Vehicle solutions for sparingly soluble drugs intrathecally?

Experimental Techniques
1

I want to deliver some small molecule compounds intrathecally to mice. Ideally, a compound is fully soluble in PBS or 0.9% saline, and requires nothing further. But I have some sparingly soluble compounds that need to be coerced into something besides DMSO. I’ve tried a number of possible vehicles, and here is what I’ve got:

  1. 20% DMSO + PBS
  2. 10% DMSO + 0.5% Tween-80 + PBS
  3. 5% Tween-80 + PBS

Right now, my compound doesn’t like anything but 5% Tween 80. I can get down to 2.5% and it’s OK. I’ve seen people do this in the literature with as much as 10% Tween for Capsaicin. This is not ideal, since I’m concerned about nonspecific effects of the vehicle. Of course I’ll do the control, but I’d like to hear people’s experiences here. Which of these is least bad? Any other options?

References

  1. 2% Tween-80, 15% DMSO, 83% Saline for CB1 agonist
  2. 10% Tween-80, 10% Ethanol, 80% saline for i.t. capsaicin
  3. 5% Tween 80 for PLA2 agonists, i.t.