Patent ID: 8741263

Claim:
A method for determining the metabolic rate of a test molecule in an animal, the method comprising the steps of: a) administering a first molecule and a second molecule to the animal, wherein the second molecule is cleared from the animal at a rate lower than the rate at which the first molecule is cleared from the animal; b) determining the molecular ratio (R B /R A ) of the first molecule to the second molecule in the animal over a period of time to obtain a time series of molecular ratios (R B /R A ) (t) , the molecular ratio (R B /R A ) being determined using the following equation: R B /R A =I B /I A , wherein I B is the level of the first molecule in the animal and I A is the level of the second molecule in the animal; c) determining the rate constant of kidney clearance of the first molecule (k i ) from the time series of molecular ratios (R B /R A ) (t) using the equation: ( R B /R A ) (t) =c+a *exp(− kt ), wherein c is a constant, a is a pre-exponential factor, and t is time; d) administering the test molecule for determination of the metabolic rate and the second molecule to the animal and determining the molecular ratio of the test molecule to the second molecule (R C/A ) over a period of time to obtain a time series of molecular ratios of the test molecule to the second molecule ((R C/A ) (t) ); and e) performing a least square fitting of the time series of molecular ratios of the test molecule to the second molecule ((R C/A ) (t) ) to obtain the metabolic rate of the test molecule (M (km,t) ) according to the equation: ( R C/A ) (t) =c+a * exp(−k 1 t)+ M (km,t) wherein c is a constant, k 1 is the rate constant of clearance of the first molecule, a is a pre-exponential factor, and t is time.