RAPID POTENTIOMETRIC DETERMINATION OF CHOLINESTERASES IN PLASMA AND RED-CELLS - APPLICATION TO EPTASTIGMINE MONITORING

Eptastigmine (MF 201) is a new physostigmine derivative with potent in hibitory activity on cholinesterases. Here we present a new potentiome tric cholinesterase activity assay suitable for MF 201 monitoring. The analysis is performed on a differential pH system and has the followi ng characteristics: (a) within-run precision: C.V. 2.0% (plasma cholin esterase), 1.8% (red cell cholinesterase); (b) between-run precision: C.V. 4.0% (plasma cholinesterase); (c) linearity: 1-10 kU/l (plasma ch olinesterase), 6-70 U/g Hb (red cell cholinesterase); (d) comparison w ith a reference method (x, HITACHI 737 Boerhinger Mannheim, Italy): y = 0.785x - 0.07; n = 37; r = 0.998. The assay has been applied to the determination of plasma and red cell cholinesterase activity in volunt eers over 60 years of age treated with a single oral dose of 30 mg ept astigmine. We found that red cell cholinesterase is selectively inhibi ted after MF 201 administration with the following kinetics (time, % o f inhibition, mean +/- S.E., n = 6): 0 h, 0; 1 h, 17 +/- 4.6; 2 h, 24 +/- 4; 4 h, 23 +/- 4.4; 12 h, 14 +/- 3. Eptastigmine plasma levels wer e also determined by a HPLC method: maximum concentration was found on e hour after drug administration.