Therapeutic index and therapeutic window along with the ED50% ,TD50%, LD50% in case of new drugs using animal models but if you are comparing old drugs explain it i can help you you according to your needs
For example, Bisoprolol and Atenolol, which data would you gather to compare their safety? And which papers would you use to conclude which one is more safe? May you do it on Bisoprolol and Atenolol, and tell me which one is more safe, and how did you do it?
for the first concern of safety between two drug one parameter is LD50. this will allow to find toxicity level of drug and second is ED50. suppose two similar drug has A and B has LD50 1500 mg/kg and 2000 mg/kg. their therapeutic dose should not be reach 0.2 of LD50 that is 300mg/kg for A and 400mg/kg for B. however several possibilities could be there for efficacy of them. nay be B is effective equal to A in less dose that mean we dont need to give 0.2 LD50 of that so this is the mater of experiment which will let you know which drug is more effective and less toxic.