INTRODUCTION:

In developed countries like US the death rates, due to cardiovascular diseases decreased by 41% between 1990 and 2016. Whereas, in developing countries like India it was increased by around 34%¹. Use of tobacco, consumption of low amounts of fruit and vegetables, people with lower socioeconomic backgrounds are the prevailing causes for progression of cardiovascular diseases².

Individuals who are from lower economic backgrounds are not frequently receiving optimal therapy for cardiovascular diseases. In this regard it is required to design a dosage form which could available at low cost with slow and constant release of drug for a longer period of time there by reduces the frequent administration of drugs. Transdermal patches are the choice of dosage forms which have all these advantages so, the present study mainly focused to formulate a transdermal patch with antilipemic drug. Rosuvastatin Calcium is a statin which is a calcium salt form of rosuvastatin, with antilipidemic activity. Rosuvastatin inhibits hepatic hydroxymethyl-glutaryl coenzyme A (HMG-CoA) reductase by binding selectively and competitively. HMG-CoA reductase enzyme induces the conversion of HMG-CoA to mevalonate, a precursor of cholesterol, thereby reduces the risk of heart attack. Rosuvastatin currently available in the market as oral formulation i.e., tablets. Few reports on formulation of rosuvastatin as film coated, mucoadhesive bilayered buccal tablets, neosomes etc^3,4 but no reports are available on formulation of transdermal patch using Rosuvastatin calcium.

Delivery of drug through the skin to achieve a systemic effect of a drug is commonly known as transdermal drug delivery, and it differs from traditional topical drug delivery. The transdermal drug delivery system (TDDS) has been available commercially since early 1980s. TDDS provides a variety of significant clinical and therapeutic benefits over other drug delivery systems, such as oral and parenteral drug delivery systems. The low aqueous solubility of the drug initiated to apply the transdermal drug delivery to increase bioavailability and offers many more advantages over other conventional formulations⁵. It reduces the load on the liver and digestive tract by avoiding oral administration. It enhances patient compliance (painless and user friendly) and minimizes harmful side effects of a drug caused from temporary overdose⁶. It is convenient, especially notable in patches which require only once weekly application^7,8. From 1981 (First FDA approved transdermal patch) to current status number of drugs are formulated for TDD and employed for treating cardiovascular diseases, motion sickness, smoking cessation etc. TDDS are convenient for treating cardiovascular diseases in which the condition of the patients is not comfortable to take oral medication. The selected drug is having below 600 Daltons of molecular weight, below 200^oC of melting point, 20% of bioavailability and it is a potent drug⁹ to suit with the present transdermal patch formulation.

MATERIAL AND METHODS:

Materials:

Rosuvastatin-calcium was Gifted sample from Reine Life science, Hydroxy propyl methyl cellulose (Grade E50 LV premium), Polyvinyl propylene was purchased from Loba chemic Pvt. Ltd. Glycerol (Grade AR) was purchased from S.D fine chemicals, Dimethyl suphoxide (Grade AR) from Hi-pure fine chem., India. All chemicals and reagents used in the present study were of analytical reagent grade (AR Grade).

Methods:

I. Preformulation Studies:

Preformulation studies were carried out before formulating the drug substances to find out the possible interaction between drug and excepients. Compatibility study of drug with the excipients was determined by Fourier transform infrared (FTIR) spectroscopy (FT/IR Bruker) by taking mixture of excepients and drug in 1:1 ratio.

II. Formulation of transdermal patches:

i. General method of preparation of transdermal patches:

In the present study, transdermal patches of Rosuvastatin-calcium were prepared by solvent casting techniques using different ratios of polymers mentioned in Table 1. A circular Petri plates having diameter of 8.5 cm and height of 1 cm with a total surface area of 72.2cm² was fabricated for this purpose.

ii. Preparation of casting solutions:

The casting solutions were prepared by dissolving weighed quantities of polymers in DMSO as a solvent. The drug, plasticizer and permeation enhancers were then added to the various polymer solutions individually and thoroughly mixed to from a homogenous mixture. It was placed aside without any disturbances to allow the entrapped air to bubble out.

iii. Preparation of transdermal patches:

About 20 mL of casting solutions was poured into circular Petri plates, which was casted on propylene glycol. The Petri plates containing the casting solutions were allowed for drying at room temperature for 42 h and the patches were dried in an oven at 40-45^oC for 30 min in order to remove the residual solvents. These patches were wrapped in aluminium foil and stored in desiccator for further studies.

Table 1: Composition of transdermal patches

Ingredients	T₁	T₂	T₃	T₄	T₅	T₆	T₇
Rosuvastatin- Calcium in (mg)	10	10	10	10	10	10	10
Hydroxyl Propyl methyl cellulose in parts	4.5	4.0	3.5	3.0	2.5	2.0	1.0
Polyvinyl propylene in parts	0.5	1.0	1.5	2.0	2.5	3.0	4.0
Glycerol (mL)	30	30	30	30	30	30	30
DMSO (mL)	20	20	20	20	20	20	20

10%w/w of HPMC: PVP in DMSO:

III. Evaluation Parameters:

i. Thickness of the patch:

Using digital micrometer the thickness of the each patch loaded with drug was measured in different points and the average thickness and standard deviation was determined.

ii. Determination of average weight and weight variation:

As weight variation between the formulated patches can lead to difference in drug content and in-vitro behaviour, a study was carried out by weighing 7 patches in an electronic balance.

iii. Percentage moisture content:

The prepared patches were weighted individually and kept in a desiccators containing fused calcium chloride at room temperature for 24 h. After 24 h the patches were reweighted and the percentage moisture content was determined from the below formula.

Initial weight – Final weight

% Moisture content = –––––––––––––––––––––– X 100

Final weight

iv. Drug content:

UV spectroscopic method was used to determine drug content. Small patch with patch size of 5 cm²from different formulations (equivalent to 0.7mg of drug) was cut and dissolved in 100mL of pH 7.4 phosphate buffer. The patch was shaken thoroughly with buffer to release drug. After extraction of drug 1 mL of filtered solution was taken for determination of absorbance at 242nm.

v. Tensile strength:

Tensile strength of prepared patch was determined by using texture analyzer. Then film was cut into 10 × 10 mm strips and each strip was placed in tensile grips on the texture analyzer. Tensile strength was computed using load required to break the film. Tensile strength was the maximum stress applied to a point at which the film was broken¹⁰.

vi. Determination of percentage moisture uptake:

The weighed films kept in a desiccator at room temperature for 24 h was taken out and exposed to 75% relative humidity (a saturated solution of sodium chloride) in desiccators until a constant weight for the film was calculated as the difference between final and initial weight with respect to initial weight.

Final weight of patch - Initial weight of patch

% Moisture uptake = –––––––––––––––––––––––––––––––––– X 100

Final weight of patch

vi. In vitro drug release studies:

The paddle over disc method (USP apparatus 5) was employed for assessment of the release of the drug from the prepared patches. Dry films of known thickness were fixed over a glass plate with an adhesive. The glass plate is then placed in a 500 mL of the dissolution medium or phosphate buffer (pH 7.4), and the apparatus is equilibrated to 37 ± 0.5°C. The paddle was operated at a speed of 50 rpm by maintaining a distance of 2.5 cm with the glass plate. Samples (5 mL aliquots) can be withdrawn at appropriate time intervals up to 24 h and analysed by UV spectrophotometer. The experiment was performed in triplicate and the mean value was calculated.

vii. Skin irritation study:

Healthy rabbits (average weight 1.2 to 1.5 kg) were taken to perform skin irritation and sensitization tests. By shaving and cleaning with rectified spirit the dorsal surface of the rabbit was prepared for application of prepared patches. The patch was removed after 24 h and the skin was observed for the presence of any possible skin injury.

viii. Stability Studies:

Stability studies were conducted according to the ICH guidelines by storing the TTDS samples at 40±0.5°c and 75±5% RH for 6 months. The samples were withdrawn at 0,30,60,90 and 180 days and analyzed suitably for the drug content.

Figure 1: IR spectra of HPMC

Figure 2: IR spectra of PVP

Figure 3: IR Spectra of Drug

Figure 4: IR spectra of Drug, HPMC and PVP

RESULTS AND DISCUSSION:

In the present study, an attempt was made to prepare Rosuvastatin calcium loaded transdermal patch using polymers like HPMC and PVP employing glycerin as plasticizer, DMSO as the permeation enhancer and solvent to dissolve drug and polymers.

I. Pre-formulation studies:

i. FTIR Analysis:

Compatibility studies of the drug and the polymers were carried using BRUKER FTIR spectrometer and the spectra’s were given in the Figures 1 - 4. The spectra obtained from the mixture of polymers and drug was found to be matching with the spectra of the pure drug. There was no appearance or disappearance of any characteristic peaks, which confirmed the absence of chemical interaction between the drug and the polymer.

In the IR spectrum of Rosuvastatin-calcium the pure drug formed a number of peaks prominently in different wave numbers indicating the presence of functional groups and substituent.

The FTIR spectra of pure rosuvastatin calcium indicate the characteristic absorption stretch for strong NH stretch band (secondary Amines) at frequency at 3384.09cm^_1(3260-3600). Absorption Stretch for (O-H) absorption peak at (O-H) single bond alkane group and frequency at 2933.57cm^-1in range between (2850-3000). Absorption peak at (C = C) double bond region ketone group and frequency at 1510.1cm^-1 in the rage is (1620-1680) Rosuvastatin -calcium with HPMC. The absorption peak at 3472.24cm^-1 (O-H) alcohol group, 2929.94 (C-H) alkane group, 1057.88cm^-1(=C-O) ketone group, 846.89cm^-1(= C-H) alkene group. Rosuvastatin - calcium with PVP. The Absorption peak at 3398.45cm^-1(O-H) alcohol group, 2958.16cm^-1(C-H) alkane group, 1375.00cm^-1 (C-N) amine group, 1074.51cm^-1(C-O) alcohol group, 843.47cm^-1(=C-H) alkene group. The reports of FTIR studies indicate that there is no chemical interaction between the drug and excipients and they are compatible.

II. Physico-chemical parameters:

Seven patches of Rosuvastatin - calcium loaded with same amount of drug and different ratios of HPMC and PVP were prepared by solvent casting technique. The prepared patches were evaluated for physico - chemical parameters and in vitro drug release. The determined average weight of the patches with 15.2 cm² surface area and exhibited a significant change between the patches prepared with different polymer ratios. The average weight of the patches T_1-T₇ was given in the Table 2. Among the 7 patches, T₁-T₄has higher average weight compared to other patches and T₅-T₇ has less weight. This increase in weight of T₁-T₄ patches was due to usage of 10% w/w of polymers whereas in other formulation only 5% w/w polymers were used. There was no significant change in the thickness of the patches from T₁-T₇, which was determined by aerospace digital electronic micrometer and the results were shown in Table 2. This indicates that the patches were uniform and reproducible. The result of moisture content of the coded transdermal patches T₁-T₃ showed a significant change in the moisture content. Tensile strength was found to be higher for the patches T₁and T₂ when compared to other patches and hardness was found to be low for the patches T₁and T₂ when compared to other patches. All the patches showed uniform drug content, which was determined using Shimadzu UV-1700 spectrophotometer.

Table 2: Physico-chemical parameters of the formulated transdermal patches of Rosuvastatin - Calcium

Formulation Code	Polymer Ratio HPMC : PVP	Physical Appearance	Weight variation (grams)	Thickness (mm)	Tensile Strength (Kg/cm²)	Moisture Content (%)	Hardness (grams)	Moisture Uptake (%)	Drug Content (mg/cm²)
T1	4.5:0.5	Translucent, Flexible, Smooth	0.322± 0.006	0.127± 0.015	1.755	8.75± 0.015	12.76	10.12± 0.006	0.5634
T2	4:1	Translucent, Flexible, Smooth	0.322± 0.0006	0.20± 0.07	1.645	7.55± 0.007	16.59	9.88± 0.009	0.5456
T3	3.5 :1.5	Translucent, Flexible, Smooth	0.327± 0.0008	0.129± 0.001	1.599	7.09± 0.017	19.33	8.98± 0.013	0.5391
T4	3:2	Translucent Flexible, Smooth	0.304± 0.0005	0.122± 0.008	1.555	6.63± 0.002	20.33	8.17± 0.016	0.5128
T5	2.5:2.5	Translucent Flexible, Smooth	0.284± 0.005	0.124± 0.016	1.60	5.88± 0.01	21.20	7.76± 0.035	0.5542
T6	2:3	Translucent Flexible, Smooth	0.293± 0.0005	0.124± 0.005	1.504	5.14± 0.03	19.32	6.85± 0.048	0.6101
T7	1:4	Translucent Flexible, Smooth	0.286± 0.008	0.125± 0.006	1.551	4.36± 0.009	18.02	5.67± 0.009	0.6239

Table 3: Cumulative amount release of Rosuvastatin calcium transdermal patches (T₁ to T₇) formulated with polymers HPMC and PVP

Polymers ratio HPMC: PVP	1h	2h	3h	4h	5h	6h	8h	10h	12h	16h	20h
4.5 :0.5	0.0262	0.0349	0.0579	0.0685	0.0814	0.0902	0.1031	0.1380	0.1739	0.1739	0.4832
4:1	0.0211	0.0326	0.0464	0.0625	0.0786	0.0837	0.0984	0.1090	0.1491	0.1702	0.4556
3.5:1.5	0.0117	0.0331	0.0460	0.0520	0.0639	0.0736	0.0828	0.0902	0.1040	0.1187	0.4086
3:2	0.0138	0.0308	0.0414	0.0511	0.0598	0.0662	0.0745	0.0851	0.1003	0.1109	0.3835
2.5:2.5	0.0092	0.0142	0.0308	0.0404	0.0492	0.0612	0.0713	0.0768	0.0934	0.0952	0.356
2:3	0.0055	0.0110	0.0138	0.0340	0.0442	0.0547	0.0598	0.0823	0.0856	0.0943	0.348
1:4	0.0018	0.0027	0.0216	0.0312	0.0377	0.0478	0.0556	0.0648	0.0740	0.0860	0.3285

Table 4: Cumulative % release of Rosuvastatin calcium transdermal patches (T₁ to T₇) formulated with polymers HPMC and PVP

Time in h	HPMC:PVP 4.5:0.5	HPMC:PVP 4:1	HPMC:PVP 3.5:1.5	HPMC:PVP 3:2	HPMC:PVP 2.5:2.5	HPMC:PVP 2:3	HPMC:PVP 1:4
1	4.65	3.88	2.21	2.69	1.66	0.95	0.29
2	_6.2	5.98	6.14	6.01	2.57	1.81	0.44
3	10.29	8.51	8.53	8.07	5.56	2.26	3.46
4	12.17	11.47	9.64	9.96	7.3	5.58	5.01
5	14.45	14.42	11.8	11.66	8.88	7.24	6.04
6	18.01	16.35	15.65	14.92	11.64	8.97	7.67
8	28.29	28.05	25.36	24.54	29.87	19.8	18.92
10	44.5	49.99	46.73	36.6	33.86	28.5	24.4
12	58.26	67.32	59.29	41.56	46.85	38.03	39.87
16	69.87	71.21	62.02	61.62	57.19	45.46	43.79
20	85.77	83.56	75.8	74.78	64.27	57.02	52.66

Table 5: Physico – chemical evaluation of the developed transdermal patch (T₁) of Rosuvastatin-calcium during the stability studies at 40^oC

Time in days	Physical Appearance	Weight Variation (grams)	Thickness (mm)	Moisture content (%)	Moisture Uptake (%)	Drug content (mg/cm²)	Cumulative amount release (mg/cm) at 20 h	Cumulative percentage release at 20 h
0	Translucent, Flexiable, smooth	0.322± 0.006	0.157± 0.015	8.75±0.015	10.12± 0.006	0.5634	0.4832	85.77
15	No change	0.320± 0.015	0.0158± 0.015	8.81± 0.005	10.41± 0.014	0.5637	0.435	85.49
20	No change	0.330±0.008	0.161± 0.004	8.97± 0.03	10.73± 0.023	0.5628	0.4828	85.26
45	No change	0.383±0.018	0.165± 0.002	9.35± 0.027	11.24± 0.025	0.5619	0.4818	84.56

Table 6: Physico-chemical evaluation of the developed transdermal patch (T₄) of Rosuvastatin-calcium during the stability studies at 40^oC

Time in day	Physical Appearance	Weight Variation (grams)	Thickness (mm)	Moisture content (%)	Moisture Uptake (%)	Drug content (mg/cm²)	Cumulative amount release (mg/cm²⁾at 20h	Cumulative percentage release at 20h
0	Transparent, Flexible, Smooth	0.304±0.005	0.102±0.008	6.63±0.002	8.17±0.016	0.5128	0.3835	74.78
15	No change	0.310±0.010	0.106±0.006	6.10±0.001	8.20±0.012	0.5023	0.3827	75.23
20	No change	0.316±0.009	0.0107±0.005	6.70±0.004	8.32±0.014	0.5011	0.3789	74.54
45	No change	0.320±0.008	0.0108±0.004	6.90±0.18	9.15±0.016	0.4997	0.3725	74.12

Figure 6: Comparative cumulative percentage release of transdermal patch T₁ and T₄ during stability studies 40^oC

V. Stability studies:

The stability studies indicate that there was no change in physico-chemical and in vitro drug release of patches T₁and T₄patches shown in Table: 5, 6 and Figure 6.

IV. Skin irritation studies:

The skin irritation study reveals that the drug loaded and unloaded patches didn’t cause any noticeable signs of irritation or oedema on albino rat’s skin, indicating the skin compatibility of drug as well as polymer matrix.

V. Stability studies:

The stability studies indicate that there was no change in physico-chemical and in vitro drug release of patches T₁and T₄patches shown in Table: 5, 6 and Figure 6.

The patches showed a significant variation in their average weight, might be due to the variation in the proportions of polymers used. There was no significant change observed in the thickness of all the seven patches. Percentage moisture content and percentage moisture uptake was found to be high for the patches formulated with HPMC: PVP in the ratio (4.5:0.5) when compared to other patches formulated in different ratio of HPMC: PVP. The reason behind the screen might be the higher proportions of hydrophilic polymer; HPMC along with PVP in other ratios shows lesser moisture content and moisture uptake because of the highly hydrophobic polymer. For the patches with HPMC: PVP ratio (4.5:0.5) tensile strength was found to be high and hardness was found to be low when compared to other patches which might be due to the nature of the polymers. All the patches showed uniform drug content. The formulations T₁ showed a better in vitro drug release profile across the cellulose membrane, when compared to the other formulation. Chakshu et al., developed transdermal patch with PVP and HPMC in the ration of 3:1 exhibited in vitro % drug release of about 81.70%¹¹. Subramanian et al., formulated trandermal patch with atorvastatin nanosuspension using HPMC as polymer and reported the drug release of 86.4% ± 0.82% for 1.75 h¹². Matrix type transdermal drug delivery system of simvastatin was developed using natural and synthetic permeation enhancers¹³. The present study formulated trandermal patch with HPMC: PVP in the ration of 4.5:0.5 with released drug content of 85.77 of %. T1 formulation has good stability even after exposure to a temperature of 40^oC for a time period of 20 d with 85.77% of drug release. All the evaluated parameters and the % of drug release from the patches were within the limit. These patch formulations are especially convenient for geriatric purpose thus it avoids the inconvenience of oral formulation administration which are currently available in the market for Rosuvastatin – Calcium.

CONCLUSION:

Formulation T₁ was selected as best formulation among the seven formulations with more than 85% of cumulative drug release which was formulated with HPMC: PVP in the ration of 4.5:0.5 and the evaluation studies results were within the limit only. The formulation T₁ after exposure to 40^oC of temperature for 45 days exhibited good stability compared to T₄ formulation. The prepared patch is thin, flexible with good tensile strength and stability study of formulation T₁also confirms the suitability of method. This study further continued by formulation of keratinized patches with drug and the FTIR studies already shown that the drug and the keratinase enzyme were compatible with each other. This enzyme would help in better penetration of drug through the skin.

ACKNOWLEDGEMENTS:

We express our gratitude to Dr. L. Rathaiah, Chairman, Vignan Group of Institutions for providing necessary facilities to carry out the above research.

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Received on 23.12.2018 Modified on 30.08.2019

Research J. Pharm. and Tech. 2020; 13(10):4784-4790.

DOI: 10.5958/0974-360X.2020.00841.0