Renal CL estimations

From:Batul Parta batulparta@yahoo.com Subject: [NMusers] Renal CL estimations Date: Tue, June 15, 2004 7:44 pm Hi! I think what I am going to ask has been discussed before. Unfortunately, I cannot find it anywhere so I ask it here. I am trying to model the PK of a compound with a fe-value (fraction excreted unchanged in urine) close to 60%. This value is based on total amount found in urine within 24 hours after drug administration (thalf = 3 hrs). All urine was collected and pooled. I was thinking to estimate the renal CL (CLR) by adding an output compartment: DADT(1)=-A(1)*CL/V1 DADT(2)=A(1)*FE*CL/V1 or: DADT(1)=-A(1)*(CLR+CLNR)/V1 DADT(2)=A(1)*CLR/V1 However, this obviously won't work since the amount measured in urine is the sum of all that came out in 24 hours. There is no information over time for the model to be able to pick up the excretion rate. Now, imagine if the urine samples were not pooled and one could get the individual amounts for each urine sample over time. Would that enable me to use the equations above to get an estimation of fe? If so, what is the time-point of the urine measurement? Half-way from the start to the end of the urine collection period, as is done for NCA? I would be very greatful for any published reference. Best regards, B. Parta