Anesthesiology
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Aqueous suspensions of the local anesthetic n-butyl-p-aminobenzoate (BAB), epidurally applied in terminal cancer patients, resulted in a sensory blockade, lasting up to several months. To investigate the mechanism of action on the cellular level, the effect of 100 microM BAB on Na+ action potentials and on Na+ currents in dorsal root ganglion neurons from neonatal rats was studied. ⋯ BAB dramatically increased the firing threshold, and in part of the sensory neurons, it blocked the action potential. The inactivation of the fast Na+ channels, but not of the slow Na+ channels, was increased by BAB. Thus, the block of fast Na+ channels by BAB may contribute to epidural analgesia. At exposure times of 10 min, the effect of BAB was not reversible. This probably originates from its high lipid-solubility, which may be an important factor in determining the duration of the block in vivo.