Tablets & Capsules

TC0519

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Tablets & Capsules May 2019 39 eye on Daniel Zakowiecki, Marek Lachmann, and Tobias Hess Budenheim excipients This edition of Eye on Excipients describes the benefits of using calcium phosphate excipients in direct-compression (DC) tableting applications and compares sev- eral DC calcium phosphate types. The pharmaceutical industry has been using calcium salts of ortho- phosphor ic acid (calciu m phos- phates) for many years. Calcium phosphates possess many physical and chemical properties that make them ideal candidates for use as excipients in solid oral dosage for- mulations. Until recently, they were conside r ed inac t ive ing r ed ients used only as fillers/diluents to bulk up formulations and facilitate their further processing [1]. Their func- tionality goes far beyond being a mere filler, however, and when used a p p r o p r i a t e l y, t h e y c a n h e l p improve drug product efficacy as well as long-term stability. Calcium phosphates are inorganic substances of mineral origin and are, therefore, characterized by excep- tional chemical stability. For the same reason, they are compatible with most known drug substances. A few exceptions include indomethacin and tetracycline antibiotics, which com- bine with the calcium ions to form poorly soluble complexes. Also, triba- sic calcium phosphate (USP mono- graph) is incompatible with tocoph- eryl acetate due to the large number of hydroxyl groups on the surface of the substance [1, 2]. Because calcium phosphates do not interact with water, they can be successfully used as a completely inert densifier in any process involv- ing water. Due to their very high cal- cium and phosphorus content, they are often used in dietar y supple- ments. Calcium phosphate hydroxy- apatite in particular finds widespread use in supplements because its calci- um-to-phosphorus ratio is identical to that of human bone [3, 4]. The functional properties of cal- cium-phosphate-based excipients Figure 1 SEM images of calcium phosphate excipients d. Tribasic calcium phosphate (Tri-Cafos 500) c. Dibasic calcium phosphate anhydrous (Di-Cafos A60) b. Dibasic calcium phosphate anhydrous (Di-Cafos A150) a. Dibasic calcium phosphate dihydrate (Di-Cafos D160)

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