The effect of paroxetine on thiothixene pharmacokinetics.

Author(s): Guthrie SK, Hariharan M, Kumar AA, Bader G, Tandon R

Affiliation(s): College of Pharmacy, University of Michigan, Ann Arbor 48109-1065, USA.

Publication date & source: 1997-06, J Clin Pharm Ther., 22(3):221-6.

Publication type: Clinical Trial; Randomized Controlled Trial

OBJECTIVE: In this study healthy volunteers received thiothixene with and without a 3-day pretreatment with paroxetine to determine if paroxetine decreased the clearance of thiothixene. METHOD: Ten healthy medication-free volunteers (4 women and 6 men, mean age 38 +/- 12 years) were randomized to receive a single 20 mg oral dose of thiothixene on two separate occasions. On one occasion thiothixene was given concurrently, and following 3 days of pre-treatment with oral paroxetine (20 mg/day). On the other occasion thiothixene was given without paroxetine pre-treatment. The two study days were separated by a minimum period of 2 weeks. On both study days, after the administration of thiothixene, 10 ml blood samples were collected over the next 72 h. RESULTS: None of the pharmacokinetic parameters of thiothixene were significantly altered by a 3-day treatment with paroxetine. DISCUSSION: It is likely that the CYP2D6 isoenzyme is not responsible for a high proportion of thiothixene clearance, but one cannot exclude the possibility that a longer paroxetine pretreatment might have caused some inhibition of thiothixene clearance.