*3.4.4 Racemization*

It is an event where optically active molecule becomes inactive without any change in molecular composition. Such study is of highest importance when racemic mixture

**11**

*Preformulation Studies: An Integral Part of Formulation Design*

form is used. Racemization leads to either loss of pharmacological action or toxic effect may be enhanced by severalfold. Racemization is mostly affected by the conditions like pH, type of solvents, presence of light, and temperature. So main goal in this study is to design optimum condition in which molecule can remain stable [10].

Most often than not, new chemical entity exists in solid form and the properties under study during preformulation phase are bulk property characterization and micromeritic property characterization. Bulk property characterization includes study of polymorphism, crystallinity, density, nature of molecule like deliquescence or hygroscopicity and micromeritic characterization includes study of particle size, shape, porosity, and density. As most of the new chemical entities are solids, they exist either as amorphous or in crystalline state. Either of the form imparts the two

One of the most widely studied techniques during preformulation analysis is solubility profile of drug candidate. It is the backbone study of preformulation stage that determines the performance of developed formulation. Solubility and permeability forms the scientific basis of biopharmaceutics classification system (BCS), which can provide framework for designing type of drug delivery system. **Table 2** provides basic idea about basic BCS classification and link between solubility,

The solubility of a drug is the amount of the drug that dissolves in a given solvent to produce a saturated solution at constant temperature and pressure. **Table 3** provides outline of different levels of solubility. For conversion of drug molecule into an effective oral formulation, it must have good aqueous solubility for better absorption. Solubility is not an independent parameter but it relies on several properties like crystal characteristics, temperature, pH, complexation, and molecular structure. There are several techniques, which are available to improve the solubility

Amorphous drugs have randomly arranged molecules or atoms in the molecular lattice. Typical amorphous forms are obtained by techniques like precipitation, rapid cooling after melting, and lyophilization. One of the most important advantages associated with amorphous form is the higher solubility and hence the higher dissolution rate. More often than not drugs with low water solubility lead to poor bioavailability and variable clinical response. So, polymorphic form may overcome this problem

*DOI: http://dx.doi.org/10.5772/intechopen.82868*

**4. Physical characterization of molecule**

main virtues that are stability and solubility.

permeability, and type of targeted formulation.

of drug candidate, which are as follows:

• Chemical modification of drug

• Particle size reduction

**4.2 Crystalline vs amorphous form**

• Hydrotropy

• Complexation

• Addition of cosolvent or surfactant

**4.1 Solubility**

form is used. Racemization leads to either loss of pharmacological action or toxic effect may be enhanced by severalfold. Racemization is mostly affected by the conditions like pH, type of solvents, presence of light, and temperature. So main goal in this study is to design optimum condition in which molecule can remain stable [10].
