INTRODUCTION:

Solubility is one of the most common challenges in drugs formulation, especially for the oral form. In fact, about 40% of newly developed drugs candidate are associated to poor water solubility or biological fluids¹, which can limit their effectiveness by a low bioavailability and absorption². Moreover, the low solubility of drugs makes the formulation in both stable and effective form challenging³.

Various approach can be employed to overcome solubility challenges as reducing particle size⁴, salt formation⁵, the use of solubilization agent as co solvent⁶, surfactant and co surfactant or cyclodextrins (CD)⁷.

These choices must be rigorously made during drug´s pharmaceutical development stages and justified, which may require additional testing and documentation. According to the Biopharmaceutical Classification System (BCS), Class II « low solubility, low permeability » and Class IV « low solubility, high permeability »drugs are those with the most solubility problems⁸.

Among the solubilization methods, the use of Cyclodextrin (CD) can be considered in a formulation with the Active Pharmaceutical Ingredient (API) alone, or in combination with other solubilizers⁹. CD are widely used in pharmaceutical industry to improve not only drugs solubility, but also stability by protecting the API from environmental degradations¹⁰. It is cyclic oligosaccharides linked together by alpha-1,4 glycosidic bonds, and composed of six, seven, or eight glucose units¹¹. Their cone-shaped structure with a hydrophilic outer surface, and a hydrophobic cavity in the center allows insoluble drug´s encapsulation then solubilization¹². The other advantage of CD uses is reducing the amount of drug needing for intended therapeutic effect¹³. Furthermore, CDcan act as drug delivery vehicles, as they can target specific tissues or cells and release drugs in a controlled manner¹⁴.

Polyvinylpyrrolidone (PVP) is a water-soluble polymer made from the monomer N-vinylpyrrolidone¹⁵, it is commonly used as a binder, coating agent, and disintegrant in oral dosage forms¹⁶. PVP is also used as a solubilizer, stabilizer, and viscosity enhancer in liquid formulations¹⁵. Furthermore, high molecular polymers are suitable to increase solubility¹⁷, as it is the case of Poly Ethylene Glycol 6000¹⁸.

The CD in combination with PVP alone or in the presence of one, two or three of hydrophilic polymer could be interesting to investigate in aim to evaluate their effect on solubilizing BCS Class II and IV drugs and dissolution rate¹⁹.

Valsartan (VST), Furosemide (FSD), and Celecoxib (CCX) are three different drugs that are known to have solubility issues, which can impact their effectiveness and absorption in the body. VST is an angiotensin II receptor blocker, commonly used to treat hypertension and heart failure²⁰, FSD is a loop diuretic used to treat conditions like edema and hypertension²¹, and Celecoxib is a nonsteroidal anti-inflammatory drug often prescribed for pain relief and inflammatory issues²². VST, FSD and CCX are known for their poor water solubility, which can limit their dissolution and absorption in the gastrointestinal tract, andare classified as class II for VST and CCX, and class IV for FSD.

The aim of this work is to study the effect of the use of cyclodextrin combined with each PVP, and PEG 6000 individually, then combined, and the enhancement of solubility and dissolution rate on three BCS class II Celecoxib and Valsartan, and Class IV Furosemide in a serie of 2³factorial study.

MATERIAL AND METHODS:

Material:

API were all gift samples, CCX from Pharmaceutical Institute Industry, Furosemide from Pharma 5, and Valsartan from Sheikh Zaid Foundation Bioequivalence Center.

Cyclodextrin-beta was bought from Sigma Laboratory, PVP and PEG were purchased from BASF (Ludwigshafen, Germany) and Merck (Germany), respectively. Ethanol was purchased from VWR BDH Prolabo® (France).

All other materials were distilled water and reagents.

Analytical method:

Absorbance measurements were carried our using UV/Visible spectrophotometer (Shimadzu UV 2450, Japan). Linearity, precision, interference and accuracy were validated for the methods that obeyed Beer Lamber´s law in the concentration range studied. A Standard drug solution was assayedseven times (n=7), coefficient variation and relative error were less than 1% and 0,5%.

Solubility studies:

An excess of each API (50mg) was added to 10mL of each fluid studied and was placed in conical capped flaks. The mixtures were stirred for 24 hours at room temperature (25±1°C) on a magnetic stirrer. After 24 hours of stirring, 2ml supernatants were collected and filtered immediately through Whatman paper (0.45µm). The samples were then diluted in 1:10 ratio (0,1mL of sample to 1mL ethanol) and essayed at 249nm for VST, 256nm for FSD and 215nm for CCX, replicated 5 times for each (n =5).

Dissolution Studies:

To assess individual and combined effect of each excipient, ß-CD, PVP, PEG 6000, on dissolution rates of VST (i), FSD (ii) and CCX (iii), solid drug- ß-CD inclusion complexes were prepared with and without PVP, and PEG 6000 per 2³factorial designs²³.

Kneading method was used to prepare CD-API solid inclusion complexes²⁵, in ration 2:1 with and without PEG 6000 (2%) and PVP (2%) as described in other API solubility studies. For this purpose, respectivelyVST, CCX and FSD were triturated in a mortar with a small volume of a blend of water methanol blend in 1 :1. The resulting thick paste was kneaded for 30 minutes, then dried at 55°C until dry. The dried mass was ground to powder with a mortar and sieved to No. 120 mesh.Drug and CD-API complexes equivalent to 40mg of VST, 60 mg of FSD and 100 mg of CCX was used in each test.

Two levels of ß- CD-API (0 and 2:1 ratios of drug: ß-CD) and two levels of each PVP and PEG 6000 (0 and 2% for each) were picked, so we had eight sample´s types involved in the 2³factorial study, and for each mixture, 5 hard capsules of size 0 were filled with the studied complex: Pure drug (1); ß-CD-API(2:1) inclusion binary complex (a); API–PEG 6000 (2%) binary mixture (b); ß-CD-API (2:1)– PEG 6000 (2%) ternary complex (ab); API – PVP (2%) binary mixture (c); ß- CD-API (2:1)– PVP (2%) ternary complex (ac); API–PEG 6000 (2%) – PVP (2%) ternary complex (bc); and ß- CD-API (2:1)– PEG 6000 (2%) – PVP (2%) complex (abc).

Dissolution rate were determined using dissolution test apparatus II (Pharma test)with a basket stirrer at 50rpm. API and prepared ß-CD-APIcomplex containing 40mg of VST, 60mg of FSD, and 100mg of CCX in each sample were considered and the dissolution rates were evaluated respectively in 900ml of Phosphate buffer pH 6.8, alkaline borate buffer of pH 8.4 and Phosphate buffer of pH 7.4 respectively, under 37±1°C temperature. Regularly, equivalent of 10ml of dissolution media samples were filtered through Whatman paper, diluted in 1:10 ethanol ratio, then essayed at 249, 256, and 215 nm respectively for VST, FSD and CCX, the equivalent was replaced then by fresh fluid. Dissolution experiment were replicated four times each (n=5).

Anova data analysis:

Anova variance analysis of factorial experiments was made to analyze solubility and dissolution results, to highlight individual and combined effects of involved factors namely ßCD, PVP and PEG 6000.

RESULTS AND DISCUSSION:

Two levels of ßCD (0 and 5 mM) (Factor a), two levels of PEG 6000 (0 and 2%) (Factor b), and two levels of PVP (0 and 2%) (Factor c), were adopted in each experiment to evaluate individual and combined effects of each excipient on aqueous solubility of VST (i), FSD (ii), and CCX (iii) in a serie of 2³factorial experiments. The corresponding treatments were purified water (1), water containing 5mM of ßCD (a); water containing 2% PEG 6000 (b); water containing 5mM ßCD and 2% PEG 6000 (ab); water containing 2% PVP (c); water containing 5mM ßCD and 2% PVP (ac); water containing 2% PEG 6000 and 2% PVP (bc) and water containing 5mM ßCD and 2% of each of PEG 6000 and PVP (abc).

Tables 1, 2 and 3 shows each API´s solubility in each mentioned fluid that was evaluated (n=5).Aqueous solubilities of the studied API were enhanced by ßCD, PEG 6000 and PVP alone and in combination.

An ANOVA analysis was made to solubility data to determinate the significance of main and combined effects of effects of ß-CD, PEG 6000 and PVP on solubility. Individual and combined effects of ß-CD, PEG 6000 and PVP on VST (i), FSD(ii), and CCX(iii) were highly significant (P < 0.01).

Solubility Results:

Table 1: Solubility of CCX in Various Fluids as per 2³Factorial Study

Celecoxib
Fluids	Solubility (mg/ml) (n=5) (x±sd)	Increase in Solubility (Number of Ratios)	Significance
Distilled water (1)	0.152±0.04	-	-
Water containing 5 mM ßCD (a)	0.204±0.02	1.34	P < 0.01
Water containing 2% PEG6000 (b)	0.341±0.07	2.24	P < 0.01
Water containing 5 mM ßCD and 2% PEG6000 (ab)	0.753±0.03	4.95	P < 0.01
Water containing 2% PVP ( c)	0.278±0.06	1.83	P < 0.01
Water containing 5 mM ßCD and 2% PVP (ac)	0.382 ±0.05	2.51	P < 0.01
Water containing 2% PEG6000 and 2% PVP (bc)	0.387±0.02	2.55	P < 0.01
Water containing 5 mM ßCD, 2% PEG6000 and 2% PVP (abc)	0.592±0.01	3.89	P < 0.01

Table 2: Solubility of FSD in Various Fluids as per 2³Factorial Study

Furosemide
Fluids	Solubility (mg/ml) (n=5) (x±sd)	Increase in Solubility (Number of Ratios)	Significance
Distilled water (1)	0.023±0.01	-	-
Water containing 5 mM ßCD (a)	0.096±0.04	4.17	P < 0.01
Water containing 2% PEG6000 (b)	0.162±0.02	7.04	P < 0.01
Water containing 5 mM ßCD and 2% PEG6000 (ab)	0.219±0.05	9.52	P < 0.01
Water containing 2% PVP ( c)	0.358±0.02	15.57	P < 0.01
Water containing 5 mM ßCD and 2% PVP (ac)	0.522±0.03	22.70	P < 0.01
Water containing 2% PEG6000 and 2% PVP (bc)	0.482±0.07	20.96	P < 0.01
Water containing 5 mM ßCD, 2% PEG6000 and 2% PVP (abc)	0.587±0.06	25.52	P < 0.01

Table 3: Solubility of VST in Various Fluids as per 2³ Factorial Study

Valsartan
Fluids	Solubility (mg/ml) (n=5) (x±sd)	Increase in Solubility (ratio)	Significance
Distilled water (1)	0.303±0.02	-	-
Water containing 5 mM ßCD (a)	0.389±0.06	1.28	P < 0.01
Water containing 2% PEG6000 (b)	0.408±0.01	1.35	P < 0.01
Water containing 5 mM ßCD and 2% PEG6000 (ab)	6.487±0.03	21.41	P < 0.01
Water containing 2% PVP ( c)	0.563±0.05	1.86	P < 0.01
Water containing 5 mM ßCD and 2% PVP (ac)	2.912±0.03	9.61	P < 0.01
Water containing 2% PEG6000 and 2% PVP (bc)	2.034±0.02	6.71	P < 0.01
Water containing 5 mM ßCD, 2%PEG6000 and 2% PVP (abc)	5.543±0.02	18.29	P < 0.01

First, CCX solubility was highly improved by PEG 6000 (2.24ratio), PVP (1.83ratio), then ß-CD (1,34ratio) individually. ßCD in combination with PEG 6000 has given highest enhancement (4.95ratio).

FSD solubility was improved by PVP (15.57ratio), by PEG 6000(7.04 ratio) then by ß-CD (4.17 ratio) individually. ß-CD in combination with PEG 6000 and PVP gave respectively (9.52ratio) and(22.70 ratio) increase in the solubility of FSD. ß-CD in combination with PEG 6000 and PVP has given highest enhancement (25.52 ratio) in the solubility of FSD.

Finally, VST solubility was highly improved by PVP ( 1,86 ratio), by PEG 6000 (1,35 ratio) then by ß-CD (1,28ratio) individually. ßCD in combination with PEG 6000 has given highest enhancement (21, 41ratio), followed by ßCD-PEG6000-PVP combination (18,29 ratio) among combined effects.

Dissolution Results:

Table 4: Dissolution rates of FSD – ßCD complex systems prepared as per 2³Factorial Study

Complex	Composition	Dissolution Rate /min	Increase in Dissolution Rate (ratio)
F1	CCX	1.23	-
Fa	CCX-ßCD (1:2)	1.79	1.46
Fb	CCX-PEG 6000 (2%)	2.95	2.40
Fab	CCX-ßCD (1:2) - PEG 6000 (2%)	12.34	10.03
Fc	CCX-PVP (2%)	1.93	1.57
Fac	CCX- ßCD (1:2)-PVP (2%)	5.77	4.69
Fbc	CCX-PEG 6000 (2%)-PVP (2%)	2.87	2.33
Fabc	CCX- ßCD (1:2)-PEG 6000 (2%)-PVP (2%)	4.92	4.00

Table 5: Dissolution rates of CCX– ßCD complex systems prepared as per 2³Factorial Study

Complex	COMPOSITION	Dissolution Rate /min	Increase in Dissolution Rate (ratio)
F1	FSD	1.22
Fa	FSD-ßCD (1:2)	10.46	8.57
Fb	FSD-PEG 6000 (2%)	8.56	7.02
Fab	FSD-ßCD (1:2) - PEG 6000 (2%)	18.83	15.43
Fc	FSD-PVP (2%)	1.99	1.63
Fac	FSD- ßCD (1:2)-PVP (2%)	25.69	21.06
Fbc	FSD-PEG 6000 (2%)-PVP (2%)	1.89	1.55
Fabc	FSD- ßCD (1:2)-PEG 6000 (2%)-PVP (2%)	27.59	22.61

Table 6: Dissolution rates of VST – ßCD complex systems prepared as per 2³Factorial Study

Complex	COMPOSITION	Dissolution Rate /min	Increase in Dissolution Rate (ratio)
F1	VST	4.24
Fa	VST-ßCD (1:2)	4.57	1.08
Fb	VST-PEG 6000 (2%)	7.45	1.76
Fab	VST-ßCD (1:2) - PEG 6000 (2%)	7.58	1.79
Fc	VST-PVP (2%)	15.03	3.54
Fac	VST- ßCD (1:2)-PVP (2%)	5.72	1.35
Fbc	VST-PEG 6000 (2%)-PVP (2%)	5.22	1.23
Fabc	VST- ßCD (1:2)-PEG 6000 (2%)-PVP (2%)	6.24	1.47

In tables 4, 5, 6 Anova analysis of dissolution rates shows that individual main effects of ßCD, PEG 6000 and PVP and their combined effects to improve dissolution rate (K1) were highly significant (P < 0.01) for each API studied,

Table 4 shows CCX dissolution rate results:ßCD increased dissolution rate by a 1.46 ratio in the dissolution rate, and in combination with PVP and PEG 6000 gave respectively 4.69 ratio and 10.03 ratio increase in the dissolution rate of CCX. The highest enhancement of dissolution rates was recorded for CCX-ßCD (1:2) - PEG 6000 (2%) combination (10.03 ratio).

In table 5, ßCD increased FSD dissolution rate by a 8.57ratio increase in the dissolution rate, and in combination with PVP and PEG 6000 gave respectively 21.06 ratio and 15.43 ratio increase in the dissolution rate of FSD. The highest enhancement of solubility were recorded for FSD- ßCD (1:2)-PEG 6000 (2%)-PVP (2%) combination (22,61 ratio).

Finally in Table 6, VST dissolution rate were improved by in the one hand ßCD alone that gave a 1.08 ratio increase in the dissolution rate, and in combination with PVP and PEG 6000 it gave respectively 1.35 and 1.79 ratio. The highest enhancement for solubility was recorded for VST-PVP (2%) combination (3.54 ratio).

Overall, PEG 6000 was found to be a good solubilizer alone and in combination with ßCD and PVP to enhance the solubility and dissolution rate of the selected three BCS class II and IV drugs.

CONCLUSION:

All beta CD PEG 6000 and PVP enhanced VST, FSD and CCX solubilities alone and in binary and ternary combination.Anova analysis showed that individual and combined effects of ß-CD, PEG 6000 and PVPon enhancing the three drugs’ solubilities were highly significant (P<0.01).Beta CD, PEG 6000 and PVP enhanced each CCX, FSD and VSR solubility used individiually, on binary and ternary combinations.

Hence, PEG 6000 is a suitable solubilizer alone and in combination with ßCD and PVP to enhance the solubility and dissolution rate of the selected three BCS Class II and IV drugs.

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Received on 28.08.2023 Modified on 22.11.2023

Research J. Pharm. and Tech 2024; 17(6):2639-2643.

DOI: 10.52711/0974-360X.2024.00413