The use of LC/MS, GC/MS, and LC/NMR hyphenated techniques to identify a drug degradation product in pharmaceutical development.

Understanding drug degradation in the formulated product is critical in pharmaceutical development as it has significant impacts on drug efficacy, safety profile and storage conditions. As a result, identification of degradation compounds has taken an important role in the drug development process. In this study, various hyphenated analytical techniques, such as liquid chromatography mass spectrometry (LC/MS), gas chromatography mass spectrometry (GC/MS), and liquid chromatography nuclear magnetic resonance with a solid phase extraction interface (LC/SPE/NMR), have been applied to the identification of a drug degradation product which grew over time in the stability study of the drug product. The target unknown is less polar and more unsaturated than the drug substance based upon reverse phase HPLC relative retention time and UV spectra. It is not ionizable by electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) in either a positive or a negative mode. The unknown was isolated by an HPLC fraction collector and enriched by solid phase extraction. GC/MS with chemical ionization (CI) was employed to determine the molecular weight of this compound. Its fragmentation pattern was determined by CI-MS/MS using an ion trap mass spectrometer. The isolated material was also analyzed by LC/SPE/NMR, from which the structure of this compound was further characterized. The study utilizes a combination of various hyphenated analytical techniques to obtain complimentary information for structure elucidation of the unknown. The combination approach is critical for unambiguous impurity structure elucidation in drug degradation studies of pharmaceutical drug products.

Waist-to-hip ratio and adipose tissue distribution: contribution of subcutaneous adiposity.

The waist-to-hip ratio (WHR) reflects the relative distribution of adipose tissue in the human body. However, whether this is due to the musculoskeletal structures of the waist and hip or the overlying subcutaneous adipose tissue has been disputed. We measured waist and hip girths in 11 male and 11 female cadavers, aged 55-94 years, before and after complete removal of skin and subcutaneous adipose tissue. Girths measured following removal of subcutaneous adipose tissue were termed "waist gx" and "hip gx", and their ratio "WHRx". Masses of regional adipose tissue segments were obtained by complete dissection, and the adipose mass ratios "trunk/arm-plus-leg", "trunk/leg", "internal/arm-plus-leg", and "internal/leg" were derived. As assessed by analysis of variance, WHR accounted for significant (P < 0.05) portions of the variance in all adipose mass ratios; adjustment for internal adipose mass increased the significance of all these relationships (P < 0.005). The ratio WHRx was not related to any ratio of regional adipose masses. Waist girth was related to trunk (P < 0.001) and internal (P < 0.05) adipose masses, and hip girth was related to arm-plus-leg adipose mass (P < 0.0001) and leg adipose mass (P < 0.0001), but waist gx and hip gx were not related to dependent variables. The results indicate that the ability of WHR and waist and hip girths to reflect the regional distribution of adipose tissue in the body is dependent upon the subcutaneous adipose tissue mass of the waist hip area, not its musculoskeletal constituency.

Human body composition: A review of adult dissection data.

Although body composition analysis is popular, dissection data are sparse and sometimes difficult to access. Published data that include the weights of skin, adipose tissue, muscle, and bone, along with body weight, are reviewed. The 31 men and 20 women include 34 cadavers from three separate dissection studies in Brussels, 12 from 19th century reports, and 5 from the United States. The age range was 16-94y. Men differed from women in that they had less adipose tissue and more muscle in both absolute and relative terms. The body mass index (BMI) did not differ between the sexes, because lower weights of muscle and bone compensated for the greater adiposity in women. The relationship between the BMI and relative adiposity was significant, but the BMI explained only about one-third of the variance in adiposity, indicating that in this sample it is a poor predictor of fatness. The composition of the fat-free weight (FFW) and adipose tissue free weight (ATFW), though less variable than body weight, showed enough variability that the assumption of constancy of the fat-free body required for densitometry and other indirect methods of fat estimation, could not be supported. In the few dissections that did fat extraction, essential on non-adipose fat, varied from 4-14% of the FFW, thus undermining the concept of lean body weight. More dissection data are needed, especially in children and adolescents, and especially in conjunction with in vivo body composition methods to help in their validation. Am. J. Hum. Biol. 11:167-174, 1999. Copyright 1999 Wiley-Liss, Inc.