[Relevant inhibition of acetylcholinesterase with H2-receptor antagonists].

An inhibition of acetylcholinesterase activity by ranitidine and cimetidine as described by Hansen and Bertl (Z. Gastroenterol. 21: 164, 1983; Arzneimittelforsch. 33: 161, 1983) could only be confirmed by use of 1000-fold higher concentrations of the H2-antagonists (ID50 for ranitidine: 3,2 X 10(-4) M, for cimetidine: 3,1 X 10(-2) M) than those reported by the authors. The discrepancy may be explained by the fact that the authors did not consider the dilution factor in their method. In a typical therapeutic situation in 8 patients with ranitidine 150 mg twice daily and cimetidine 400 mg twice daily an inhibiton of the acetylcholinesterase could not be demonstrated. The inhibition of the acetylcholinesterase activity by H2-antagonists is of no practical relevance.