Change in treatment from oral finasteride to 1% solution. Is there a reasonable dosage?

oral finesteride cannot even be compared to topical they do not have the same comparison or results. but you can use topical along with oral supplements, topical growth factors and prp/acell in office. see link to emeragecosmetics.com daily protocol and weekly rolling.
I suggest a formal consultation as there are a combination of treatments that can be done to improve har loss.  Oral finesteride has very little to no side effects in the majority of people; PRP/platelet-rich plasma + stem cells like A Cell help regrow hair and slow down the thinning process; rogaine and restorsea spray should be used daily; oral viviscal helps keep nutrients high in the follices as well.  Transplantation is a last resort but works early in the aging process as well.  A formal consultation and combination treatment is needed.  Best, Dr. Emer. 

Androgenetic Alopecia is caused by an inherited genetic enzyme defect that results in too high levels of DHT made worse by lifestyle and nutrition.  The defective enzyme: 5-alpha-reductase is produced by the body in 2 places, the prostate and circulated around the body through the blood stream, and on the scalp.  This is why a single treatment method id generally ineffective.  At Stop and Regrow we use both topical and oral formulas together that include supplements specifically targeted to repair the defective 5-alpha-reductase and reduce DHT production in both the prostate and at the scalp back to normal levels.You can read more about propecia/finasteride and why it isn't effective below.

I recommend 0.1% topical finasteride in a liposomal compounding so that the drug stay in the skin and little moves into your body. When you stop the oral, if there is any area not touched by the topical yet impacted by the oral finasteride then you could lose hair in those area