# Sample size calculation for clinical trial

I am facing a problem regarding sample size calculation of clinical trial.

Currently a drug is used at 2.5 mg for adult and 1.5 mg for children and death rate is 0. Now we want to reduce the drug level to 1.0 mg for adult and 0.5 mg for children.

If I want to keep the death rate at same for new drug level then how many sample should we take to justify.