# PharmPK Discussion - Amount of Drug in Peripheral Compartment (3C Model)

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• On 20 Jan 2003 at 10:15:46, "Gregg Timony" (gtimony.-a-.conformacorp.com) sent the message
`The following message was posted to: PharmPKHello All,         To calculate the amount of drug in a peripheral compartment vstime for a 2 compartment open model         (IV bolus to central with elimination only from central) I'veused:           mass in peripheral compartment =  K12*Dose(alpha-beta) x(e-beta x t - e-alpha x t)         I'm working with a compound that shows distinct 3 compartmentbehavior following IV bolus dosing and         I haven't been able to work out the analogous equations forcompartments 2 and 3.         Assuming central compartment dosing, elimination only from thecentral compartment, with compartment         1 centrally positioned with connectivity to compartments 2 and3 (k12/k21, K13/k31)........         can someone provide equations for the mass in compartments 2and 3 over time?            Appreciate Your Assistance,            GreggGregg A. Timony, M.S.Head, Toxicology and ADMEPreclinical DevelopmentConforma Therapeutics9393 Towne Centre Drive, Suite 240San Diego, CA  92121(858) 795-0124[Do you meanmass in peripheral compartment =  (K12*Dose/(alpha-beta)) x (e-beta x t- e-alpha x t)for the two compartment model.The Laplace of the amount in compartment 3 is:L(X3) = k13*(s+k21)*Dose/((s+alpha)*(s+beta)*(s+gamma))The fingerprint method will help with the back-transformhttp://www.boomer.org/c/p3/c07/c0702.html- db]`
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