

70.83 ±

0.66

74.00 ±

0.66

72.58 ±

1.00

16 hrs

82.66

0.15

81.56

0.12

83.64

0.17

82.66 ±

0.15

83.20 ±

0.16

66.98

0.44

69.59

0.59

71.63 ±

0.44

80.19 ±

0.97

83.77 ±

1.00

81.20 ±

0.57

18 hrs

94.86

0.69

93.76

0.69

94.81

0.71

94.85 ±

0.69

85.92 ±

0.43

79.63

0.49

81.43

0.63

83.25

0.45

85.80 ±

0.23

86.01 ±

0.35

86.06 ±

0.27

20 hrs

97.13

0.22

97.09

0.49

96.78

0.31

97.05 ±

0.38

96.81 ±

0.32

91.59

0.84

93.12

0.98

93.8

0.69

96.42 ±

0.44

96.52 ±

0.48

96.09 ±

0.20

Each sample was analyzed in triplicate (n = 3).

Kinetic analysis of the dissolution data^{1, 19:}

In order to study the exact mechanism of drug release from the matrix floating tablets, the release data were fitted to zero-order, first-order and higuichi equation. These models fail to explain drug release mechanism due to swelling (upon hydration in contact with dissolution medium) along with gradual erosion of the matrix. Therefore, the dissolution data was also fitted to the well-known exponential equation (Korsmeyer equation), which is often used to describe the drug release behavior from polymeric systems:

Log (M _t / M_{f )} = Log k + n Log t. Kinetic treatment of floating tablet was shown in table 5. here, M_tis the amount of drug release at time t; M_f is the amount of drug release after infinite time’s is a release constant incorporating structural and geometric characteristics of the tablet; and n is the diffusion exponent indicative of the mechanism of the drug release.

In order to make sure the release exponent for different batches of floating matrix tablets, the log value of % drug dissolved was plotted against log time for each batch according to the Equation. Value of n = 0.45 indicates Fickian (Case I) release ;> 0.45 but <0.89 for non-fickian (anomalous) release; and >0.89 indicates super case II type of release. Case II generally refers to the erosion of the polymeric chain and anomalous transport (non-fickian) refers to a combination of both diffusion and erosion controlled-drug release. Mean dissolution time (MDT) was calculated from dissolution data using the following equation (Mockel and Lippold):

MDT = (n / n + 1). k – 1 / n

Where, n = release exponent and

k = release rate constant.

In vivo gastric retention matrix tablet by using gamma scintographytechnique⁹:

The most commonly used radionuclide to correlate gastro intestinal behavior of the dosage forms with pharmacokinetic parameters i.e. correlation of the location of the dosage forms in a certain region of the GI tract to maximum plasma concentration were Technetium – 99 m (Tc – 99) and Indium 111 (In – 111).

Tc – 99 m was the most widely used radionuclide in nuclear medicine. It has a very short half-life of 6 hrs and emits photons but not particulate radiation (β rays harmful to tissues). It is inexpensive and readily available in generator form or commercially as an aqueous solution. Tc – 99 m possesses most of the characteristics of an ideal radionuclide and hence found widespread applications in nuclear and in pharmaceutical formulation development. The level of radioactivity used in Gamma scintigraphy was very low and it gives a radiation dose participating subjects, which was well below the maximum permissible dose. Gamma scintigraphy was safe and always preferred over previous methods like X-rays as gamma scintigraphy gives very little radiation exposure to the participating subjects. Gamma scintograph of formulation was shown in figure 6a, 6b, and 6c.

Figure No.2: DSC analysis of drug, polymers and its physical blend:

DSC spectrum of Alfuzosin hydrochloride (Drug)

DSC spectrum of HPMC

DSC spectrum of drug + HPMC

RESULTS AND DISCUSSION:

(a) DSC spectrum of HPC

DSC spectrum of drug + HPC

DSC spectrum of drug + Carbopol 934 P

FigureNo.3: Scanning Electron Microscopy Study of Floating Matrix Tablets upon contact with 0.1 N HCl:

(a) (b)

(a) SEM Photograph before swelling

( b) SEM Photograph after 2 hours swelling

(c) ( d)

(c) SEM Photograph after 4 hours swelling

(d) SEM Photograph after 12 hours swelling.

Figure4: Swelling and Erosion study

Figure 5: In-vitro release profiles of Alfuzosin hydrochloride:

In the present study, HPMC K4M, K15M, K100M, HPC and Carbopol 934P which are commonly used in hydrophilic matrix drug delivery systems, have been employed to formulate floating sustained release tablets of Alfuzosin hydrochloride. The physical blends of drug and polymers were analyzed for FT-IR (Fourier-Transform Infra Red spectrophotometer), DSC (Differential Scanning Calorimetry) study and shown no incompatibility which is shown in the Figure No.1 and 2 respectively. All the required ingredients were weighed accurately according to the formula given in the Table No.1. Swelling (%) and erosion (%) was calculated given in the Figure No. 4 respectively by placing swollen tablets in a vacuum oven at 40 ⁰C and after 48 hours’ tablets were removed and weighed. The samples of the matrix tablets were removed from the dissolution apparatus at predetermined time interval and sectioned through an undisturbed portion of the gel formed at the flat face of the floating matrix tablet and analyzed by using Scanning electron microscopy shown in the Figure No.3.

Results of buoyancy study given in the Table No.3 reveals that the tablets of all batches had shown good floating properties due to the presence of gas generating agent, sodium bicarbonate, except the tablets with HPMC K4M and Carbopol 934P blend.

Figure No.6-a: Gammascintograph of formulation -1

Figure No.6-b: Gammascintograph of formultation-6

Formulation with carbopol retards the release of the drug because of its cross-linked polymeric nature with high molecular weight (~2 × 106 Da.) and viscosity and when contacted with water it would swell and hold the water inside its microgel network. Evaluated data demonstrates again that the incorporation of Carbopol 934P has negative effect on the floating behavior of the delivery system .This can be explained by the moisture isotherm of Carbopol 943P which illustrates that Carbopol 934P has a much higher moisture absorption curve compared to cellulose based HPMC and HPC. The moisture gain for Carbopol 943P is significantly higher compared to moisture gain of HPMC (55% weight gain for Carbopol 934P verses ~ 33%for HPMC at RH of 95%).This results in a dramatic increase in the density of the GFDDS which in turn, shows a corresponding decrease in the floating capacity of GFDDS. After accelerated stability testing it was found that irrespective of concentration of polymer, these formulations are able to retain their stability for one month.

Figure No.6-c: Gammascintograph of formultation-9

The gastric retention studies of the formulation 1, 6 and 9 were carried out in three healthy human volunteers using the gamma scintography technique. Fasting conditions were maintained for 12 hrs before study. When tested for 6 hrs, the gamma scintigraphy outputs have shown that the tablets maintained matrix integrity, indicating no effect of gastric conditions on the gelling properties of tablets. This effect was identical to In vitro studies. The gamma scintigraphy outputs were shown in Figure No.6-a, 6-b and 6-c.Accelerated stability data (Table No.6) reveals that no significant changes in the formulations.

In the present studies of dissolution given in the Table No.5 formulation of the batches 1,2,3,4 and 5 were shown the release of drug 63.69%, 64.5%, 65.65%, 61.60% and 64.38 at the end of 12 hours and 97.13%, 97.09%, 96.78%, 97.05% and 96.81% of drug at the end of 20 hours, respectively.

Further the result of dissolution studies of formulation batches 4, 6 and 7 composed of HPMC K4M and carbopol 934P combination with different fillers showing release of drug 51.11%, 53.15%, 49.73% at the end of 12 hours and 91.59%, 93.12%, 93.88% at the end of 20 hours, respectively.

In further dissolution studies of formulations 9, 10 and 11 composed of HPC along with different fillers released the drug 62.43%, 65.55% and 62.45% at the end of 12 hours and 96.42%, 96.52 and 96.09% at the end of 20 hours, respectively.

CONCLUSION:

Overall, this study concludes that from all formulations, formulation 1 shown the highest release followed by 2, 3, 4, 5, 9, 10, 11, 6, 7, and 8 at the end of twenty hours. There was not significant difference in all the formulation batches despite different molecular sizes of polymers, the release of the drug was delayed to same extent, except the formulations with Carbopol 934P which was also observed by some other investigators where Carbopol 934P was found to compromise the release and floating property of GFDDS. Also there was no significant difference in the release of the drug with the different types of fillers. Fitting the in-vitro drug release data to Korsmeyer equation indicated that diffusion along with erosion could be the mechanism of drug release.

ACKNOWLEDGEMENT:

The author would like to sincerely gratitude to the New Life Pharmaceuticals, Pune, India.Colorcon Asia Ltd., Goa, India, Dr.Reddy’s Laboratories, Hydrabad, India for providing all requirements for this project work. Also very thankful to all those who have help directly or indirectly to carry out the research work successfully.

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Received on 18.06.2009

Accepted on 22.08.2009

Research Journal of Pharmaceutical Dosage Forms and Technology. 1(2): Sept.-Oct. 2009, 119-125

Formulation	Thickness *	Drug Content (%)*	Friability (%)	Hardness (kg/cm²)*
F-1	2.80± 0.025	98.17 ± 1.5	0.35	5.2 ± 0.8
F-2	2.93 ± 0.03	98.2 ± 1.3	0.35	5.5± 0.1
F-3	2.93± 0.01	96.9 ± 1.9	0.39	5.5 ± 0.1
F-4	2.84 ± 0.03	98.3 ± 0 .8	0.43	5.5 ± 0.1
F-5	2.85 ± 0.04	98.4 ± 1.1	0.76	5.5 ± 0.2
F-6	2.90 ± 0.0264	97.04 ± 1.2	0.35	5.9 ± 0.3
F-7	2.96 ± 0.025	98.01 ± 1.6	0.27	5.4 ± 0.6
F-8	2.90 ± 0.0173	97.03 ± 1.3	0.43	5.5 ± 0.1
F-9	2.92 ±0.0152	98.97 ± 1.3	0.35	5.5 ± 0.3
F-10	2.92 ± 0.0264	98.10 ± 1.7	0.35	5.5 ± 0.4
F-11	2.90 ±.0264	98.34 ± 1.09	0.19	5.8 ± 0.3