I determined the sample size already (25), but I want to know if it has to be increased because of a minor change. Our study consists of two groups - one will be sedated and the other will not. For the group that will be sedated, three drugs will be used. One of those three drugs (K) can be replaced by another drug (P) that does the same thing. If patients prefer, P can be used instead of K (original plan was to use K for everyone, but we decided to have P as an option/alternative treatment). The PI asked me if it's possible to use K for half of the patients and P for the other half or something like 15 receiving K and 10 receiving P where the total still remains as 25 for each group. Is it okay to keep the sample size as 25 for each group or will the sample size have to increase if the sedated group uses P for some patients instead of K? I should probably add that all of the drugs that will be used in this study have already been approved and marketed. We are simply comparing two types of anesthesia techniques. It makes sense to increase the sample size (maybe double it?), but I am not sure how to determine if it requires doubling or something else because the study design didn't change for the non-sedated group (only one of the drugs in the sedated group will/might be varied).
Please let me know what you think. I appreciate any help you may have.