Interspecies Scaling Allometric Proportion to body weight varies exponentially across species Y = aWb Y = Pharmacokinetic parameter; W = Body weight a = Allometric coefficient; b = scaling exponent

b ~ 0.25

• Heart rate

• Circulation time

• Respiratory rate

b ~ 0.75

• Basal metabolic rate

• Blood flow

• Clearance (flow limited?)

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