Sebhatu T, Elamin A A, Ahlneck C
Department of Pharmacy, Uppsala University, Sweden.
Pharm Res. 1994 Sep;11(9):1233-8. doi: 10.1023/a:1018973923831.
Spray dried (15% amorphous) lactose absorbs moisture when exposed to humidity. At 57% relative humidity (RH), the moisture uptake was 1.5%. It is suggested that the moisture is preferentially taken up in the amorphous regions, thereby increasing the actual moisture content in the amorphous parts up to 10%. The moisture uptake reduced the glass transition temperature below the operating temperature and thereby transformed the amorphous regions from a glassy to a rubbery state, setting up conditions for crystallisation of the lactose. Compaction of dry spray dried lactose led to a relatively low initial tablet strength. However, when pre-exposed to 57% RH for a short time period (2 to 4 hours) before compaction, the initial tablet strength increased markedly. This was due to moisture uptake which resulted in a higher molecular mobility of the amorphous spray dried lactose, and to an increase in plastic flow. Post compaction storage of tablets containing amorphous regions of spray dried lactose at 57% RH resulted in an increased tablet strength after 4 hours due to crystallisation. Spray dried lactose exposed to 57% RH for more than 6 hours before compaction led to the lowest initial tablet strength. Crystallisation of the amorphous regions of the spray dried lactose occurred before tabletting. No increase in tablet strength was noted on post compaction storage for these tablets.
喷雾干燥（15%为非晶态）的乳糖在暴露于湿度环境时会吸收水分。在57%相对湿度（RH）下，吸湿率为1.5%。据推测，水分优先在非晶态区域被吸收，从而使非晶态部分的实际水分含量增加至10%。吸湿降低了玻璃化转变温度至操作温度以下，从而将非晶态区域从玻璃态转变为橡胶态，为乳糖的结晶创造了条件。干燥的喷雾干燥乳糖压片导致初始片剂强度相对较低。然而，在压片前短时间（2至4小时）预暴露于57% RH时，初始片剂强度显著增加。这是由于吸湿导致喷雾干燥的非晶态乳糖分子流动性更高，以及塑性流动增加。含有喷雾干燥乳糖非晶态区域的片剂在57% RH下压片后储存4小时，由于结晶导致片剂强度增加。在压片前将喷雾干燥乳糖暴露于57% RH超过6小时会导致最低的初始片剂强度。喷雾干燥乳糖的非晶态区域在压片前就发生了结晶。对于这些片剂，压片后储存时未观察到片剂强度增加。
