Application of quasi-emulsification and modified double emulsification techniques for formulation of tacrolimus microsponges Muhammad Zaman,1 Sundus Qureshi,1 Kishwar Sultana,1 Muhammad Hanif,2 Asif Mahmood,1 Zaib Ali Shaheryar,1 Faisal Gulzar,1 Kashif Barkat,1 Mohamed M Abdel-Daim3 1Faculty of Pharmacy, University of Lahore, Lahore, Pakistan; 2Department of Pharmacy, Bahauddin Zakariya University, Multan, Pakistan; 3Department of Pharmacology, Suez Canal University, Ismailia, Egypt Background: The present study was to develop a stable and sustained-release delivery system of tacrolimus (TCM). TCM is a macrolide antibiotic used as an immunosuppressant. It is formulated as a microsponge, which is a safe and effective delivery system with reduced side effects.Materials and methods: The method used to prepare ethyl cellulose (EC) and xanthan gum (XG)-facilitated EC-based microsponges employed emulsification and modified double emulsification techniques. TCM-containing microsponges were prepared using varying concentrations followed by evaluation of micromeritics, compatibility of drug and excipients, production yield, drug content and entrapment efficiency, zeta potential, size distribution and drug release.Results: The results showed excellent flow properties with adequate entrapment efficiency of the system and satisfactory release of active pharmaceutical ingredient. In vitro dissolution studies, which were conducted to determine the amount of drug released, illustrated a pronounced sustained effect up to 8 h. Zeta size and zeta potential analysis of microsponges confirmed the existence of micro-sized (1.99–3.09 µm) and stable particles (-15.33 to -3.38 mV), respectively.Conclusion: Conclusively, the applied technique and selected combination of ingredients were found suitable for the preparation of TCM-containing sustained-release microsponges. Keywords: ethylcellulose, xanthan gum, macrolides, tacrolimus, sustained release