Objective      To study the correlation between in vitro release of pyridostigmine bromide slow-release tablet and its in vivo pharmacokinetics.       Methods      Accumulative release percentage of pyridostigmine bromide slow-release tablet was assayed by ultraviolet spectroscopy with phosphate buffer as a dissolution medium according to the XD release assay in 2010 edition of Chinese Pharmacopeia. After 6 New Zealand rabbits were given a single oral dose of pyridostigmine bromide slow-release or conventional tablet

their serum drug

concentration was measured at different time points by HPLC-ultraviolet spectroscopy.       Results      The 12 h in vitro accumulative release rate of pyridostigmine bromide slow-release tablet was 98.6%.The main in vivo pharmacokinetic parameters for pyridostigmine bromide slow-release tablet were t

max

=4.001±0.004 h

C

max

=15.442±0.215 mg/L

and AUC

0-∞

=200.557±3.357. The correlation between the in vitro release of pyridostigmine bromide slow-release tablet and its in vivo pharmacokinetics was assayed with the Loo-Riegelman method. The linear regression equation for the in vivo accumulative absorption percentage and the in vitro accumulative release percentage of pyridostigmine bromide slow-release tablets was f

a

=0.485 1 f

r

+3.837 7

r=0.986 5

higher than the critical value r

6

0. 01

(P0.01) .       Conclusion      The in vivo release of pyridostigmine bromide slow-release tablet is significantly correlated with its in vitro release. The in vitro release of pyridostigmine bromide slow-release tablet can predict its in vivo pharmacokinetics.