Physical characterization of dibasic calcium phosphate dihydrate and anhydrate.
The dehydration of different commercial brands of dibasic calcium phosphate dihydrate (DCPD; CaHPO(4).2H(2)O) was examined over a range of temperatures and water vapor pressures. To determine the main factors affecting the physical stability of DCPD, the baseline characterization of DCPD and dibasic calcium phosphate anhydrate (DCPA; CaHPO(4)) was conducted by thermogravimetric analysis, differential scanning calorimetry and X-ray diffractometry. The surface area and the DCPA content (present as an impurity) depended on the commercial source of DCPD. The larger particles contained a higher concentration of DCPA and the anhydrate exhibited a concentration-dependent acceleratory effect on the dehydration of DCPD. Unlike DCPD, DCPA is physically stable and resisted hydration even when dispersed in water for over 7 months in the temperature range of 4-50 degrees C. In dosage forms containing DCPD, there is a potential for phase transformation to DCPA, while the reverse transition, that is, DCPA --> DCPD appears to be extremely unlikely. Thus, the risk of physical transformation can be minimized by using DCPA in formulations.
Miyazaki
Tamaki
T
Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455-0505, USA.
Sivaprakasam
Kannan
K
Tantry
Jaidev
J
Suryanarayanan
Raj
R
D002130:Calcium Phosphates / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D003681:Dehydration; D010316:Particle Size; D013696:Temperature; D013818:Thermogravimetry; D055548:Vapor Pressure; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
D002130:Calcium Phosphates; D014867:Water; C485829:calcium phosphate, dibasic, anhydrous; C494366:calcium phosphate, dibasic, dihydrate