Stability of estazolam in dog tissues preserved in formaldehyde solution

Objective To investigate the stability of estazolam in biological samples preserved in formaldehyde solution.Methods The dog was given intragastric administration of estazolam with a dose of 37.6 mg/kg and killed 2 h later.Heart,liver,kidney and brain of the dog were cut up into 1 g and preserved in 4% formaldehyde solution respectively.The content of estazolam in biological samples and formaldehyde solution were analyzed by HPLC at different times.Results The content of estazolam in heart,liver,kidney and brain or in formaldehyde solution reduced gradually followed with the extention of preservation time.At the 63 th day,estazolam content in four tissues were 0.8%,1.7%,1.0% and 2.2% of the original content respectively.Conclusion Estazolam in tissues can diffuse into formaldehyde solution and decomposed quickly,so biological samples contained estazolam should not be preserved in formaldehyde solution.