Some drugs are too unstable either physically or chemically in an aqueous medium to allow formulation as a solution, suspension, or emulsion. Therefore to overcome the stability problem, the drug is formulated as a dry powder that is reconstituted by addition of water before administration. The technique is known as lyophilization. Lyophilization is a technique based on process called sublimation. The problem like decreased shelf life, dissolution drawback and difficulty in storage are also overcome by using lyophilization technique. Differential scanning calorimetry method helps to set the lyophilization cycle.