APATITE AS CARRIER FOR GROWTH-HORMONE - IN-VITRO CHARACTERIZATION OF LOADING AND RELEASE

Previous studies concerning bone drug delivery systems have provided l ittle data about the amount of drug loaded, one of the essential facto rs for determining the dose/effect relationship. To investigate this f actor, an adsorption method involving a therapeutic agent was tested i n vitro on an apatitic calcium phosphate (AP). One milligram of human growth hormone (hGH) was deposited onto 0.1, 0.15, and 0.2 g of AP pow der over a period of 24 h at 37 degrees C. The amount of hGH loaded wa s determined by subtracting the dose recovered from that applied on AP . The results show that 1 g of AP adsorbed 9.48 mg of hGH. From 0.1 an d 0.15 g of hGH-loaded AP, hGH was released in vitro for 2 and 3 weeks , respectively, with a 50% time release (T1/2) at 30 h and 72 h, respe ctively, for the two quantities. The amount of drug loaded and the det ermined release kinetics were compatible with the action pattern of hG H, indicating that hGH-loaded calcium phosphate supports are suitable for bone-growth promotion. (C) 1997 John Wiley & Sons, Inc.