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Fitting single model to IV and SC data in a crossover study


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#1 BP1968

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Posted 10 December 2020 - 09:51 PM

I am trying to fit a single model to IV and SC data obtained on separate occasions in a few subjects (crossover design) using NLME. I have a model that works, but does not consider the crossover part (i.e. considers that the IV and SC data were obtained in different subjects) and am not sure how to specify the crossover aspect.

 

Thank you,

 

BP



#2 kniefort

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Posted 11 December 2020 - 02:29 AM

Hi BP,

 

See attached example that shows one way to do this using a text model.  Basically you need a dose column for oral, a dose column for IV, and you use 2 dosepoints in the model with a bioavailability term for the oral dose.  Please post if you have any questions.

 

Kind Regards,

 

Keith

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#3 BP1968

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Posted 11 December 2020 - 02:42 AM

Hi BP,

 

See attached example that shows one way to do this using a text model.  Basically you need a dose column for oral, a dose column for IV, and you use 2 dosepoints in the model with a bioavailability term for the oral dose.  Please post if you have any questions.

 

Kind Regards,

 

Keith

Hi Keith,

 

Thank you for your response. In your example, both the oral and IV administration were used in a single episode. In mine, the same subjects were studied on 2 separate occasions, and received the drug IV once and SC on the other occasion. I tried to setup the data as in your example, but it does not work, presumably because I do not specify that the occasions are separate (and there is a single ID per subject - my setup works fine when I give a different ID for the IV and SC treatments).

 

Thank you,

 

BP



#4 kniefort

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Posted 19 December 2020 - 12:18 AM

Hi BP, 

 

You need to just use running time for each individual.  Period 1 (Study Day 1) starts at time 0, and then the start time for e.g., Period 2, Day 8 would be time 168.  This ensures there will be one parameter set per individual for each dose event.  If this is not clear, please post an example of your dataset and we will take a look.  Perhaps I am not understanding what you are trying to do.

 

Best Regards,

 

Keith  



#5 BP1968

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Posted 29 December 2020 - 01:08 AM

Hi BP, 

 

You need to just use running time for each individual.  Period 1 (Study Day 1) starts at time 0, and then the start time for e.g., Period 2, Day 8 would be time 168.  This ensures there will be one parameter set per individual for each dose event.  If this is not clear, please post an example of your dataset and we will take a look.  Perhaps I am not understanding what you are trying to do.

 

Best Regards,

 

Keith  

Thank you - this solved my problem






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