Effects of neostigmine and edrophonium on human erythrocyte acetylcholinesterase activity

Erythrocyte acetylcholinesterase (AChE) activities in vivo were measured over 60 min using a spectrophotometric method after administration of neostigmine or edrophonium for antagonism of pancuronium-induced neuromuscular block in 31 patients. Erythrocyte AChE activities decreased to 11.3 (SD 1.2)% and 11.4 (0.8)% of baseline values (P less than 0.001) within 2 min, then recovered slowly and were 43.2 (6.2)% and 27.9 (2.9)% (P less than 0.001) 60 min after administration of neostigmine 0.036 mg kg-1 and 0.071 mg kg-1, respectively. However, the enzyme activity after edrophonium 1.43 mg kg-1 did not change significantly over 60 min. The results suggest that mechanisms other than AChE inhibition may be responsible for the anti-curare effect of edrophonium.