INTRODUCTION:

According to Data Bridge Market Research the topical use acne treatment market is attaining growth in developing nations during the upcoming period of 2019-2026 due to several factors such as increasing prevalence of acne diseases, availability of skin care products, rising disposable income and increasing demand of the population to spend on facial appearance.^1,2

Even though some information about an innovator drug product’s API and excipient components can be found in some common sources such as product information brochures, Orange book, Physician’s Desk Reference, or FDA’s Website one can be more confident and reliable about the generic product’s performance by developing formula that is as qualitatively and quantitatively similar to the reference listed drug (RLD) as possible.³

Deformulation consists of separation, identification and quantitation of individual components or ingredients present in a drug product. Deformulation develops the most essential information needed for generics drug development since a generic drug formulation must meet bioequivalence as the brand name drug (Reference Listed Drug) for which the generic is to be substituted. For a generic to be bioequivalent with RLD, it must meet Q1, Q2 and Q3 sameness i.e. similar ingredients, quantities and physicochemical properties respectively. Pharmaceutical deformulation can be a complex process and it depends on the composition of the drug which has to be deformulated. Step 1 of deformulation begins with; identification of the excipients with respect to its grade used in Reference Listed Drug product which is used to verify label claims and assists a chemist with the formulation. 2^nd and 3^rd level of deformulation is to quantitate the excipients in the formulation.^4,5

Various factors such as fluctuating hormone levels, unhygienic lifestyle and excessive production of oil from sebaceous gland have increased the prevalence of acne.

Dapsone [bis (4-aminophenyl) sulphone] is used in the treatment of leprosy, acne vulgaris, dermatitis herpetiformis and other skin diseases. It is white or creamy-white, crystalline powder. It is freely soluble in ethanol (95 %) and acetone; practically insoluble in water.¹⁰ It is odorless and slightly bitter in taste.^6-9

Fig. 1: Structure of Dapsone

Dapsone is available in both topical and oral pharmaceutical formulations. Oral administration of dapsone is less due to its severe adverse effects.¹⁰

Determination of composition of Dapsone gel of different manufacture can be done by using various methods such as LC-MS, HPLC, FTIR, and GC.¹¹

Though generics companies have used reverse engineering for quite some time, the topic is hardly discussed in the public literature. Hence the aim of study is to determine the composition of commercial available dapsone gel by analytical method using deformulation (reverse engineering) technique.

MATERIAL AND METHODS:

Materials:

Chemicals used:

Pure API sample of Dapsone was a gift sample from Aadhaar Life Sciences Pvt. Ltd., MIDC Solapur, Maharashtra. Marketed Dapsone gel of 5%w/w of Cipla was purchased from local market. And other chemicals such as DGME, Methyl paraben, water, Sodium hydroxide and Carbopol 980 of AR grade were used.

Instruments used:

Deformulation of marketed Dapsone gel formulation was done by different analytical methods using GC-FID, Brookfield viscometer, Karl Fischer Titration apparatus, pH meter; Acid- base titration, etc.A gas chromatography system (AGILENT 7890), analytical balance (ACZET CY224C), sonicator (Labman) and vortex mixer (REMI) were also used in this study.

Methods:

Preliminary Analysis of Commercial available Dapsone Gel:

a. Description:

The marketed formulation of Dapsone gel (Acnedap) was observed for its color and texture.

b. Microscopic Observation:

The marketed formulation of Dapsone gel was observed under compound microscope.

c. Viscosity:

The measurement of viscosity of the marketed Dapsone gel was performed by using Brookfield digital viscometer equipped with spindle. The apparent viscosity was measured at shear rate of 50rpm and room temperature after a 3 min rest time.

d. pH analysis:

The pH of marketed Dapsone gel was determined by using calibrated digital pH meter. The glass electrode was dipped in a beaker containing gel and left for about 15 min for attaining equilibrium for measurement. The analysis of pH was done in triplicate and average was calculated.

Identification and Quantification composition of Marketed Formulation of Dapsone Gel:

Dapsone:

Dapsone was identified by its physicochemical properties such as color, microscopic evaluation, melting point, etc. and also the qualitative and quantitative data is provided at label claim. The quantitative analysis of Dapsone can be carried out by using HPLC method.

DGME:

Diethylene glycol monoethyl ether was identified and quantified by using GC-FID method using nitrogen as acarrier gas.

Methyl paraben:

The qualitative and quantitative data was obtained from product information brochures. Presence of methyl paraben was provided on the label claim and it is commonly used preservative in pharmaceuticals.

Carbopol 980:

Presence of carbopol was identified by checking the viscosity of the marketed Dapsone gel formulation. As both Carbopol 940 P NF and Carbopol 980 polymers being used in topical gel formulation it was difficult task for determining its grade. Only the difference between Carbopol 940 P NF and Carbopol 980 is the solvent used in their manufacturing. Hence, the grade was checked by identifying residual solvent in it.

Water:

Water content of the Dapsone gel was determined by Karl Fischer Titration. Moisture content was determined by calculating mean of triplicate samples of marketed Dapsone gel after Karl Fischer titration.

Sodium hydroxide:

1gm of gel was weighed accurately in a conical flask, then dissolved in acetonitrile (ACN) and then titrated the resultant solution against hydrochloric acid (HCl) and the concentration used in marketed gel formulation was detected by further calculation.

RESULTS AND DISCUSSION:

Preliminary Analysis of Commercial available Dapsone Gel:

Preliminary analysis of Commercial Available Dapsone Gel such as color, texture and its label confirms the identification of Acnedap Gel. The marketed formulation of Dapsone gel was found to be white with smooth texture.

Methods Used for Qualitative and Quantitative Analysis of Composition of Marketed Dapsone gel 5%w/w of Cipla (Acnedap Gel):

Literature survey plays the key role in reverse engineering of product, and sound knowledge of formulation development makes the process easier.

DGME:

Qualitative and quantitative analysis of DGME was carried out by using GC-FID method. And the concentration of DGME was found to be 25% of marketed gel formulation.

Fig. 2: Chromatogram of marketed dapsone gel solution

Methyl paraben:

Qualitative and Quantitative data methyl paraben was obtained from label claim as product information brochure. And it was found to be 0.2% of marketed gel formulation.

Carbopol 980: Determination of Viscosity and Grade of Marketed Dapsone Gel by Brookfield Viscometer:

Carbopol 980 was determined from viscosity and residual solvent of marketed Dapsone gel formulation. Grade of Carbopol was determined by residual solvent method. The presence of cyclohexane and ethyl acetate in residual solvent confirms the grade of carbopol (i.e. Carbopol 980) used in the marketed gel formulation. And the concentration of carbopol 980 was found to be 0.5% of marketed gel formulation.

Table 1: Viscosity of Marketed Dapsone Gel

Parameter	Observation
Viscosity	42000 Pa.s
Grade	Carbopol 980

Water: Karl-Fischer Titration for Determination of Water Content in Marketed Gel Formulation:

Water Content of marketed formulation of Dapsone Gel was determined by Karl FischerTitration method and it was 69.2% of marketed gel formulation.

Table 2: Moisture Content in Dapsone gel

Sr. No.	Weight of Gel Product (mg)	Moisture Content (%)
1	24.7	66.97
2	14.0	71.42
3	19.2	69.94

Sodium hydroxide:

The concentration of sodium hydroxide was determined by acid- base titration. And it was found to be 0.1% of the marketed gel formulation.

Determination of pH of Marketed Dapsone Gel Formulation:

The pH of marketed gel was determined by using pH meter.

Table 3: pH of Marketed Dapsone Gel

Sr. No.	pH
1	5.5
2	5.5
3	5.4
Mean	5.5

Determination of Composition of Commercial Formulation of Dapsone Gel (Acnedap Gel):

Table 4: Results of Quantitation of API and excipients of marketed Acnedap Gel

Sr. No.	Ingredients	% Concentration
1	Dapsone	5
2	DGME	25
3	Methyl paraben	0.2
4	Carbopol 980	0.5
5	Water (q. s.)	69.2
6	Sodium hydroxide (q. s.)	0.1

CONCLUSION:

The study was aimed to determine the composition of marketed formulation of dapsone gel 5% by using different analytical methods. And thus the reverse engineering of marketed formulation of Dapsone gel was successfully performed, which was confirmed by conducting characterization of active and inactive ingredients present in innovator’s product by different analytical techniques. Based on the qualitative and quantitative data obtained by deformulation of marketed Dapsone Gel, generic Dapsone Gel can be prepared. The proposed analytical methods were found to be appropriate due to its simplicity, reliability and rapidness.

ACKNOWLEDGEMENT:

The authors express their sincere thanks to the D.S.T.S. Mandal’s College of Pharmacy, Solapur. The authors are also thankful to the Aadhaar Life Sciences Pvt. Ltd., MIDC Chincholi, Solapur for providing laboratory facilities and support.

CONFLICT OF INTEREST:

No conflict of interest.

REFERENCES:

1. Topical Use Acne Treatment Market- Global Industry Trends [Internet]. 2018 [Cited on 2019 July 16]. Available from: https://www.databridgemarketresearch.com/reports/global-topical-use-acne-treatment-market

2. ‌Global Market Insights [Internet]. 2018 [Cited on 2019 July 16]. Available from: https://www.gminsights.com/industry-analysis/ acne-medication-market

3. Reverse engineering of pharmaceuticals [Internet]. 2005 [Cited on 2019 July 16]. Available from: http://www.pharmtech.com/role-reverse-engineering-development-generic-formulations Deformulation [Internet]. 2018 [Cited on 2019 July 16]. Available from: https://eutechsci.com/deformulation-services/

4. How can Deformulation/Reverse Engineering Help Your Formulation [Internet]. 2018 [Cited on 2019 July 16]. Available from: https://www.pharmaexcipients.com/news/how-can-deformulation-reverse-engineering-help-your-formulation/

5. Equivalence of Locally Acting Drug Product [Internet]. [Cited on 2019 July 17]. Available from: https://www.fda.gov/media/91563/ download

6. Pharmaceutical reverse engineering [Internet]. [Cited on 2019 July 17]. Available from: https://www.avomeen.com/lifesciences-pharmaceutical-reverse-engineering-how-it-works/Reverse engineering [Internet]. [Cited on 2019 July 17]. Available from: https://www.quora.com/How-do-I-perform-reverse-engineering-in-pharmaceuticals

7. Indian Pharmacopoeia 2010. Vol. I: 154.

8. Indian Pharmacopoeia 2010. Vol. II: 1162.

9. Dapsone [Internet]. [Cited on 2019 July 17]. Available from: https://en.m.wikipedia.org/wiki/ File: Dapsone.svg

10. Pickert A, Raimer S. An evaluation of dapsone gel 5% in the treatment of acne vulgaris. Expert Opin Pharmacother. 2009; 10(9): 1515-1521.

11. Zahid Z, Furquan N, Sarfaraz K, Moizul H, Obaid S, Raheel K. Reverse engineering and development of generic Orlistat formulation. JIPBS. 2016; 3(4):17-25.

12. Mangesh B, Ashwini M and Shraddha P. Development of generic Dapsone gel 5% using QbD technique. WJPR. 2018; 7(13): 1005- 1024.

13. Ashish G and Kashimra P. Formulation, development and evaluation of antiacne gel. WJPPS. 2017; 6(8): 1664-1679.

14. Karl Fischer Titration [Internet]. [Cited on 2019 Oct 15]. Available from: https://en.m.wikipedia.org/wiki/Karl_Fischer_titration#:~: text=Karl%20Fischer%20titration%20is%20a,an%20automated%20Karl%20Fischer%20titrator.

15. Brookfield Viscometer [Internet]. [Cited on 2019 Oct 5]. Available from: https://www.ceramictestingequipment.co.uk/product.php? product=130

16. Carbopol Polymer Products [Internet]. [Cited on 2019 Oct 5]. Available from: https://www.lubrizol.com/Health/Pharmaceuticals /Excipients/Carbopol-Polymer-Products

17. Shin H and Jung D. Determination of icing inhibitors (ethylene glycol monoethyl ether and diethylene glycol monoethyl ether) in ground water by gas chromatography- mass spectrometry. Bull Korean Chem Soc. 2004; 25(6): 806-808.

Received on 10.10.2020 Modified on 30.10.2020

Res. J. Pharma. Dosage Forms and Tech.2021;13(1):19-22.

DOI: 10.5958/0975-4377.2021.00004.5