Calcium Phosphate in Pharmaceutical Product Development

Abstract

Calcium phosphate is a widely used pharmaceutical excipient as binder and filler in solid oral dosage forms which include compressed tablets and hard gelatin capsules. A review of the marketed tablets and capsules indicated that several of them contain calcium phosphate. Some of the commonly used dosage forms are Benadryl®, Sudafed®, Decadron®, Norvasc®, Ex-Lax®, and Gas-X®. The wide acceptance of calcium phosphate is primarily due to its excellent flowability and compressibility characteristics. The relatively low cost and its elemental calcium value adds to its popularity. It is mainly used as anhydrous and dihydrate forms of dibasic calcium phosphate, and tribasic calcium phosphate. While the calcium phosphate dihydrate is commercially available from different sources, Emcompress® from Mendell and Di-Tab® from Stauffer are very popular. The present chapter focuses on the physical and chemical properties of these calcium phosphates, flow property measurements, compressional behavior and the forces involved, tablet compression studies, and certain excipient incompatibilities. Calcium phosphates have also been used as anti-caking or flocculating agents in suspensions, and adsorbent or thickening agents in ointments and creams. However, the present chapter is focused towards its use in solid dosage forms. Since the present book is intended for a multidisciplinary readership, an introduction is provided for the method of preparation of tablets, type of tablets, function of tablet excipients, and the evaluation of compressed tablets.