we picked up the dose of drugs for different animal models, based on the previous studies. and also we use the articles ' Guidelines on dosage calculation and stock solution preparation in experimental animals' studies' and  'Guideline on dose level ....'

Pls find attached

Best Regard

You could also do a maximum tolerated dose study depending on the mechanism of your drug of interest.

I am also carefull about the administration route, I choose high dose for peroral than intraperitoneal route. 

I check Merck index or relevant databases for LD50 dose and

Lastly, get some idea from human dose per / kg. Sometimes it is sad to see more than  100 fold medicine given to animals that normally we never use it in routine practice for treatment, experiment should not be too far away from daily life.  I mean any medicine can be posion depend on doses (paracelsus)

It is always better to work at least 2 doses, low and high. I usually prefer 3 fold between them (eg. 3 mg, 10 mg, 30, 100, 300; resemblences to logaritmic curve).