# How to change dose intervals or activate/deactivate dose during simulations in SimBiology?

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Hanwen Wang on 18 May 2020
Commented: Hanwen Wang on 18 May 2020
I'm trying to simulate a Q3/4W dose regimen which administers a drug three times per 28-day treatment cycle. That is, I want a dose to be administered on day 1, 8, and 15 during each 28-day cycle for 15 cycles, so the dose intervals are not the same. Is it possible to change dose intervals during the simulation or deacctivate the dose after day 15 (in the first cycle) and reactivate it on day 1 for the second cycle? What is the best way to do it? Thank you!

Sietse Braakman on 18 May 2020
Hi Hanwen,
If I understand you correctly, you could follow one of two routes:
1. use three separate Repeat Doses. One for day 1, one for day 8, one for day 15. Then apply all three doses together in your simulation. This would be the best solution if you want to repeat the Q3/4W beyond 28 days, e.g. the 15 cycles you describe
2. use a single Schedule Dose and have a line for each dose. You could do this manually but that would be tedious for 15 cycles. You can make your life easier by click on "Editor" (circled in the attached screenshot) and give entries in MATLAB code for "Time", "Amount" and "Rate" (leave Rate empty if there is no associated rate with the dose amount). E.g.
time = repmat([1 8 15],1,15)
amount = repmat([100 200 300],1,15) % assuming dose at t = 1 is 100, t=8 is 200, t = 15 is 300.
rate = repmat([200 400 600],1,15)
Option 2 is probably the preferred solution if you only want a single dose object to deal with (as opposed to the 3 repeat doses from option 1.

#### 1 Comment

Hanwen Wang on 18 May 2020
Thank you!

R2020a

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