SURFACE-AREA TO VOLUME RELATIONSHIPS OF SNAKES SUPPORT THE USE OF ALLOMETRIC SCALING FOR CALCULATING DOSAGES OF PHARMACEUTICALS

Metabolic scaling is used to estimate pharmaceutical dosages for snake s because few pharmacokinetic studies have determined optimum dosages. The question arose as to the validity of the assumption of metabolic scale among snakes because they have such a cylindrical shape. The sur face area to volume relationships of a group of animals is a major por tion of the metabolic scaling exponent of 0.75. An assumption inherent in scaling pharmaceutical dosages for snakes is that there is not a s hape change with a size change, or that scaling of the surface area to volume has an exponent of 0.66. One hundred forty snakes, 106 Colubri dae and 34 Boiidae, were weighed, their volume was determined by water displacement, and the snakes were measured. Geometric formulas were u sed to calculate surface area and volume of each snake. Surface area t o volume relationship was nearly isometric, with a scaling exponent of 0.64, supporting the use of metabolic scaling for estimating pharmace utical doses.