Discrimination Between Patterns of Drug Exposure by Toxicological Analysis of Decomposed Skeletal Tissues. Part II: Amitriptyline and Citalopram

Decomposed bone and plasma samples of rats exposed to amitriptyline (AMI) and citalopram (CIT) under different dosing patterns were analyzed. Wistar rats received one acute dose (120 mg AMI/kg and 40 mg CIT/kg; n = 5) or two doses (40 mg AMI/kg and 13 mg CIT/kg, n = 5) 40 min apart. After collection of perimortem blood, the rats were euthanized and placed outdoors to decompose to skeleton. Recovered bone was ground and subjected to methanolic extraction. Bone extracts and plasma samples underwent solid-phase extraction and were analyzed using ultra-high-performance liquid chromatography. Concentrations of drugs and the primary metabolites [nortriptyline (NORT), desmethylcitalopram (DMCIT) and didesmethylcitalopram (DDMCIT)] were expressed as mass-normalized response ratios (RR/m). Concentrations (RR/m) of AMI, CIT and metabolites did not differ significantly between exposure types in plasma and all bone types examined or for the pooled bone samples (P > 0.05). However, ratios of concentrations of NORT to those of AMI differed significantly between exposure patterns for all bone types except for rib (P < 0.05). Values of DMCIT/CIT differed significantly between exposure patterns in rib, pelvi and femora (P < 0.05). Values of DDMCIT/CIT did not differ significantly between exposure types (P > 0.05), while those of DDMCIT/DMCIT were significantly different for all bones except the vertebrae and rib (P < 0.05).