Pentobarb Anesthesia

Larry P. Gonzalez f628 at
Mon Sep 25 10:13:49 EST 1995

I need some info about the free-acid form of pentobarbital.

We have  been using sodium pentobarbital for anesthesia in rats, but
recently ran out.  Since we had some of the free-acid form in the lab,
I tried substituting that for the salt, adjusting for differences in
molecular weight.  The acid is not soluble in water, but will readily
dissolve in 95-100% ethanol.   Therefore,  I administered about
38mg/kg of the free-acid dissolved in ethanol to 300g rats.  This
produced a solid level of anesthesia and animals recovered nicely, and
they appeared healthy initially.  However, all of the animals
receiving this preparation have died within 2 to 4 days of

Can anyone shed some light on what is going on?


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