Lognormal survival in NONMEM?

Dear all, Playing with repeated time to event models, I run into the issue that simple diagnostics for a single time to event outcome suggest that constant hazard and Weibull models are not very appropriate. The lognormal model seems to provide a very nice fit; compared to a constant hazard, the hazard is suggested to be higher in the beginning and then significantly lower at later times. I have not seen any implementations online: does anyone know if the lognormal survival function can be implemented in NONMEM, and/or can anyone suggest alternative approaches? Some time-varying function to modify the hazard? Any and all suggestions appreciated! Kind regards, Rik Rik Schoemaker, PhD Occams Coöperatie U.A. Malandolaan 10 1187 HE Amstelveen The Netherlands http://www.occams.com +31 20 441 6410 [email protected]<mailto:[email protected]> [cid:[email protected]]