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**25** 

*India* 

**Preparation of Carvedilol Spherical Crystals** 

Solid dispersion is one of the most efficient techniques to improve the dissolution rate of poorly water-soluble drugs, leading to an improvement in the relative bioavailability of their formulations. At present, the solvent method and the melting method are widely used in the preparation of solid dispersions. In general, subsequent grinding, sieving, mixing and

The spherical agglomeration technique has been used as an efficient particle preparation technique developed by Kawashima in the 1980s (Kawashima et al., 1994). Initially, spherical agglomeration technique was used to improve powder flowability, packability, and compressibility (Usha et al. 2008; Yadav and Yadav, 2008; Bodmeier and Paeratakul et al., 1989). Then polymers were introduced in this system to modify their release (Di Martino et al., 1999). Currently, this technique is used more frequently for the solid dispersion preparation of water-insoluble drugs in order to improve their solubility, dissolution rate and simplify the manufacturing process (Cui et al.*,* 2003, Tapas et al. 2009, 2010). Spherical crystallization has been developed by Yoshiaki Kawashima and co-workers as a novel particulate design technique to improve processibility such as mixing, filling, tableting characteristics and dissolution rate of pharmaceuticals (Kawashima et al., 1974, 1976, 1981, 1982, 1983, 1984, 1985, 1989, 1991, 1994, 1995, 2002, 2003). The resultant crystals can be designated as spherical agglomerates (Kulkarni and Nagavi, 2002). Spherical crystallization is an effective alternative to improve dissolution rate of drugs (Sano et al., 1992). Now days functional drug devices such as microspheres, microcapsules, microballoons and biodegradable nanospheres were developed using the emulsion solvent diffusion techniques involving the introduction of a functional polymer into the system (Di Martino et al., 1999; Marshall and York, 1991; Garekani and Ford, 1999). This can be achieved by

granulation are necessary to produce the different desired formulations.

**1. Introduction** 

various methods such as

4. Neutralization (NT)

1. Spehrical Agglomeration (SA)

2. Quasi Emulsion Solvent Diffusion (QESD) 3. Ammonia Diffusion System (ADS)

**Having Solid Dispersion Structure by the** 

**Emulsion Solvent Diffusion Method and Evaluation of Its** *in vitro* **Characteristics** 

Amit R. Tapas, Pravin S. Kawtikwar and Dinesh M. Sakarkar *Sudhakarrao Naik Institute of Pharmacy, Pusad, Dist Yavatmal, Maharashtra* 

