Pharmacokinetics of desipramine in Asian and Caucasian volunteers

The pharmacokinetic differences of tricyclic antidepressants (TCAs) in Asians and Caucasians remain controversial. Thirty-seven age-matched healthy volunteers (18 Asians and 19 Caucasians) ingested a single desipramine (DMI) dose of 1.0 mg/kg of body weight. Blood was obtained at 1, 3, 5, 7, 12, 24, 48, 72, and 96 hours after dosing. Serial 24-hour urine samples were collected for 5 days. There were no statistically significant differences in plasma levels between the two groups. DMI concentrations peaked a median of 5 hours after ingestion in Asians vs. 3 hours in Caucasians. Total clearances of DMI (CL DMI) and hydroxylated DMI (OH-DMI) were greater in Caucasians. These differences were no longer significant when corrected for body weight. Clearances appeared to follow tri-modal distributions. The proportions of Asians and Caucasians falling into the slow, intermediate, and rapid clearance groups were not significantly different, but there was a tendency for more Caucasians to be in the rapid clearance group.