The effect of furosemide and bumetanide on cerebrospinal fluid formation.

Complete inhibition of carbonic anhydrase maximally reduces CSF flow 40-60%. We have confirmed that CSF flow in rabbits may be maximally decreased in this way by acetazolamide 30 mg/kg i.v., but have found only about 20% reduction from control after furosemide at 50 mg/kg i.v. This effect of furosemide is consistent with specific but partial inhibition of carbonic anhydrase of choroid plexus (and perhaps other sites of CSF secretion) based on the affinity of furosemide for carbonic anhydrase. Bumetanide, with 7 times lower affinity for carbonic anhydrase and 14-40 times higher inhibition of renal electrolyte transport processes than furosemide, did not decrease CSF flow.