If you have no idea about the absorption via the skin or the needed dose transdermally, I Think you will need to formulate the drug in many possible doses and assess these Formulations in vivo to maintain the needed plasma concentrations.

Hope this helps

Hi lomass,

I hope you are well

At first, it is a research or product in R&D

If you fix doses form of any product!?

You question is complex.

You get assay your product according pharmacoaup USP,BP

Then the stability 1,2 months for research

And for product in industry

You should be 3 batches after R&D

In skale up

The stablity test so crucial initial, 3,6months.

There is no conversion factor for deciding the topical dose. It depends on the following factors related to

a) Drug's physicochemical properties

b) Location, type, and area of skin for the administration of the drug

c) Conditions of the skin (normal or diseased)

d) Formulation characteristics and type of chemicals used

But for sure it would be higher than the oral dose if it is intended for systemic absorption.