Blood Concentrations of Amitriptyline and Its Metabolite in Rats after Acute Oral Administration of Amitriptyline

Amitriptyline (AMT), a tricyclic antidepressant that is a dibenzocycloheptadine derivative, is frequently used. However, the case reports of AMT-related fatalities are increased, nowadays, due to the low levels of toxic and fatal concentration in blood. So, this study was carried out to determine the concentrations of AMT and its demethylated metabolite, nortriptyline (NTR), after acute single oral administration of AMT in rats. Blood samples were collected five times from the ophthalmic venous plexus at 0, 1, 2, 4, and 8 h after acute single oral administration of AMT in toxic doses of 10 (Group I) or 20 mg/kg (Group II), and the concentrations of AMT and NTR and the mean ratios of AMT to NTR (AMT/NTR) in the blood were periodically determined at designated times. The blood concentrations of AMT and NTR were identified and quantitated by gas chromatography with thermionic specific detection and gas chromatography-mass spectrometry after solid-phase extraction with a Clean Screen DAU column. The peak blood concentrations of AMT and NTR in Group I were 0.34 and 0.28 microg/mL, respectively, and those of AMT and NTR in Group II were 0.59 and 0.43 microg/mL, respectively, and were reached at 1 h after single oral administration.