[The solubility of bupivacaine in cerebrospinal fluid (author's transl)]

The precipitation of different local anaesthetics was studied spectrophotometrically in vitro. Bupivacaine-HCl precipitates at a pH of 7.4 of the cerebrospinal fluid when the concentration is 0.75 mg/ml. The bupivacaine-solution with admixture of epinephrine is not associated with turbidity up to 2.5 mg/ml. The CO2-preparation of bupivacaine shows no decrease of extinction. Mepivacaine, lidocaine and carticaine do not precipitate at the range of CSF-pH from 6.9 up to 9.0. The relevance for clinical use is discussed. After intrathecal application of less than 15 mg bupivacaine-HCl of a 0.5% solution, no precipitation will occur. Since the volume of distribution in the subarachnoidal space is lowered after application of hyperbaric local anaesthetic solutions, the possibilities of precipitation are enhanced.