Well, in that case you need to get something like this
https://www.ebay.com/itm/Hot-Sales-...641063&hash=item3a90053bdd:g:TTgAAOxy039TO94-
Crush all the tablets you need there , create a fine powder ( as fine as you can ) then mix all that into the lotion ( don't use the lotion recipient, find something else ) mix it all, shake it really well, you can buy a magnetic stirrer and some laboratory glass. live it there for a couple of hours and then filter the lotion , you can buy some filters of simple the coffee ones , with that you will remove all the filler, since cetirizine and finasteride as solubles in the minoxidil lotion .
To calculate it how many pills, for example .
If you want a 1 % lotion of cetirizine and you use a 60 ml lotion of minoxidil :
100 ml --------------------1 gr of cetirizine
60ml ----------------------- X= 0.6 gr of cetirizine.
So, that is 600mg of cetirizine every 60 ml of minoxidil to make a 1 % of cetirizine, simple use 60 pills of 10mg cetirizine.
Same math for whatever concentration you want to use for finasteride.