Diving into Batch-to-Batch Variability of Topical Products-a Regulatory Bottleneck



Following the recent European Medicine Agency (EMA) draft guideline on quality and equivalence of topical products, a modular framework for bioequivalence assessment is proposed, wherein the qualitative, quantitative, microstructure and product performance sameness is demanded to support generic applications. Strict regulatory limits are now imposed, but, the suitability of these limits has been subject of intense debate. In this context, this paper aims to address these issues by characterizing a panel of 8 reference blockbuster semisolid topical products.


For each product, three batches were selected and, whenever possible, batches retrieved from different manufacturing sites were considered. Product microstructure was evaluated in terms of globule size, pH, rheological attributes and, if required, the thermal behaviour was also assessed. Performance was evaluated through in vitro release testing (IVRT). Finally, an integrated multivariate analysis was performed to highlight the features that most contribute for product variability.


Marked differences were registered within reference products. Statistical analysis demonstrated that if EMA criteria are applied, none of the same product batches can be considered as equivalent. Rheological parameters as well as IVRT indicators account for the majority of batch-to-batch differences.


Semisolid dosage forms exhibit intrinsic variability. This calls for the attention to the need of establishing reasonable equivalence criteria applied to generic drug products.

Graphical abstract

This is a preview of subscription content, log in to check access.

Fig. 1
Fig. 2
Fig. 3
Fig. 4





Active pharmaceutical ingredient


Biopharmaceutical classification system






Clinical endpoint studies


Confidence intervals






Critical quality attributes


Coefficient of variation




European Medicine Agency




Storage modulus


Loss Modulus




Hierarchical cluster analysis


High performance liquid chromatography


In vitro permeation testing


In vitro release rate


In vitro release testing


Linear viscoelastic region


Molecular weight




Non-steroid anti-inflammatory drugs


Phosphate buffered ased saline


Principal component analysis

Q final point:

Cumulative amount of drug released at the end of IVRT

Q initial point:

Cumulative amount of drug released in the beginning of IVRT


Statistical significance




Topical generic product


US Food and Drug Administration


United States Pharmacopeia


Vertical diffusion cell


  1. 1.

    Mordor I. Dermatological Therapeutics Market | Growth, Trends, and Forecast (2019–2024) [Internet]. 2019 [cited 2019 Oct 29]. Available from: https://www.mordorintelligence.com/industry-reports/dermatological-therapeutics-market

  2. 2.

    Patere S, Newman B, Wang Y, Choi S, Vora S, Ma AWK, et al. Influence of manufacturing process variables on the properties of ophthalmic ointments of tobramycin. Pharm Res Pharmaceutical Research. 2018;35.

  3. 3.

    Mordor I. Topical Analgesic Market | Growth, Trends, and Forecast (2019–2024) [Internet]. 2019 [cited 2019 Nov 2]. Available from: https://www.mordorintelligence.com/industry-reports/topical-analgesic-market

  4. 4.

    Mordor I. Anti-fungal Drugs Market | Growth, Trends, and Forecast (2019–2024) [Internet]. 2019 [cited 2019 Nov 2]. Available from: https://www.mordorintelligence.com/industry-reports/anti-fungal-drugs-market

  5. 5.

    Miranda M, Sousa JJ, Veiga F, Cardoso C, Vitorino C. Bioequivalence of topical generic products. Part 1: where are we now? Eur J pharm Sci [internet]. Elsevier; 2018;123:260–7. Available from: https://doi.org/10.1016/j.ejps.2018.07.050, 2018

  6. 6.

    Miranda M, Cardoso C, Vitorino C. Quality and Equivalence of Topical Products: A Critical Appraisal. Eur J Pharm Sci [Internet]. 2019 [cited 2019 Nov 2];105082. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0928098719303550

  7. 7.

    Yacobi A, Shah VP, Bashaw ED, Benfeldt E, Davit B, Ganes D, et al. Current challenges in bioequivalence, quality, and novel assessment technologies for topical products. Pharm Res. 2014;31:837–46.

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  8. 8.

    Braddy AC, Davit BM, Stier EM, Conner DP. Survey of international regulatory bioequivalence recommendations for approval of generic Topical Dermatological drug products. AAPS journalAaps J. 2015;17:121–33.

    Article  Google Scholar 

  9. 9.

    Miranda M, Sousa JJ, Veiga F, Cardoso C, Vitorino C. Bioequivalence of topical generic products. Part 2. Paving the way to a tailored regulatory system. Eur. J. Pharm. Sci. 2018.

  10. 10.

    Soares KCC, de Souza WC, Texeira L d S, da Cunha-Filho MSS, Gelfuso GM, Gratieri T. Comparison of Clobetasol propionate generics using simplified in vitro bioequivalence method for Topical drug products. Curr Drug Deliv. 2017;15:998–1008.

    Article  Google Scholar 

  11. 11.

    EMA. Draft guideline on quality and equivalence of topical products [Internet]. 2018. Available from: www.ema.europa.eu/contact

  12. 12.

    Fernández-Campos F, Obach M, Moreno MC, García A, González J. Pharmaceutical development of a generic corticoid semisolid formulation. J Drug Deliv Sci Technol [Internet]. 2017;42:227–36 Available from: http://linkinghub.elsevier.com/retrieve/pii/S1773224717300825.

    Article  Google Scholar 

  13. 13.

    Sinamora P. In vitro bioequivalence data for a Topical product: chemistry review perspective. Maryland: FDA Work bioequivalence Test Top drug Prod; 2017.

    Google Scholar 

  14. 14.

    Roberts M, Mohammed Y, Namjoshi S, Jung N, Chaitanya K, Cheruvu S, et al. Correlation of physicochemical characteristics and in vitro permeation test (IVPT) results for acyclovir and metronidazole topical products FDA workshop on bioequivalence testing of Topical drug products. Maryland: FDA Work bioequivalence Test Top drug Prod; 2017.

    Google Scholar 

  15. 15.

    Chang R-K, Raw A, Lionberger R, Yu LX. Generic development of topical dermatologic products: formulation development, process development, and testing of topical dermatologic products. AAPS J [Internet]. 2013;15:41–52 Available from: http://www.springerlink.com/index/10.1208/s12248-012-9411-0%5Cnpapers3://publication/doi/10.1208/s12248-012-9411-0.

    CAS  Article  Google Scholar 

  16. 16.

    Murthy SN. Characterizing the critical quality attributes and in vitro bioavailability of acyclovir and metronidazole Topical products. Maryland: FDA Work bioequivalence Test Top drug Prod; 2017.

    Google Scholar 

  17. 17.

    Raghavan L, Brown M, Michniak-Kohn B, Ng S, Sammeta S. In vitro release tests as a critical quality attribute in Topical product development. 2019

  18. 18.

    Shah VP, RǍdulescu FŞ, Miron DS, Yacobi A. Commonality between BCS and TCS. Int J Pharm. 2016;509:35–40.

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  19. 19.

    Qwist PK, Sander C, Okkels F, Jessen V, Baldursdottir S, Rantanen J. On-line rheological characterization of semi-solid formulations. Eur J pharm Sci [internet]. Elsevier B.V; 2019;128:36–42. Available from: https://doi.org/10.1016/j.ejps.2018.11.014, 2019.

  20. 20.

    Bostijn N, Van Renterghem J, Vanbillemont B, Dhondt W, Vervaet C, De Beer T. Continuous manufacturing of a pharmaceutical cream: investigating continuous powder dispersing and residence time distribution (RTD). Eur J pharm Sci [internet]. Elsevier B.V; 2019;132:106–17. Available from: https://doi.org/10.1016/j.ejps.2019.02.036, 2019.

  21. 21.

    van Heugten AJP, Braal CL, Versluijs-Helder M, Vromans H. The influence of cetomacrogol ointment processing on structure: a definitive screening design. Eur J Pharm Sci. 2017;99:279–84.

    Article  PubMed  Google Scholar 

  22. 22.

    Sayeed-Desta N, Pazhayattil AB, Collins J, Chen S, Ingram M, Spes J. Assessment methodology for process validation lifecycle stage 3A. AAPS PharmSciTech [internet]. AAPS PharmSciTech. 2017;18:1881–6. Available from. https://doi.org/10.1208/s12249-016-0641-9.

    Article  PubMed  Google Scholar 

  23. 23.

    Zarmpi P, Flanagan T, Meehan E, Mann J, Fotaki N. Biopharmaceutical aspects and implications of excipient variability in drug product performance. Eur J Pharm Biopharm [Internet]. Elsevier; 2017 [cited 2019 Feb 20];111:1–15. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0939641116305604

  24. 24.

    Bao Q, Morales-Acosta MD, Burgess DJ. Physicochemical attributes of white petrolatum from various sources used for ophthalmic ointment formulations. Int J pharm [internet]. Elsevier; 2020;583:119381. Available from: https://doi.org/10.1016/j.ijpharm.2020.119381, 2020.

  25. 25.

    Hauck WW, Shah VP, Shaw SW, Ueda CT. Reliability and reproducibility of vertical diffusion cells for determining release rates from semisolid dosage forms. Pharm Res. 2007;24:2018–24.

    CAS  Article  PubMed  Google Scholar 

  26. 26.

    Miranda M, Pais AACC, Cardoso C, Vitorino C. aQbD as a platform for IVRT method development–A regulatory oriented approach. Int J Pharm [Internet]. 2019;118695. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0378517319307409

  27. 27.

    Clares-Naveros B, Suñer-Carbó J, Calpena-Campmany A, Rodriguez-Lagunas M, Halbaut-Bellowa L, Zamarbide-Losada J, et al. Biopharmaceutical development of a Bifonazole multiple emulsion for enhanced epidermal delivery. Pharmaceutics. 2019;11:66.

    Article  PubMed Central  Google Scholar 

  28. 28.

    Filipovic M, Lukic M, Djordjevic S, Krstonosic V, Pantelic I, Vuleta G, et al. Towards satisfying performance of an O/W cosmetic emulsion: screening of reformulation factors on textural and rheological properties using general experimental design. Int J Cosmet Sci. 2017;39:486–99.

  29. 29.

    Mezger TG. The rheology handbook. Int. J. Product. Perform. Manag. 2010.

  30. 30.

    Li C, Liu C, Liu J, Fang L. Correlation between rheological properties, in vitro release, and percutaneous permeation of tetrahydropalmatine. AAPS PharmSciTech. 2011;12:1002–10.

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  31. 31.

    USP. Topical and Transdermal Drug Products — Product Performance Tests. Pharmacopeial forum [Internet]. 2009;35:12–28. Available from: http://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/transdermalGenChapter725.pdf

  32. 32.

    Miranda M, Cardoso C, Vitorino C. Fast Screening Methods for the Analysis of Topical Drug Products. Process 2020, Vol 8, Page 397. Multidisciplinary Digital Publishing Institute; 2020;8:397.

  33. 33.

    Krishnaiah YSR, Xu X, Rahman Z, Yang Y, Katragadda U, Lionberger R, et al. Development of performance matrix for generic product equivalence of acyclovir topical creams. Int J pharm [internet]. Elsevier B.V.; 2014;475:110–22. Available from: https://doi.org/10.1016/j.ijpharm.2014.07.034, 2014.

  34. 34.

    FDA. Guidance for industry: nonsterile semisolid dosage forms : scale-up and postapproval changes : chemistry, manufacturing, and controls : in vitro release testing and in vivo bioequivalence documentation. [Internet]. 1997. Available from: http://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=edsgpr&AN=gprocn587646051

  35. 35.

    Tiffner KI, Kanfer I, Augustin T, Raml R, Raney SG, Sinner F. A comprehensive approach to qualify and validate the essential parameters of an in vitro release test (IVRT) method for acyclovir cream, 5%. Int J Pharm. 2018;535:217–27.

    CAS  Article  PubMed  Google Scholar 

  36. 36.

    Kassambara A. and MF. CRAN - Package factoextra [Internet]. 2017 [cited 2020 Jan 5]. Available from: https://cran.r-project.org/web/packages/factoextra/index.html

  37. 37.

    Lê S, Josse J, Husson F. FactoMineR: an R package for multivariate analysis. J Stat Softw [Internet]. 2008;25:4–18 Available from: http://www.agrocampus-rennes.fr/math/le/.

    Google Scholar 

  38. 38.

    ICH. ICH Topic Q2 (R1) Validation of Analytical Procedures : Text and Methodology. Int Conf Harmon. 2005;1994:17.

  39. 39.

    CDER. Validation of Chromatographic Methods [Internet]. 1994. Available from: https://www.fda.gov/downloads/drugs/guidances/ucm134409.pdf

  40. 40.

    EMA. Guideline on the investigation of bioequivalence [Internet]. Eur. Med. Agency ( …. 2010. p. 1–27. Available from: http://scholar.google.com/scholar?hl=en&btnG=Search&q=intitle:GUIDELINE+ON+THE+INVESTIGATION+OF+BIOEQUIVALENCE#0

  41. 41.

    Trottet L, Owen H, Holme P, Heylings J, Collin IP, Breen AP, et al. Are all aciclovir cream formulations bioequivalent? Int J Pharm. 2005;304:63–71.

    CAS  Article  PubMed  Google Scholar 

  42. 42.

    Inoue Y, Furuya K, Matumoto M, Murata I, Kimura M, Kanamoto I. A Comparison of the physicochemical properties and a sensory test of Acyclovir creams. Int J Pharm [Internet]. 2012 [cited 2019 Apr 24];436:265–71. Available from: https://doi.org/10.1016/j.ijpharm.2012.06.023

  43. 43.

    Binder L, Mazál J, Petz R, Klang V, Valenta C. The role of viscosity on skin penetration from cellulose ether-based hydrogels. Skin Res Technol. 2019:1–10.

  44. 44.

    Marto J, Baltazar D, Duarte A, Fernandes A, Gouveia L, Militão M, et al. Topical gels of etofenamate: in vitro and in vivo evaluation. Pharm Dev Technol [Internet]. 2015 [cited 2019 4];20:710–5. Available from: https://doi.org/10.3109/10837450.2014.915571

  45. 45.

    Al-Ghabeish M, Xu X, Krishnaiah YSR, Rahman Z, Yang Y, Khan MA. Influence of drug loading and type of ointment base on the in vitro performance of acyclovir ophthalmic ointment. Int J pharm [internet]. Elsevier B.V.; 2015;495:783–91. Available from: https://doi.org/10.1016/j.ijpharm.2015.08.096, 2015.

  46. 46.

    Bao Q, Shen J, Jog R, Zhang C, Newman B, Wang Y, et al. In vitro release testing method development for ophthalmic ointments. Int J pharm [internet]. Elsevier B.V.; 2017;526:145–56. Available from: https://doi.org/10.1016/j.ijpharm.2017.04.075, 2017.

  47. 47.

    Goebel K, Sato MEO, de Souza DF, Murakami FS, Andreazza IF. In vitro release of diclofenac diethylamine from gels: evaluation of generic semisolid drug products in Brazil. Brazilian J Pharm Sci. 2013;49:211–9.

    CAS  Article  Google Scholar 

  48. 48.

    Khanolkar A, Thorat V, Raut P, Samanta G. Application of quality by design: development to manufacturing of Diclofenac sodium Topical gel. AAPS PharmSciTech [internet]. AAPS PharmSciTech. 2017;18:2754–63. Available from:. https://doi.org/10.1208/s12249-017-0755-8.

    CAS  Article  PubMed  Google Scholar 

  49. 49.

    Lauterbach A, Müller-Goymann CC. Comparison of rheological properties, follicular penetration, drug release, and permeation behavior of a novel topical drug delivery system and a conventional cream. Eur J pharm biopharm [internet]. Elsevier B.V.; 2014;88:614–24. Available from: https://doi.org/10.1016/j.ejpb.2014.10.001, 2014.

  50. 50.

    Kriwet K, Müller-Goymann CC. Diclofenac release from phospholipid drug systems and permeation through excised human stratum corneum. Int J Pharm. 1995;125:231–42.

    CAS  Article  Google Scholar 

  51. 51.

    Nallagundla S, Patnala S, Kanfer I. Comparison of in vitro release rates of acyclovir from cream formulations using vertical diffusion cells. AAPS PharmSciTech [internet]. 2014;15:994–9. Available from: http://www.ncbi.nlm.nih.gov/pubmed/24824173.

  52. 52.

    Petró É, Paál T, Eros I. Drug release from semisolid dosage forms: a comparison of two testing methods. Pharm Dev Technol [Internet]. 2013;7450:1–7. Available from. https://doi.org/10.3109/10837450.2013.867446.

    CAS  Article  Google Scholar 

  53. 53.

    Xu X, Al-Ghabeish M, Krishnaiah YSR, Rahman Z, Khan MA. Kinetics of drug release from ointments: role of transient-boundary layer. Int J pharm [internet]. Elsevier B.V. 2015;494:31–9. Available from. https://doi.org/10.1016/j.ijpharm.2015.07.077.

    CAS  Article  Google Scholar 

  54. 54.

    Xu X, Al-Ghabeish M, Rahman Z, Krishnaiah YSR, Yerlikaya F, Yang Y, et al. Formulation and process factors influencing product quality and in vitro performance of ophthalmic ointments. Int J pharm [internet]. Elsevier B.V. 2015;1:412–25. Available from. https://doi.org/10.1016/j.ijpharm.2015.07.066.

    CAS  Article  Google Scholar 

  55. 55.

    U.S. FDA. Draft guidance on acyclovir. 2016

  56. 56.

    Rowe RC, Sheskey PJ, Owen SC. Handbook of Pharmaceutical Excipients 2012;44:918.

  57. 57.

    Simões A, Veiga F, Vitorino C. Developing cream formulations: renewed interest in an old problem. J Pharm Sci. 2019:1–12.

  58. 58.

    Simões A, Veiga F, Vitorino C. Progressing towards the sustainable development of cream formulations. 2020

  59. 59.

    Ethier A, Bansal P, Baxter J, Langley N, Richardson N, Patel AM. The role of excipients in the microstructure of Topical semisolid drug products. In: Langley N, Michniak-Kohn B, Osborne DW, editors. Role Microstruct top drug prod Dev [internet]. Cham: springer international publishing; 2019. p. 155–93. Available from: https://doi.org/10.1007/978-3-030-17355-5_5

  60. 60.

    Mangas-Sanjuán V, Pleguezuelos-Villa M, Merino-Sanjuán M, Hernández MJ, Nácher A, García-Arieta A, Peris D, Hidalgo I, Soler L, Sallan M, Merino V Assessment of the inter-batch variability of microstructure parameters in topical semisolids and impact on the demonstration of equivalence. Pharmaceutics. 2019;11.

  61. 61.

    Rasmus Broa AKS. Principal component analysis tutorial review. Anal Methods. 2014;6:1–16.

    Article  Google Scholar 

  62. 62.

    Cova TFGG, Jarmelo S, Nunes SCC, Formosinho SJ, de Melo JSS, Pais A. Seeing is believing: a graphical reference framework for multi-criteria evaluation. Evaluation. 2017;23:479–94.

    Article  Google Scholar 

  63. 63.

    Silva J, Mendes M, Cova T, Sousa J, Pais A, Vitorino C. Unstructured Formulation Data Analysis for the Optimization of Lipid Nanoparticle Drug Delivery Vehicles. AAPS PharmSciTech [Internet]. AAPS PharmSciTech; 2018;1–12. Available from: https://doi.org/10.1208/s12249-018-1078-0, 19

  64. 64.

    Cova TFGG, Pereira JLGFSC, Pais AACC. Is standard multivariate analysis sufficient in clinical and epidemiological studies? J biomed inform. 2013;

  65. 65.

    Pleguezuelos-villa M, Merino-sanjuán M, Hernández MJ, Nácher A, Peris D, Hidalgo I, et al. Relationship between rheological properties, in vitro release and in vivo equivalency of topical formulations of diclofenac. Int J pharm [internet]. Elsevier; 2019;118755. Available from: https://doi.org/10.1016/j.ijpharm.2019.118755, 2019.

Download references


Margarida Miranda acknowledges the PhD grant PD/BDE/135075/2017 assigned by FCT (Fundação para a Ciência e Tecnologia, Portugal) and Laboratórios Basi from Drugs R&D Doctoral Program. Tânia Cova also acknowledges the Junior Research grant CEECIND/00915/2018 assigned by FCT. The authors also acknowledge the Coimbra Chemistry Centre, supported by FCT, through the Project UID/QUI/00313/2020.

Author information



Corresponding author

Correspondence to Carla Vitorino.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material


(DOCX 97 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Miranda, M., Cova, T., Augusto, C. et al. Diving into Batch-to-Batch Variability of Topical Products-a Regulatory Bottleneck. Pharm Res 37, 218 (2020). https://doi.org/10.1007/s11095-020-02911-y

Download citation


  • batch variability
  • EMA
  • IVRT
  • Rheology
  • topical products