Re: [NMusers] Variability on infusion duration

2020-08-05 Thread Ayyappa Chaturvedula
Hi Patricia, What is the purpose of your modeling exercise? I am not sure your scenario could be assigned to any particular distribution. If you intend to simulate population from the model, then your assumptions would not be reasonable. If you have rich data, you may try individual modeling ap

Re: [NMusers] Variability on infusion duration

2020-08-05 Thread Ayyappa Chaturvedula
Hi Patricia, What is the purpose of your modeling exercise? I am not sure your scenario could be assigned to any particular distribution. If you intend to simulate population from the model, then your assumptions would not be reasonable. If you have rich data, you may try individual modeling ap

RE: [NMusers] Variability on infusion duration

2020-08-05 Thread Bill Denney
Similar to Leonid's solution, you can try using an exponential distribution: D1 = DUR*(1-EXP(-EXP(ETA(1 The exponential within an exponential gives left skew and ensures that D1 ≤ DUR. For subjects who you know had an incomplete infusion duration, I would add an indicator variable (1 if inco

Re: [NMusers] Variability on infusion duration

2020-08-05 Thread Sam Liao
Just realized the typical value of this estimate cannot be 1.0. You may need other transformation. Sam > On August 5, 2020 9:59 AM Sam Liao wrote: > > > Dear Patricia, > This distribution might to analogous to relative bioavailability estimate, > which is bounded between 0 to 1. Typically,

Re: [NMusers] Variability on infusion duration

2020-08-05 Thread Sam Liao
Dear Patricia, This distribution might to analogous to relative bioavailability estimate, which is bounded between 0 to 1. Typically, we use the logit-transformation in F1 estimate. For example: m1 = log(θ1/(1- θ1)) EE1 = m1 + η1 F1 = exp(EE1)/[1 +exp(EE1)] Best regard

Re: [NMusers] Variability on infusion duration

2020-08-05 Thread Leonid Gibiansky
may be D1=DUR*EXP(ETA(1)) IF(D1.GT.DocumentedInfusionDuration) D1=DocumentedInfusionDuration On 8/5/2020 12:18 PM, Patricia Kleiner wrote: Dear all, I am developing a PK model for a drug administered as a long-term infusion of 48 hours using an elastomeric pump. End of infusion was documented

[NMusers] Variability on infusion duration

2020-08-05 Thread Patricia Kleiner
Dear all, I am developing a PK model for a drug administered as a long-term infusion of 48 hours using an elastomeric pump. End of infusion was documented, but sometimes the elastomeric pump was already empty at this time. Therefore variability of the concentration measurements observed at thi