Comparison of In vitro Dissolution Tests of five brands of Diclofenac Sodium delayed release tablets in Moroccan market

 

Ismail Bennani^1,2, Hajar Benhaddou³, Ali Cherif Chefchaouni^3,4, Younes Rahali^3,4,

Madiha Chentoufi Alami⁵, Aicha Fahry³, Yassir El Alaoui^3,4, Abdeslam El Kartouti¹,

Youssef Hafidi², Abdelkader Laatiris³, Nawal Cherkaoui³

¹Department of Pharmacy, Faculty of Medicine, Pharmacy and Dental Medicine of Fez,

Sidi Mohamed Ben Abdellah University, Fez, Morocco.

²Department of Pharmacy, Hassan II University Hospital of Fez, Morocco.

³Faculty of Medicine and Pharmacy, Mohammed V University of Rabat, Rabat, Morocco.

⁴Ibn Sina University Hospital Center, Rabat, Morocco.

⁵Faculty of Medicine and Pharmacy of Tangier, Abdelmalek Essaâdi University.

 

ABSTRACT:

This study aims to evaluate the similarity of in-vitro dissolution profiles, of commercially available generics of diclofenac sodium delayed-release tablets, of 25mg strength, with the innovator brand in Moroccan Market. Dissolution profiles for five brands were determined using the paddle method from the United States Pharmacopoeia. For the aptitude verification of the method, in our experimental conditions, linearity and accuracy tests were performed. The rate of dissolution was determined by Ultra-Violet Spectroscopy at 276nm. The assessment between the generics and the brand medicine was carried out under the similarity factor approach. We also presented an overview of the dissolution principles of tablet dosage form, and the pharmacopoeia dissolution test recommendations in our case. To compliance with US pharmacopoeia specifications, the rate of dissolution should be not more than 10% after 2hours in the acid stage, and not less than 75% at 45 minutes in the buffer stage. Furthermore, two dissolution profiles are considered similar when the f2 value is ≥50. According to routine quality control, evaluating the rate dissolution at the final point, all the generic medicines marketed in Morocco, meet the specification of the dissolution testing. However, using the comparison of dissolution profiles, only generic-2 is interchangeable with the innovator brand.

 

 

INTRODUCTION: 

The Dissolution Testing (DT) is established valuable statistical quality-control tool. It is widely used for developing new drug products¹, determining the long-term stability and shelf life of a dosage form², allow evaluation of drug release and facilitate appropriate selection of excipients during formulation development for solid oral forms³, and assessing the impact of post-approval changes in the manufacturing process.

 

 

In preformulation, especially in the case of poorly soluble substances, it is important to know the dissolution rate of the active pharmaceutical ingredient to consider solutions for optimisation of the drug formulation. For quality control in routine, the specification for solid oral dosage forms normally includes a test to measure release of the drug substance from the drug product⁴. The dissolution testing allows monitoring the batch-to-batch consistency. It is also used to verify that the rate of release of the active substance remains constant during storage. During the development of a medicinal product, a dissolution test is used as a tool to identify formulation factors that are influencing the availability of the drug⁵. This control is required for pharmaceutical laboratories, to obtain Marketing Authorization (MA). For generic drugs the applicant should provide also the comparison of the dissolution profiles between their generic and the brand medicine. 

 

Diclofenac is a nonsteroidal anti-inflammatory drug with both analgesic and antipyretic activities. It is commonly used in the treatment of rheumatic disorders, and is available in a number of 25mg, 50mg or 75mg preparations. The drug is a BCS class II weak acid and exhibits pH-dependent solubility in the physiological pH range which increases with increasing pH value^6,7, and it is a poorly water soluble drug⁸. In the Moroccan market, once of most popular non-steroidal anti-inflammatory drugs, diclofenac sodium is available on delayed-release tablets to different strengths 25 and 50mg. For our assessment, we chose the most discriminating, the lower dose.

 

The objective of this study is to perform an in vitro dissolution profile comparison between the reference drug and 4 of its generic diclofenac sodium delayed release (DSDR) tablets.

 

MateriAl and Methods:

Chemicals and reagents:

The reference drug as well as 4 generic drugs (named generic 1, generic 2, generic 3, generic 4) of diclofenac was purchased from pharmacies. Diclofenac Sodium Working Standard (purity = 100.76%; Water content = 0.4%) was provided by the National Drug Control Laboratory (LNCM; Rabat, Morocco).

 

Standard preparation:

The stock standard solution (1mg mL-1) was prepared by dissolving 100mg equivalent of diclofenac sodium reference standard in 100mL of distilled water. Six different concentration levels of calibration solutions (15, 30, 50, 90, 100 and 120% of label claim) were freshly prepared by diluting appropriate volumes of the stock standard solution into appropriate volumetric flasks.

 

Dissolution testing:

Dissolution rate studies of the Diclofenac Sodium tablets were carried out according to the USP paddle methodof DSDR tablets monograph in two stages. Firstly in acid stage during 2hours, then in buffer stage during 75min. (Table I).At each time point (Table I), a 5ml sample of the dissolution medium in each vessel was taken with a syringe, filtered through a 0.45µm filter and analyzed with a JENWAY 6305 UV-Visible spectrophotometer at 276nm. The rates of dissolution required at the specified times by USP monograph were: not more than 10% after 2hours in the acid stage and not less than 75% at 45minutes in the buffer stage.

 

Dissolution profile comparison: Similarity factor approach:

The assessment of the similarity of dissolution profiles between the brand medicines and the generic drugs, were evaluated with the fit-factor method. Two factors, f₁ and f₂, were calculated, given by the following equations:

·       The similarity factor – f₂, that measures the closeness between the two profiles.And the difference factor – f₁², which is a measure of the relative error between the two curves studied :. Where (n) is the number of time points, (t)mean percent reference drug dissolved at time (t) and (t) mean percent test drug dissolved at time (t). An f₂ values between 50-100, and f₁ value close to 0 up to 15, suggest that the two dissolution profiles are similar.It should be noted that the practical part of this work took place at the level of the laboratory of galenic pharmacy at the Faculty of Medicine and Pharmacy of Rabat, while the statistical analysis and the writing is done at the level of the department of pharmacy of the Faculty of Medicine and Pharmacy of Fez.

 

Results and Discussion:

1.     Tablet dissolution basic principles:

For a tablet, dissolution involves the interaction of solid API, of the solid dosage form, and the dissolution medium, upon specific experimental conditions.  Generally, active pharmaceutical ingredients (API) are mixed with inactive excipients and pressed into a tablet. In the body, the API must be “in solution” before it can be absorbed by the blood and ultimately carried to the receptor site to render a therapeutic effect. Dissolution is the process by which that active ingredient enters into a solvent to yield a solution ⁹.  Firstly, solute molecules are disintegrated and solvent molecules dispersed to form a cavity. This one is filled with disintegrated solute molecules one by one to complete the process of dissolution, as shown in figure 1. All steps may be occurring simultaneously as shown in the diagram of figure 2¹⁰.

 

2.     Pharmacopoeia dissolution testing recommendations:

In the official pharmacopoeias, Unites State Pharmacopoeia (USP), European Pharmacopoeia (EP), the most commonly employed dissolution test methods are the basket method (Apparatus 1) and the paddle method (Apparatus 2) (figure2). The apparatus consists of cylindrical vessels, with a hemispherical bottom and a capacity of 1 L. Those are partially immersed in a thermostatically-controlled water bath with a stirring element in the centre (basket or paddle)¹¹.

3.     Aptitude Verification of the Method:

Analytical validation of the compendial methods is not required, only an aptitude verification is sufficient¹².

 

Linearity:

The linearity is the ability (within a given range) to obtain test results which are directly proportional to the concentration (amount) of analyte in the sample¹³. The linearity criteria must only be applied to the results [calculated concentration=f (introduced concentration)], not to the responses [signal=f (introduced concentration)]¹⁴.

 

The ICH-Q2 guideline recommends a minimum of 5 points concentrations. Prepared directly on the drug substance by dilution of a standard stock solution, and/or by separate weighings of synthetic mixtures of the drug product components. Three analyses for each point are generally utilized. Linear regression analysis is required including: the correlation coefficient, the y-intercept, the slope of the regression line, the residual sum of squares and a plot of the data. The table II, summarize the linearity results obtained and the plot of results is represented in figure 4. The correlation coefficient must be ≥ 0,99 and % y-intercept NMT[1] 2% to the analyte target. Our data shows an acceptable correlation coefficient and % y-intercept which are respectively (0,998) and (-1,49E-02).

 

4.     Similarity dissolution profiles evaluation:

- Regulatory requirements:

The dissolution profile comparison may be carried out using model independent approach of a similarity factor. It is recommended by many global regulatory authorities as a means to demonstrate dissolution similarity¹⁵. 12 dosage units at least is required each of test and reference products. For profiles obtained in multiple media, similarity should be evaluated in each individual medium. It is recommended that only one point past the plateau of the profiles be used in calculating the f₂ value. To allow the use of mean data, the coefficient of variation should demonstrate a low variability: not more than 20percent at the early time-points, and not more than 10percent at other time points¹⁶. Where more than 85% of the drug is dissolved for both test and reference products within 15 min, dissolution profiles may be accepted as similar without further mathematical evaluation¹⁶.

 

- Comparison of dissolution profiles of commercially available DSDR 25mg tablets in Moroccan market:

In general, studies investigating or comparing the dissolution profiles of commercially marketed drugs have already been conducted^17-19. All DSDR reference and generics tablets, did not dissolve in acid stage, and started to dissolve at 10min in buffer stage to reached almost 100% at 45min, as illustrated in the dissolution profiles (figure 5). Considering the routine quality control, the rate of dissolution at the final point, in both stages, are in compliance with the European and US Pharmacopoeias requirements (<10% in acid stage and ≥80% or 75% in buffer stage). Nevertheless, comparing the dissolution profiles, the interpretation differs. In fact, the evaluation of the similarity profiles using f₁-f₂ factors, demonstrate that only generic-2 dissolution profile is similar. And the factor values, similarity factor f₂=75,86% and difference factor f₁=5%, meet the regulatory requirements. The comparative dissolution of the other generic medicines shows a wide range of variability. The following table summarized the results of calculated f1 and f2 factors with the coefficients of variation of tested drugs (Table II). Several factors ⁵can influence the profile dissolution, among these we find:

 

·       Drug excipient interaction: this interactivity such as any unit operation such as milling, mixing, blending, drying and granulation result change in dissolution.

·       Diluents are commonly added in tablet and capsules influence the dissolution rate of drug, for examples: starch, lactose and microcrystalline cellulose.

·       Lubricants: they increase the dissolution rate of poorly soluble drug. This is due to the lowering of interfacial tension increase effective surface area which in turn results in faster dissolution rate.

 

Delayed-release tablets are intended to resist acid gastric fluid but disintegrate in intestinal fluid. This is achieved by using coating substances such as cellacefate (cellulose acetate phthalate) and anionic copolymers of methacrylic acid and its esters. These formulations also include in their formulation a copolymer of methacrylic acid (Eudragit LD 30) which is responsible for the delayed release of the active ingredient.  On the other hand, these drugs that have obtained the MA have necessarily presented a study with satisfactory similarity dissolution profile with the brand medicine at submission. This underlines the importance of the quality post-market surveillance for drugs to monitor compliance with the marketing authorisation. The latter is the process by which a drug product is evaluated for safety and compliance with standards established by the regulatory authority, taking into account patient and public safety²⁰.

 

CONCLUSION:

DT involves dissolving the active substance contained in a solid dosage form of a drug, under controlled conditions (T°37±0.5°C; specified pH and medium, apparatus, etc.). With collection and analysis of a sample(s), at final point time, in routine control, or during regular time point intervals, in dissolution profile evaluation. It has emerged as a very important tool in the generic pharmaceutical industry. In approval of generic drug products, the dissolution testing is recommended for stability and quality control. It may be used to waive in vivo bioequivalence study requirements ²¹

 

 

Figure 1: Interaction between solute API and solvent in process dissolution.

 

 

Figure 2: Disintegration, deagregation, and the solution process

 

Figure 3. Basket versus paddle stirring element of the apparatus for dissolution testing²².

 

 

Figure 4: Linearity plot of results.

 

 

Figure 5: Dissolution profiles DSDR 25mg

Table I Dissolution Testing Parameters according to the USP

	Dissolution medium	Rotation speed (rpm)	Sampling time points (min)
Acid stage	900 mL of HCl 0.1N at 37±0.5°C.	50	30, 60, 90 and 120
Buffer stage	900 mL of phosphate buffer pH 6.8 at 37±0.5°C.	50	10, 20, 30, 45, 60 and 75

 

Table: II: Linearity Data-Sheet

		Absorbance (Response)			Obtained amount mg (Result)			Mean	SD	RSD %
Introducedamount		measure 1	measure 2	measure 3	result  1	result 2	result 3
mg	%
0	0%	-	-	-	-	-	-	-	-	-
3,8	15%	0,124	0,122	0,126	4,3	4,2	4,3	4,3	0,05	1,2%
7,5	30%	0,215	0,217	0,214	7,4	7,4	7,3	7,4	0,06	0,9%
12,5	50%	0,342	0,346	0,346	11,7	11,7	11,7	11,7	0,01	0,1%
22,5	90%	0,670	0,679	0,672	22,7	22,9	22,7	22,7	0,10	0,4%
25,0	100%	0,738	0,749	0,756	25,0	25,2	25,5	25,2	0,23	0,9%
30,0	120%	0,889	0,889	0,884	30,1	29,9	29,8	29,9	0,17	0,6%
Sloperesponse		0,0297	0,0299	0,0298	Equation for regression line :  y = 0,0298x - 0,0038
y-interceptresponse		-0,0039	-0,0044	-0,0029	Correlation coefficient (r2) = 0,9986
					Residualsum of squares = 1,0815

 

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Accepted on 09.08.2023           © RJPT All right reserved

Research J. Pharm. and Tech 2024; 17(2):631-635.