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. Author manuscript; available in PMC: 2017 Feb 1.
Published in final edited form as: J Clin Pharmacol. 2016 Aug 23;57(2):219–229. doi: 10.1002/jcph.796

Figure 1. Diagram of the one-compartment open model with two parallel sites of absorption used in the pharmacokinetic analysis of metformin.

Figure 1

X1, amount of metformin in the central compartment; D, dose; F, drug bioavailability; f, fraction of metformin absorbed at the first absorption site; ka1, absorption rate constant at the first absorption site; ka2, absorption rate constant at the second absorption site; tx, time for the second fraction of the drug to begin to be absorbed; V, volume of distribution of the central compartment; CL, clearance of metformin from the central compartment