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Peer Review Article | Open Access | Published 3rd April 2024


Improved Dissolution and Solubility Characteristics of Clopidogrel Bisulphate using Gelucire 44/14

Urvashi Sharma¹, Shikha Agrawa ², Mahavir Chhajed³, Sumeet Dwivedi⁴ | EJPPS | 291 (2024) | https://doi.org/10.37521/ejpps.29103 | Click to download pdf  


 

Abstract 

Clopidogrel bisulphate is a poorly aqueous soluble drug belonging to BCS Class II. The drug is widely used to treat blood clotting in patients with peripheral, coronary, and cerebrovascular disorders, but its low bioavailability raises concern. The present study involves an effort for enhancing the solubility and drug release by transforming the drug into solid dispersions. The solid dispersions of clopidogrel bisulphate were prepared with Gelucire 44/14 using solvent evaporation method. The prepared physical mixture and solid dispersions were characterized for drug-carrier interaction, drug content, solubility, and dissolution rate. Results confirmed the increase in drug solubility with increasing polymer concentration. The dissolution profile was found to substantially improve from solid dispersion with maximum drug release in the ratio of 1:5 on comparing it with pure drug and physical mixture. FT‐IR spectra of selected solid dispersion revealed no chemical interaction between drug and polymers while the presence of the drug in the amorphous state was confirmed by DSC thermograms and X-ray diffraction, indicating better dissolution characteristics. The solid dispersions were also found to be stable under accelerated stability conditions.

   

Keywords: Clopidogrel bisulphate, Bioavailability, Solid dispersions, Gelucire 44/14, Solubility Enhancement


1.Introduction 

 

With improvement in combinatorial chemistry and high throughput screening, modern drug discovery strategies continue to flood drug development pipelines with a large number of poorly soluble New Chemical Entities (NCEs). A lot of scientists are involved in the invention of NCEs, but the success rate is low as almost 40% to 70% of NCEs are poorly water soluble. In general, a drug with poor water solubility will have restricted absorption due to slower rate of dissolution, while a drug with poor membrane permeability will have limited absorption due to penetration rate. Hence, for poorly water-soluble drugs raising the solubility along with rate of dissolution and increasing the permeability of poorly permeable drugs are thus two fields of pharmaceutical research that concentrate on enhancing the oral bioavailability of active substances.¹⁻²

Solubility, being one of the most important physicochemical elements that affects a drug's absorption and thereby its therapeutic action, is a crucial consideration. If a drug’s aqueous solubility is poor, both designing dosage form and achieving effective therapeutic action may be difficult. Poor drug aqueous solubility and dissolution rate have a huge impact on its oral bioavailability.²

Numerous commercially feasible approaches, including liquisolid, nanomorph, in-situ micronization, and co-precipitation utilizing antisolvent, are available to increase the solubility and rate of dissolution of poorly soluble medicines. Solid dispersion is the method that formulators find to be most promising due to its simplicity in preparation, optimization, and reproducibility.³

Solid dispersion is a combination of drug which is hydrophobic with hydrophilic matrix. The technique involves dispersing the active moiety in an inert carrier molecule or polymer. The carrier dissolves when the solid dispersion is exposed to media, and the drug releases as tiny colloidal particles. The increased surface area provides faster dissolution with improved drug bioavailability.⁴

This enhanced solubility is also due to achievement of the amorphous state, which is thought to be more soluble than the crystalline state and is one of the fundamental concepts behind the formulation of solid dispersion. This can be described by the fact that in the amorphous state no structure is there which needs energy to disrupt the crystal lattice as in that of crystalline substances.⁵

Several hydrophilic carriers have been researched for improving the dissolution properties and bioavailability of poorly aqueous soluble drugs, including gelucires, eudragits, HPMC, PEG etc.⁶

One such attempt has been done in this research for improving the solubility of BCS Class II drug Clopidogrel Bisulphate.

Clopidogrel bisulphate, a white to off-white powder, is a specific inhibitor of adenosine diphosphate (ADP) binding to its platelet receptor and consequently prevents the aggregation of platelets. Due to its poor aqueous solubility, it has very low oral bioavailability. So, the aim of the present work is to formulate the solid dispersions of clopidogrel bisulphate using Gelucire 44/14 for enhancing solubility and thereby the dissolution profile of drug.⁷



Figure 1: Structure of Clopidogrel Bisulphate

Solid dispersions are one of the easiest and conventional technologies that has been updated with the advancement of novel carriers. The third-generation solid dispersions including nonionic surfactants such as Gelucire can be used alone or in combination to enhance the dissolution and oral bioavailability of poorly soluble drugs which can be easily formulated thereafter as sustained or immediate release tablets or nanoformulations. The prepared solid dispersions showed optimum increase in solubility and drug dissolution rate when compared with previous studies, proving the Gelucire being a viable alternative to other carriers. Although in-vivo pharmacokinetic profiling is needed to confirm the bioavailability enhancement of solid dispersions.



 

Materials and Methods

 

Clopidogrel bisulfate was a gift sample from IPCA laboratories, Indore, India. Gelucire 44/14

was obtained from Aurobindo Pharma Ltd. All other ingredients were of analytical grade.


Methods

Determination of λ max

There are various techniques of 3D printing. The different techniques have shown a variety of advantages to various types of formulations. These different techniques are favourable to a range of drugs which in total can produce the formulation of any sensitive drug. Sensitivity could be towards heat, shape, etc. 3D printed formulations have shown better effects than conventional drug dosage forms[27]. As a result, this approach has given improved dissolution and release patterns. Some of the 3D printing techniques are considered below.      100 mg of pure clopidogrel bisulphate was accurately weighed and transferred to a 100 ml volumetric flask and volume was made up to 100 ml with methanol to give a solution of 1000μg/ml. A 10 ml sample of this solution was pipetted into a 100 ml volumetric flask, and the volume was made up with methanol to produce a solution with a concentration of 100μg/ml. A dilution of 20 µg/ml concentration was made from the above stock solution and the resulting solution was scanned between 200 nm and 400 nm.⁸,⁹


Preparation of Calibration Curve

100µg/ml stock solution was obtained by taking 10 mg of clopidogrel bisulphate and dissolving with 100 ml of methanol The stock solution was appropriately diluted to achieve different concentration ranging from of 10, 20, 30, 40, and 50 μg/ml and absorbance was noted at 220nm.¹⁰


Phase Solubility Studies

The Higuchi and Connors method was used to determine solubility. An excess quantity of the drug was introduced to a 10 ml volumetric flask having different concentrations of aqueous solution of carriers i.e. 5%, 10%, 15%, 20%, 25% and 30%. The samples were allowed to equilibrate by shaking for 24 h at 37 ± 1°C and the resulting solutions were subjected to filtration followed by analysis at 220 nm after appropriate dilution.¹¹


Preparation of Physical Mixture by Trituration Method 

Clopidogrel bisulphate with carrier in different ratios of 1:1, 1:3, 1:5 (FP1, FP2, FP3) were taken and triturated lightly for 5 min in a mortar until a homogenous mixture was obtained. This was passed through sieve no.80 to obtain uniform physical mixtures (PMs) and stored in desiccators for further use.¹²


Preparation of Solid Dispersions by Solvent Evaporation Method

The drug and the polymer were weighed in different ratios 1:1, 1:3, 1:5 (FS1, FS2, FS3). Accurately weighed quantities of polymer were carefully transferred into a beaker and dissolved in an adequate quantity of methanol. To these solutions, accurately weighed quantities of drug were added and allowed to dissolve. The solvent was then rapidly evaporated by stirring on a magnetic stirrer with the aid of mild heat of about 40 °C for 1hr. The obtained residue was dried for 2 hrs. and stored in desiccators overnight. Next day the dried residue was ground in a mortar and sieved through mesh # 80.¹³⁻¹⁴


Table 1: Composition of Optimized Formulation of Clopidogrel Bisulphate Solid Dispersion and Physical Mixture¹³⁻¹⁴



Characterization of Solid Dispersions
Characterization of Solid Dispersions

Aqueous Solubility Study

For the solubility study, excess formulations (drug, physical mixtures and solid dispersions) were added in a stoppered conical flask with 10 ml of distilled water and shaken for 8 hours at 60 rpm (37±1oC) on an orbital shaker. Solutions were kept for 24 h after shaking to achieve equilibrium. From this, 2 ml

aliquots were taken out and filtered through 0.45µm Whatman filter paper. After appropriate dilution with distilled water, the filtrate was analysed spectrophotometrically at 220nm against a blank and readings were recorded in table 2.¹⁵

 

Drug Content 

The drug content was determined by dissolving clopidogrel bisulphate in an amount equivalent to 10mg of solid dispersions and physical mixture with 10ml of methanol, followed by stirring on a magnetic stirrer for 10 min. The solution was filtered through a membrane filter (0.45 µm), diluted suitably and drug content was assessed at 220nm using a UV spectrophotometer.¹⁶


Dissolution Rate Studies

An in-vitro drug release study was performed using USP type II apparatus (Paddle method) at a speed of 50 rpm. Accurately weighed quantities of pure drug, physical mixture and solid dispersion containing 75 mg equivalent of clopidogrel bisulphate were added to a dissolution medium consisting of 6.8 phosphate buffer maintained at 37±0.5oC. The dissolution was carried out for 1 h and samples of 5ml were withdrawn at adequate intervals. An equal volume of fresh dissolution medium was replaced to keep the total volume constant. The filtered samples were analyzed spectrophotometrically at 220 nm using a UV‐visible spectrophotometer.¹⁷


FTIR Studies

The FTIR spectra of the drug, Gelucire 44/14 polymer and solid dispersion in 1:5 ratio was recorded using a FTIR spectrophotomer. Dried powdered potassium bromide was thoroughly combined with the powdered sample and then compressed into a disc using a hydraulic pellet press. The prepared disc was kept in a sample holder inside an IR spectrophotometer and the spectrum was recorded after scanning between 4000-400 cm⁻¹.¹⁸


Differential Scanning Calorimetry (DSC)

Differential Scanning Calorimetry (DSC) studies were carried out using DSC (Model DT-60, Shimadzu, Japan). Samples equivalent to 2-5mg of the drug were heated in hermetically sealed aluminum pans and heated over a temperature range of 0-300°C at a constant rate of 10˚C/min under a stream of nitrogen.¹⁹


Powder X-ray diffraction (XRD)

X-ray powder diffraction patterns for the samples were examined using powder X-ray powder diffractometer (Shimadzu, Japan) which uses a copper target that operates at a voltage of 40 Kv and a current of 30 mA. With a step size of 0.01º, the scanning was performed over 2θ/s range of 5º to 60º.²⁰


Stability Studies

The selected solid dispersions of clopidogrel bisulphate with Gelucire 44/14 (FS3) were subjected to an accelerated stability study. The solid dispersions of about 1 gm were filled in an amber colored screw

capped bottle and stored at temperature conditions such as room temperature (25oC) and 40±2oC/75±5% RH using a desiccator containing calcium chloride, for a period of 3 months. Samples were withdrawn at adequate intervals and visually examined for any physical change. The percent drug content and in-vitro dissolution rate were also estimated.²¹


 

Results and Discussion

Phase Solubility Studies

The result of phase solubility of clopidogrel bisulphate in Gelucire 44/14 polymer indicated that the solubility increases with increasing concentration of the carrier, as shown in Table 2 (Figure 4). The plot between clopidogrel bisulphate and Gelucire 44/14aqueous solution in 30% w/v showed the highest phase solubilization as compared to other polymeric solutions.


Figure 2: UV Spectra of Clopidogrel Bisulphate at 220nm


Figure 3: Calibration Curve of Clopidogrel Bisulphate at 220nm


Table 2: Solubility of Clopidogrel Bisulphate in Gelucire 44/14


Figure 4: Phase Solubility Curve of Clopidogrel Bisulphate in Gelucire 44/14



Aqueous Solubility Study

From the solubility data, it was found that solid dispersions prepared using Gelucire 44/14 in the proportion of 1:5 have good solubility as compared to solid dispersions with other drug polymer ratios, physical mixtures, and pure drug. Results in Table 4 confirmed that clopidogrel bisulphate and Gelucire 44/14in 1:5 has shown enhancement in drug solubility by 20-fold.


Drug Content

The drug content for solid dispersions ranged between 94.72±0.35% and 99.55±0.50% with 88.69±0.16 to 96.31±0.28 for physical mixtures. The results obtained for drug content (Table 3) indicated

homogenous distribution of the drug in the prepared physical mixtures and solid dispersion formulations.


Table 3: Saturation Solubility of Clopidogrel Bisulphate-Gelucire Solid Dispersions and Physical Mixture



Dissolution Rate Studies

In-vitro dissolution of solid dispersion batches (FS1-FS3), physical mixtures (FP1-FP3) and pure drug are tabulated in Table 4 and shown in Figure 5. All the formulations exhibited an increased dissolution rate in comparison to pure clopidogrel bisulphate. Solid dispersions of drug clopidogrel bisulphate with Gelucire 44/1 in the ration of 1:5 showed a higher dissolution rate of 93.17±0.10 and were selected for further studies.


Table 4: Cumulative % Drug Release of Solid Dispersions and Physical Mixtures




Figure 5: Effect of Drug: Polymer ratios on Dissolution of Clopidogrel Bisulphate


FTIR

The FTIR spectra of the drug and polymer solid dispersion in 1:5 ratios were recorded with a FTIR spectrophotometer. From the FTIR spectra of clopidogrel bisulphate, Gelucire 44/1 and solid dispersion, it was found that no functional group changed when clopidogrel bisulphate reacted with Gelucire 44/14. So, they were found to be compatible in solid dispersions.



Figure 6: IR Spectra of Clopidogrel Bisulphate, Gelucire 44/14 and Solid Dispersion


DSC

DSC studies were performed to identify the interaction if any between clopidogrel bisulphate and Gelucire 44/14 on the individual components. From the graph (Figure 7), it was concluded that the DSC curve of clopidogrel bisulphate showed one endothermic peak at nearly 183˚C with a broad endothermic peak of Gelucire 44/ 14 at around 43˚C. Thermograms of solid dispersions showed the absence of a clopidogrel bisulphate peak, suggesting either the loss of the drug’s crystalline nature or complete solubility of clopidogrel in liquid phase of the polymer.




XRD

The clopidogrel bisulphate solid dispersions were studied for XRD to determine whether the solid dispersions are crystalline or amorphous. The X-ray pattern of pure clopidogrel bisulphate revealed intense and sharp peaks, indicating its crystalline nature as demonstrated by sharp peaks observed at, 2θ values of 13.03º, 15.62º, 17.08º, 17.69º, 18.48º, 20.9º, 25.16º, 25.69º as shown in Figure 8. But the solid dispersion did not show the corresponding peak, which was present in clopidogrel bisulphate. So, enhancement of the dissolution of the drug was attributed to decreased crystallinity of the drug.



Figure 8: Powder X-ray Diffraction a) Clopidogrel Bisulphate b) Gelucire 44/14

c) Solid Dispersion (1:5)




Stability Studies

Stability studies of FS3 formulation were performed for drug content and in vitro drug release studies for 3 months at accelerated stability conditions as per ICH guidelines. From the results, it was concluded that the optimized formulation was stable for a three-month period and retained most of its properties with minor differences. The results are summarized in table 5.


Table 5: Drug Content and Cumulative % Drug Release of Optimized Solid Dispersion (FS3) for Stability Study



Conclusion

The current study highlighted the easiest method to enhance the aqueous solubility by preparing solid dispersions. In our study, the solid dispersion of clopidogrel bisulphate with Gelucire 44/14 were prepared using the solvent evaporation method and they significantly improved the drug solubility and in vitro drug release in all proportions when compared with pure drug and physical mixtures.

However, the concentration dependent enhancement in solubility was observed on increasing the drug polymer ratio. The solid dispersion with highest proportion of Gelucire 44/14 i.e.1:5 showed the maximum solubility with dissolution and hence was chosen for further studies. Results of FTIR, XRD and DSC confirmed the presence of drug in the amorphous state within solid dispersions. The optimized formulation also exhibited no significant changes over the duration of three months stability testing, indicating sufficient stability. Overall, the solid dispersion remains to be a promising and simplest technique for enhancing the solubility of drugs.



 

References

1. Sharma KS, Sahoo J, Agrawal S, et al. Solid dispersions: A technology for improving bioavailability. J Anal Pharm Res. 2019;8(4):127-133.

2. Aggarwal S, Gupta GD, Chaudhary S. Solid dispersion as an eminent strategic approach in solubility enhancement of poorly soluble drugs. Int J Pharm Sci Res. 2010;1(8):1–13.

3. Patel AK, Budholiya P, Tyagi CK. Formulation, development and evaluation of solid dispersions for enhancement of solubility and dissolution rate of clopidogrel bisulfate. Asian Journal of Pharmaceutical Education and Research. 2020; 9(4): 76-86.

4. Sarkar R, Hossain ASM, Islam S, Faroque ABM. Effect of hydrophilic swellable polymers on dissolution rate of Atorvastatin using simple physical mixing technique. Indian J of Novel Drug delivery. Apr-Jun 2012; 4(2):130-138.

5. Sridhar I, Doshi A, Joshi B, Wankhede V, Doshi J. Solid Dispersions: An Approach to Enhance Solubility of poorly Water-Soluble Drug. Journal of Scientific and Innovative Research. 2013; 2 (3): 685-694.

6. Sinha S, Ali M, Baboota S, Ahuja A, Kumar A, & Ali J. Solid dispersion as an approach for bioavailability enhancement of poorly water-soluble drug ritonavir. AAPS Pharm. Sci. Tech. 2010; 11(2), 518–527.

7. Patel V, Kukadiya H, Mashru R, Surti S, Mandal S. Development of Microemulsion for Solubility Enhancement of Clopidogrel. Iranian Journal of Pharmaceutical Research. 2010; 9(4): 327-334.

8. The United States Pharmacopeial Convention USP 39 Official Monographs / Clopidogrel 3247, Official from May 1, 2016 Copyright (c) 2015.

9. Nagavi JB, Gurupadayya B. Development and Validation of Bio-Analytical RP-Ultra Fast Liquid Chromatographic Method for Simultaneous Estimation of Clopidogrel and Rosuvastatin in Human Plasma. Int J Pharm Sci Res. 2015; 6(1): 219-25.

10. Gurav S, Venkatamahesh R. Development and validation of derivative UV-Spectropotometric methods for quantitative estimation of clopidogrel in bulk and pharmaceutical dosage form. Int.J. ChemTech Res., 2012; 4(2): 497-501.

11. Higuchi T, Connors KA. Phase-solubility techniques. Adv Anal Chem Instrum. 1965;4:117–212.

12. Sharma A., Jain CP., Tanwar YS. Preparation and Characterization of Solid Dispersions of Carvedilol with Poloxamer 188. Journal of the Chilean Chemical Society. 2013; 58(1), 1553-1557.

13. Sharma A, Jain CP. Preparation and characterization of solid dispersions of carvedilol with PVP K30 A. Research in Pharmaceutical Sciences. 2010; 5(1): 49-56.

14. Dangre PV, Godbole MD, Ingale PV, Mahapatra DK. Improved Dissolution and Bioavailability of Eprosartan Mesylate Formulated as Solid Dispersions using Conventional Methods. Indian Journal

of Pharmaceutical Education and Research. 2016; 50(3), S209-S217.

15. Sharma U, Joshi A, Vyas N, Malviya S, Kharia A. Solubility enhancement of clopidogrel bisulfate by solid dispersion technique using carboxymethylcellulose sodium and xanthan gum. Journal of Drug Delivery and Therapeutics. 2017; 7(7):35-37.

16. Murugesan M, Sankaranarayanan V. Development and characterization of solid dispersion-based orodispersible tablets of cilnidipine. Beni-Suef Univ J Basic Appl Sci. 2022; 11:83.

17. Tomar V, Garud N, Kannojia P, Garud A, Jain NK, Singh N. Enhancement of solubility of acyclovir by solid dispersion and inclusion complexation methods. Der Pharmacia Lett, 2010; 2: 341-52.

18. Muralichand G, Bhikshapathi DVRN. Preparation and in vitro Evaluation of Solid Dispersions Containing Nifedipine. Int. J. Pharm. Sci. Drug Res. 2018; 10(4): 260-267.

19. Singh SK, Som S, Shankhwar U. Formulation and optimization of solid dispersion of Clopidogrel with PEG 6000. Journal of Appl Pharm Sci., 2011; 1(08): 217-226.

20. Medarević D, Cvijić S, Dobričić V, Mitrić M, Djuriš J, Ibrić S. Assessing the potential of solid dispersions to improve dissolution rate and bioavailability of valsartan: In vitro-in silico approach. Eur J Pharm Sci. 2018;124:188-198.

21. Wagh SR, Arsul VA, Gadade DD, Rathi PB. Solubility Enhancement of Antiviral Drug-Acyclovir by Solid Dispersion Technique. Indo Am. J. Pharm. Sci, 2015;2(10).


 

Authors

Urvashi Sharma¹, Shikha Agrawa ², Mahavir Chhajed³, Sumeet Dwivedi⁴


1. Faculty of Pharmacy, Medi-Caps University, Indore, 452001, Madhya Pradesh, India

2. Shivajirao Kadam Institute of Pharmaceutical Education and Research, 452001, Madhya Pradesh, India

3. Vidyasagar College of Pharmacy, Indore, 452010, Madhya Pradesh, India

4. Acropolis Institute of Pharmaceutical Education and Research, Indore, 453771, Madhya Pradesh, India


* Corresponding author:

Sumeet Dwivedi⁴




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