Alchemist, Injection spear, streching out potions or getting attack extracts

[Zwordsman]

Set Up: Injection spear, Alchemist, potion of offensive spell (shocking grasp probably)

So. My question for hope for advice.

Does anyone know ways to stretch potions for the injection spear use? When you stab someone with an Injection Spear you can inject apotion. Which is neat for a specialty twist for those "big moments" or as a costy "oomph" moment. So I was wondering ways to stretch out my potion costs a bit. Particularly early game.

Or if anyone knows of a way to get any attack spells on to the alchemist's extract list? Like shocking grasp or inflict wounds. etc.
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At first I thought alchemcial allocatin would work.. But you are effect. So I can't just pour alchemical allocation into the injection spear mix with the potion of X and get the potion bak. Sadly

The only other way I can see of stretching potions when using for this purpose is Dilute Potion discovery. Which gives me another potion for 1/4th cost.

So I could get (at level 12) two potions of C5 shocking grasp for 250+62.5 gold. Which is fun for level 12 and up.

But are there any options for lower levels? (or games without much money inflow)

Not remotely efficient no.. but highly amusing.

Edit:
Polypurpose pancea sadly doesn't work (thought the effect was decided at the time of creating the extract)
Skinsend will work. Granted once it is that perons' turn they can just return their skin to them... so unless someone is standing by to full round coup de grace it is less useful

[SAMAS]

I think you need the Infusion discovery to give Extracts to someone else. In which case, you would then chose extracts that are beneficial under certain circumstances, and use them any time but then, like Reduce Person on an Ogre, or Polymorphing someone into a form that can't use their weapons.

[The Toaster]

I've always liked Extracts of detonate - but then I would deliver them with Poisoners Gloves...