Dermal toxicology studies are frequently initiated in growing animal models. The test compound is generally applied on a dermal application area (DAA) that is frequently set at certain ratio to total surface area. Since the growth during juvenile period can be significant, the DAA is likely to be impacted during the course of a chronic study. The purpose of this study was 1) to determine if the ratio of the DAA to total body surface area (TBSA) will change proportionally over time with the growth of the miniature swine, and 2) to compare three TBSA formulas. The ratio DAA (cm2surface area) to TBSA was calculated from body weight at periodic intervals for 18 weeks in 16 male and 16 female Hanford miniature swine (~ 4 mo old Hanford miniature swine, averaging ~14 kg at initiation). Two midback5 cm X 5 cm (25 cm2) DAAs, one located on each side of the spine, were used on each subject. The TBSA (m2) was calculated by the well recognized Spectorformula (9.5 x BW(G)2/3/10000,) as well as the Brodieand Wachtelformulas. Using the Spectorformula, the mean ratio DAA to TBSA for week 0 and 8 (N = 32) for an application area was 0.46% ±0.04 and 0.51% ±0.06 (MEAN ±SD), respectively. After week 8, subsequent periodic measurements of the ratio of TBSA to DAA remained steady suggesting proportional changes in growth of both DAA and TBSA. The corrrelationof the three TBSA formulas was >0.99. Thus, comparable TBSA and DAA/TBSA ratio between the three formulas suggested the well recognized SpectorMethod is a valid choice.
Madsen, T., Liu, J., Brown, L., Bouchard, G.F.