INTRODUCTION:

Pulsatile drug delivery technologies are most widely used to target the drug as per the Circadian behaviour of diseases. This delivery systems release the drug rapidly and completely after a lag time, thus provide spatial and temporal delivery and increasing patient compliance, have generated increasing interest during recent years for a number of diseases and therapies [1]. The system is designed according to Circadian rhythm regulates many body functions in humans viz. metabolism, physiology, hormone production, behavior, sleep patterns, or biological clock which delivers the drug at the right time and at the right place and in the right amount thus, increasing patient compliance. In the pulsatile drug delivery system, initially there is no drug release after which there is an immediate or controlled release of the drug. In order to have a uniform therapeutic effect if a patient needs to have delayed absorption of drug, then targeting the drug to the colon would be useful. This type of conditions usually arises for diseases, which mainly persist during early morning hours like arthritis, asthma and angina etc [2, 3].

Pulsincap system comprises of a water insoluble capsule body, soluble cap and hydrogel plug. When this capsule comes in contact with the dissolution fluid, it dissolves and after a lag time, the plug gets pushed itself outside the capsule and rapidly releases the drug. The length of the plug and its point of insertion into the capsule controls the lag time [4].

The capsule bodies of size 0 were treated with formaldehyde vapors to make capsule body water insoluble. The amino group in the gelatin molecular chain could react with an aldehyde group of formaldehyde by a Schiff’s base condensation reaction to produce a water insoluble body. Caps were left untreated. When the capsule comes in contact with dissolution media, the cap gets solubilized and the hydrogel plug comes in contact with dissolution media and it gets hydrated and starts to swell and after ejection of the plug from the body, the drug release is facilitated.

Many drugs are used to control the blood pressure. Valsartan N-(I- oxopentyl)-N- [2-(14- tetrazol-5- yl)[ 1,1’– biphenyl]-4- yl] methyl]-L- valine [5]. Is an angiotensin II receptor blocker (ARB). It is popular for the treatment of hypertension as effective and well tolerated, a potent vasoconstrictor impacting after single and multiple dosing. It is available in doses of 40, 80 and 160 mg tablets or capsules, individually or in combination with diuretics. The administration time of Valsartan has a remarkable impact on its therapeutic efficacy. Pulsatile drug delivery system is effective in enhance benefits and reduce adverse effects of medications.Several studies have indicated that more than 80% of treated hypertensive patients are taking all their medication in the morning. Administration of angiotensin II receptor blockers (ARBs) at bedtime effectively controls blood pressure in essential hypertensive patients. Findings of the previous studies have also revealed that administering the antihypertensive drug at an appropriate timing is more important in treating patients with resistant hypertension than changing the drug combination to control blood pressure and revert to normal blood pressure pattern [6,7].

The rational of present investigation was to formulate and evaluate valsartan pulsatile pulsincap drug delivery system to treat hypertension according to Circardian rhythm of the body.

MATERIAL AND METHOD:

Materials:

Valsartan was obtained as gift sample from Lupin Pharmaceuticals (Pune) and HPMC K₄m, Ethyl Cellulose, Poly Vinyl Pyrolidone supplied by Research- Lab Fine Chem Industries (Mumbai). All the ingredients used in research work are analytical grade.

Drug Characterization:

UV Spectroscopy :

Calibration curve of valsartan was plotted with water, pH 1.2, 7.4 and 6.8 buffer with different concentration (1, 2, 3, 4, 5 μg/ml). The absorbance of the solution was taken at wavelength 250 nm against the blank solution on UV spectrophotometer.

(Drug Excipient Interaction Study) Fourier Transform Infrared (FT-IR) Spectroscopy:

Infrared spectroscopy was used to predict possible interaction between drug and excipient using a FTIR spectrometer (Jasco 4600) at 4000-650cm -1[8].

Preparation of Cross-Linked Gelatin Capsules:

Formalin treatment has been employed to modify the solubility of gelatin capsules. Exposure to formalin vapors results in an unpredictable decreases in solubility of gelatin owing to the cross-linkage of the amino group in the gelatin molecular chain aldehyde group of formaldehyde by Schiff’s base condensation.

Method:

Hard gelatine capsule of size 0 was taken. Bodies were separated from cap, 25 ml of 15% (v/v) formaldehyde was taken into desiccators and a pinch of potassium permanganate was added to it, to generate formalin vapours. The wire mesh containing the empty bodies of capsule was then exposed to formaldehyde vapours. The desiccators were tightly closed. The caps were not exposed leaving them water-soluble The reaction was carried out for 12 hrs after which the bodies were removed and dried at 50⁰C for 30 min to ensure completion of reaction between gelatine and formaldehyde vapours. The bodies were then dried at room temperature to removal of residual formaldehyde. These capsule bodies were capped with untreated caps and stored in a polythene bag [9,10].

Tests For Formaldehyde Treated Empty Capsules:

Various physical tests include visual defect, identification attributes as, dimensions, solubility studies of treated capsules, and chemical test were carried out simultaneously for formaldehyde treated and untreated capsules. The length and diameter of the capsules were measured before and after formaldehyde treatment, using dial calliper. Variations in dimensions between formaldehyde, treated and untreated capsules were studied.

Solubility Study of Treated Capsules:

For the Solubility study of treated capsules the capsule bodies were exposed to 15% formaldehyde solution in varying time intervals. Then formaldehyde exposed capsule bodies were dried in hot air oven. The solubility of bodies was tested in 0.1N HCL. The time at which the capsule dissolves or forms a soft fluffy mass was noted.

Qualitative Test For Free Formaldehyde:

Formaldehyde treated bodies about 25 capsules, cut into small pieces and taken into a beaker containing distilled water. This was stirred for 1 hrs with a magnetic stirrer, to solubilise the free formaldehyde. The solution was then filtered into a 50 ml volumetric flask, washed with distilled water and volume was made up to 50 ml with the washings.

Method:

1ml of sample solution, add 9 ml of water. One millilitre of resulting solution was taken into a test tube and mixed with 4ml of water and 5ml of acetone reagent. The test tube was heated in a water bath at 40^oC and allowed to stand for 40 min. The solution was less intensely colored than a reference solution prepared at the same time and in the same manner using 1ml of standard solution in place of the sample solution. The comparison was made by examining tubes down their vertical axis [11].

Preparation of Hydrogel Plug:

The pulsincap hydrogel plug was prepared by compressing equal amount of HPMC K4M and lactose using 7 mm punches and dies on rotary tablet press keeping variation in thickness and hardness values of tablet plug [12].

Characterization of Prepared Hydrogel Plug:

The prepared hydrogel plug evaluation was carried out for hardness, thickness and lag time test. hydrogel plugs were plugged to capsule bodies containing formulated granules and the cap was closed. The lag time test was conducted using7.4 pH for phosphate buffer for 6 hrs. USP II dissolution testing apparatus the drug release was observed [13].

Preparation of Valsartan Granules:

Valsartan granules were prepared by wet granulation method. The composition of different formulations used in the study is given in Table 1. The HPMC K100 and ethyl cellulose were sieved (no.60) separately and mixed with valsartan. The powders were blended and granulated with PVP K30. Isopropyl alcohol was used as granulating agents. The wet mass was passed through a mesh and granules were dried at 50⁰C.

Table 1: Composition of Valsratan

Ingredients	F 1	F2	F3	F4	F5
Valsartan	80	80	80	80	80
Hpmc K₄m	0	20	40	60	80
Ethyl Cellulose	80	60	40	20	0
Poly Vinyl Pyrolidine	10	10	10	10	10
Talc	2.5	2.5	2.5	2.5	2.5
Magnesium stearate	2.5	2.5	2.5	2.5	2.5

Characterization of Valsartan granules formulated with HPMC K4M:

The prepared granules were evaluated for different flow properties which include angle of repose, bulk density, tapped density, compressibility index, Hausner’s ratio, and drug content. The drug content was evaluated by an UV spectrophotometric method based on the measurement of absorbance at 250 nm.[13]

Formulation of pulsatile (modified pulsincap) drug delivery system:

Preparation of modified pulsincap :

Equivalent to 80 mg drug granules were filled in the capsule bodies and plugged with formulated hydrogel plug. The treated body and the cap of the capsules were sealed by using 5% ethyl cellulose ethanolic solution. The sealed capsules were coated with enteric coating (5% CAP) to reduce variability in gastric emptying time, coating was repeated until an expected weight gain of 8-12% was obtained [14].

Evaluation of modified Pulsincap:

Weight variation:

10 capsules were selected randomly from each batch and weight individually for weight variation.

Thickness of cellulose acetate phthalate coating:

The thickness of coating cellulose acetate phthalate to capsule was measured with screw gauge and expressed in mm [15].

In-vitro release profile:

Dissolution studies of valsartan pulsincap were carried out by using USP dissolution Type 1apparatus (Basket). In order to simulate the pH changes along the GI tract, three dissolution media with phosphate buffer pH 1.2, 7.4, 6.8 were sequentially used. When performing experiments, the pH 1.2 medium was first used for 2h (since the average gastric emptying time is 2hour), then removed and the fresh pH 7.4 phosphate buffer was added. After 3 hours fresh pH6.8 dissolution medium was added for subsequent hrs. in experiment 900 ml of the dissolution medium was used at each time. Rotation speed was 50rpm and temperature was maintained at 37ºC. 5ml of dissolution media was withdrawn at predetermined time intervals and fresh dissolution media was replaced. The withdrawn samples were analyzed at 250 nm, UV visible spectrophotometer [16].

RESULTS AND DISCUSSION:

Drug Characterization:

UV Spectroscopy:

From calibration curve of valsartan UV absorption maximum of drug was found at 250 nm. As per calibration curve correlation coefficient was found to be 0.999 (pH 1.2), 0.999 (pH 7.4),0.997 (pH 6.8). Calibration curve obeyed beer's law in the range of 1-5 μg/ml.

FT-IR spectroscopy:

The drug-excipients compatibility was assessed by IR spectra of drug, and drug-excipient by IR spectra .From the interpretation of spectra it is found that there is no worth change in the wave numbers of the drug and drug-excipients combination. Hence the drug and excipients are compatible with each other figure 1 and 2.

Evaluation of valsartan granules:

The evaluation result of prepared granules was show in Table 2. All formulation shows good angle of repose, flow property, hausner’s ratio and cars index.

Table 2: Evaluation of valsartan granules

Batch No.	Bulk density (g/cm³)	Tapped density (g/cm³)	Hausner’s ratio	Carr’s index (%)	Angle of repose
F 01	0.401	0.468	1.16	14.31	25⁰.18
F 02	0.341	0.402	1.17	15.17	21⁰.23
F 03	0.438	0.519	1.18	15.60	27⁰.81
F 04	0.398	0.465	1.16	14.40	26⁰.95
F 05	0.319	0.363	1.13	12.12	26⁰.21

Evaluation of hydrogel plug:

The formulated hydrogel plugs were evaluated by thickness, hardness and lag time. It was found that 90 mg plug showed 2 hrs lag time and 100 mg plug showed 3 hrs lag time. Therefore 100 mg plug was optimized.

Evaluation of formulation treated empty capsules:

The evaluation of treated empty capsule (cap and body) was carried out by length and diameter of capsules. The observations are recorded in Table 3.

Table 3: Evaluation of Treated Capsule

Initial Length of Capsule (mm)	Average Length after formaldehyde treatment (mm)	Initial Diameter of Capsule (mm)	Average Diameter after formaldehyde treatment (mm)
19.71	19.71±0.01	6.83	6.82 ± 0.009

Solubility study for the treated capsules:

When solubility studies was carried for capsule in 0.1 N HCL for 24 hrs, the observation was found that the normal capsules both cap and body dissolved within 15 minutes and another formaldehyde treated capsules, only the cap dissolved within 15 minutes remaining body of capsule intact for about 24 hours. Present work concludes that 8 hr formaldehyde treatment is sufficient to sustain the release for 18hr and found that the capsule has maintained the physical stability during the dissolution process.

Quantitative test for free formaldehyde:

The formaldehyde treated capsules were tested for the presence of free formaldehyde. The sample solution was not more intensely colored than the standard solution inferring that less than 20μg free formaldehyde is present in 25 capsule.

Weight variation and thickness of coating:

The capsules filled with granules pass the weight variation test as their weights are within the specified limits and the thickness of the cap coating was measured by using screw gauge which ranged from 0.055-0.072 mm.

In-vitro release studies:

In vitro dissolution test for capsules was performed in dissolution media of pH 1.2 and 6.8. The formulations F1, F2, F3, F5 showed more than 70% drug release Table 4. Batch F2 exhibited more than 90% drug release. During the dissolution studies, it was observed that, the enteric coat of the cellulose acetate phthalate was intact in pH 1.2, but dissolved in intestinal pH, leaving the soluble cap of capsule, which also got dissolved in pH 7.4 phosphate buffer. Thus, from % drug release studies of various formulation batches, F2 batch was selected as best formulation as it achieved maximum drug release in pH 7.4 phosphate buffer as compared to other formulation batches. The drug release from the formulation was observed to be decreased with an increase in the amount of polymer added in each formulation. Figure. 3

Table 4: Average % Drug release

Sr. No	Hrs	Average % Drug release
Sr. No	Hrs	F1	F2	F3	F4	F5
1	1	0	0	0	0	0
2	2	0	0	0	0	0
3	3	9.007±0.01	9.643±0.02	8.5±0.10	5.603±0.02	5.163±0.03
4	4	15.946±0.02	16.046±0.08	15.5±20.08	10.24±0.07	9.376±0.45
5	5	22.746±0.01	25.106±0.11	22.3±0.04	16.823±0.04	16.42±0.03
6	6	31.706±0.01	32.726±0.02	29.093±0.06	22.65±0.03	20.076±0.03
7	7	39.13±0.02	41.733±0.01	36.233±0.03	31.783±0.03	31.193±0.03
8	8	47.556±0.02	50.713±0.01	44.52±0.03	40.066±0.03	39.303±0.05
9	9	56.616±0.01	60.163±0.01	54.06±0.05	47.466±0.01	42.153±0.06
10	10	66.123±0.02	69.643±0.05	63.22±0.03	56.083±0.07	55.263±0.06
11	11	76.83±0.02	79.083±0.01	74.40±0.04	63.146±0.08	60.203±0.01
12	12	85.843±0.04	90.323±0.03	81.25±0.07	70.756±0.03	67.06±0.04

Fig 3: In Vitro Dissolution study

CONCLUSION:

Novel pulsincap formulations were successfully developed by filling of granules in a capsule body. The capsule body containing granules after plugging with a polymer, and sealed with a cap was completely enteric coated with 5% w/w cellulose acetate phthalate. Formulation F-2 was considered as the best formulations as they shown a complete lag time 24 of hours and released 90.36% at the end of 12 hours respectively. Thus, pulsincap formulations of can be suitable for optimum colonic delivery of valsartan in the treatment of hypertension as per chronotherapy.

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Received on 03.02.2018 Accepted on 19.04.2018

Asian J. Pharm. Tech. 2018; 8 (2):65-70 .

DOI: 10.5958/2231-5713.2018.00010.7