Correlation of initial amitriptyline concentration reduction with activated charcoal therapy in overdose patients.

Plasma amitriptyline concentrations were measured serially in nine overdose patients and correlated with the timing and amount of each patient's initial activated charcoal therapy. A direct correlation was found between the time to initial charcoal therapy (Tc) and the plasma concentration half-life of amitriptyline (T 1/2) calculated for the first seven to 18 hours of hospitalization; T 1/2 = 2.68 + 0.047 Tc (r = 0.78, P less than 0.05). An inverse trend of T 1/2 with the initial amount of charcoal administered was also noted. Nortriptyline, the major metabolite of amitriptyline, decreased in two of three patients who received greater than or equal to 50 gm of activated charcoal within 60 minutes of presentation. These findings support previous in vitro and human volunteer studies advocating the rapid administration of activated charcoal in acute tricyclic antidepressant overdoses.