Monster Hunter Freedom

First , buy a power seed from the old saleslady. Then , combine honey and bitterbug or just buy catalyst , then combine power seed and catalyst. Make sure Book of Combos is in your inventory.

HONEY + BITTERBUG (Bitterbug can be found when you try to net bugs in the Kokoto farm)
NEXT,
You will get CATALYST.
NEXT. BUY A POWER SEED FROM A SELLER IN TOWN.
COMBINE CATALYST WITH POWER SEED.
YOU WILL GET DEMONDRUG, but save your game BEFORE you combine, in case if you get GARBAGE as your result!

My cats gave me sometimes demondrugs.

You can also use a book of combos to augment the chances of the combininaton succed.

I usually just make them instead of waiting to get them

There's a few ways. First, combine Power Seed with Catalyst. They're found in battle and randomly through the old lady vendor, respectively. But if you can beat Khezu, use it's Pale Extract to make Demondrug better. The combos have a high chance of failing, so have all five combo books and an armour that raises it's chance of success :D Good luck :D

Demondrug=Powerseed+catalyst
Catalyst=Honey+Bitterbug
Megademondrug=Demondrug+Power Extract

~~~Powerseed + Catalyst = Demondrugs~~~