Treating the sides and back of the head with Topical finasteride

I have diffuse and frontal mpb. I measured the thin hairs on the back and the sides with a digital microscope. Around 15-20% of the area is composed of thin hairs. I am on topical finasteride and min. My doctor didn’t say that I should apply the fin on the sides/back, but I think I have to. Do you think it is essential? I also apply min to all the scalp area.

It makes no sense to apply finasteride to the sides and back which is the area that balding usually does not occur. Also, if you use topical finasteride and spread it around your entire head (including the permanent zone around the sides and back of your head), enough systemic absorption might occur just as if you took the oral pill, defeating your goal to keep it topical. Normally the liposomal topical finasteride has at most an 18% absorption through the skin in the body while other non-liposomal finasteride preparations might have more systemic absorption.