# Two absorption compartment and ADDL **URL:** \ **Category:** Modelling and Simulation\ **Created:** [February 28, 2023, 4:32pm UTC](https://forum.certara.com/t/two-absorption-compartment-and-addl/3665 "2023-02-28T16:32:22Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![vetpharma](https://avatars.discourse-cdn.com/v4/letter/v/a183cd/32.png) [@vetpharma](https://forum.certara.com/u/vetpharma)\ **Post date:** [February 28, 2023, 4:32pm UTC](https://forum.certara.com/t/two-absorption-compartment-and-addl/3665/1 "2023-02-28T16:32:22Z")
Hi, I am modeling a compound that has mix of IR and SR formulations. The data are from a clinical trial with three times administration a day and sampling at day 18. I defined two absorption compartment with Tlag on the second one. The problem is when I use ADDL the Ka2 appears after Ka1 (cycle time 48 h). however, when I use actual time of administration (as single dose) Ka1 and Ka2 are at their correct time. I would appreciate it if you help me with this issue. How can I use delta time to count for cycle time of 24 hours without giving Ka2 after Ka1. I would like to have them at the right time of administration. (model is attached) Kind regards Amir ---
**Author:** ![cradhakr](https://avatars.discourse-cdn.com/v4/letter/c/7feea3/32.png) [@cradhakr](https://forum.certara.com/u/cradhakr)\ **Post date:** [February 28, 2023, 10:02pm UTC](https://forum.certara.com/t/two-absorption-compartment-and-addl/3665/2 "2023-02-28T22:02:06Z")
Hi Amir, Thanks for reaching out. We did not receive the project file - could you please attach it again or you could e-mail to [support@certara.com](mailto:support@certara.com). Thanks Mouli ---
**Author:** ![vetpharma](https://avatars.discourse-cdn.com/v4/letter/v/a183cd/32.png) [@vetpharma](https://forum.certara.com/u/vetpharma)\ **Post date:** [February 28, 2023, 10:42pm UTC](https://forum.certara.com/t/two-absorption-compartment-and-addl/3665/3 "2023-02-28T22:42:49Z")
> [@cradhakr](#): > > Hi Amir, > > Thanks for reaching out. We did not receive the project file - could you please attach it again or you could e-mail to [support@certara.com](mailto:support@certara.com). > > Thanks > > Mouli Hi Mouli, Sorry I forgot to press attach at the end. Now, I think you get it. Best Amir [ADDL or Not.phxproj](https://forum.certara.com/uploads/short-url/2IWk8s9P9UXalWf5yyKS9P0SfPK.phxproj) (231 KB) ---
**Author:** ![cradhakr](https://avatars.discourse-cdn.com/v4/letter/c/7feea3/32.png) [@cradhakr](https://forum.certara.com/u/cradhakr)\ **Post date:** [March 1, 2023, 10:49am UTC](https://forum.certara.com/t/two-absorption-compartment-and-addl/3665/4 "2023-03-01T10:49:25Z")
Hi Amir, I have attached the project file for you. I have split the data and did the analysis for one subject. For each formulation I created a row (see NBI\_OPC\_1722\_10011001 from Split). Please have a look and let me know if this is what you are looking for. If you need some further clarification please reachout to us on [support@certara.com](mailto:support@certara.com) and I shall organise for a quick teams session. Thanks Mouli [2023 Mar\_Forum\_ADDL or Not.phxproj](https://forum.certara.com/uploads/short-url/pFSfJfGoBoXb74o8NDLT92DzJ1Z.phxproj) (1.96 MB) ---
**Author:** ![Samer\_Mouksassi](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@Samer\_Mouksassi](https://forum.certara.com/u/Samer_Mouksassi)\ **Post date:** [March 1, 2023, 12:00pm UTC](https://forum.certara.com/t/two-absorption-compartment-and-addl/3665/5 "2023-03-01T12:00:54Z")
adding link to the ADDL documentation [https://onlinehelp.certara.com/phoenix/8.3/index.html#t=topics%2FMore\_on\_ADDL.htm&rhsearch=ADDL&rhhlterm=ADDL&rhsyns=%20](https://onlinehelp.certara.com/phoenix/8.3/index.html#t=topics%2FMore_on_ADDL.htm&rhsearch=ADDL&rhhlterm=ADDL&rhsyns=%20) please have a special look at Specifying steady state and additional doses outside of the user interface sscol(SS) iicol(II) ssoffcol(SSOffset)