Chandra,
Pediatric data alone may not be able to support (with 3 samples per
patient) a two compartment model. So combined adult/pediatric model is
more appropriate. You may also want to scale peripheral compartment
parameters (Q as CL, V2 as V, K12and K21 as CL/V ~ 1/WT^0.25). Remaining
dependence of CL on WT (if any is noticeable) for very young kids could
be attributed to maturation and explained by AGE covariate
Leonid
--------------------------------------
Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
web: www.quantpharm.com
e-mail: LGibiansky at quantpharm.com
tel: (301) 767 5566
Chandrasekhar Udata wrote:
Hi,
I am working on a pop PK model to estimate PK parameters in pediatric
and adult patients. Pediatric study (n=20, age <6 yrs) has fewer samples
(3) per subject whereas the adult study (n=50, median age 20 yrs) has 12
samples per subject. A two-compartment model best describes the data for
each data set. Although a two-compartment model best describes the
combined data, the individual parameter estimates in pediatric
population are different compared to those obtained using with pediatric
data alone. Note that the parameter estimates in adults were not
significantly altered with either combined or adult data alone. Body
weight is the only covariate included in the model with allometric
exponents fixed to 0.75 on CL and 1 on V1.
I would like to hear your thoughts on this and any suggestions on how to
proceed with modeling combined data from pediatric and adult studies.
Regards,
- Chandra
