# PharmPK Discussion - Conversion of lambdas to rates

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• On 9 Jul 2013 at 23:14:45, Batul Parta (batulparta.-at-.yahoo.com) sent the message
`Dear all,I am reading an article where the authors report modeling results of data after iv infusion. A twocompartment model fitted the data and they present lambda1, lambda2, CL, Vdc and Vdss. Could someoneplease provide a reference on how to convert lambda1 and lambda2 to k12 and k21? I want to simulatedifferent doses using this model and am not sure how to use the lambdas for simulations.Thank you in advance,BPBatul Parta `
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• On 10 Jul 2013 at 08:45:26, Mukul Minocha mukul.minocha.-at-.gmail.com sent the message
`Hi Batul,The relationship is as follows:α + β = kel + k12 + k21α * β = kel * k21k12 = (rate constant from Central to Peripheral cmt)k21 = (rate constant from Peripheral to Central cmt)kel = CL/Vcusually, α and β are calculated, given rate constants as:[(α + β)+/- (sqrt(α + β)^2 - 4*α * β)]/2More information could be found with an example athttp://www.boomer.org/c/p4/c19/c19.pdfBestMukul MinochaCTMUniversity of Maryland Baltimoremukul.minocha.-a-.gmail.com[I'm not sure if the alpha and beta symbols will get through on the new system. We'll  give it atry. Also, other links that might be useful is http://www.boomer.org/c/p4/c19/c1902.htmland http://www.boomer.org/c/p4/c19/c1903.html- db]`
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• On 10 Jul 2013 at 08:47:53, Ankur Sharma ankur-sharma.-a-.ouhsc.edu sent the message
`Dear Batul,Kindly see the following article and the reference by Wagner, 1975 cited inthe article to calculate the micro rate constants (K12, K21) from thehybrid or macro rate constants (lambda1, lambda2). This article helped mein calculating the macro rate constants."Calculating the hybrid (macro) rate constants of a three-compartmentmamillary pharmacokinetic model from known micro-rate constants" in, Journalof Pharmacological and Toxicological Methods 49 (2004) 65–68.Hopefully it works for you.All the best !!Thank you and best regards,-AnkurAnkur SharmaGraduate Research Assistant, College of PharmacyUniversity of Oklahoma Health Sciences Center1110 N Stonewall AvenueOklahoma City, OKC, OK 73117Email: ankur-sharma.at.ouhsc.edu`
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