Re: ka and Duration

From: "Gastonguay, Marc" marcg@metrumrg.com Subject: Re: [NMusers] ka and Duration Date: Sat, 07 Jan 2006 16:49:58 -0500 Dear Mahesh, You can limit the duration of a first order input by turning off the depot compartment at the time the first-order process ends. This method requires the use of PREDPP and is done through the NMTRAN data set. For example, if you have a 100 mg transdermal patch administration for 7 days, the patch is compartment 1 and the central compartment is 2: ID TIME CMT AMT EVID DV 1 0 1 100 1 . ; insert concentration observation records - for example 1 2 2 . 0 23 . . . 1 7 -1 . 2 . 1 7 1 . 2 . ; insert concentration observations and additional dosing records as needed ...where TIME is in days and AMT is in mg The negative CMT number at TIME=7 signifies a reset to zero for that compartment only, and is implemented on an "OTHER" data record (EVID=2). I've turned the compartment on again at the same time by the following record with TIME=7 and CMT=1, in case you want to add additional doses at later times. You will need to turn off the depot compartment anytime you want to limit the duration of the first-order input. No changes are necessary in the control stream; estimate KA as you normally would. Be aware that when you use this method, your model could result in less than complete absorption of the total amount of drug administered (e.g. drug remaining in the patch after removal). Hope this helps. Marc Marc R. Gastonguay, Ph.D. marcg@metrumrg.com