The effect of paroxetine on thiothixene pharmacokinetics.
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.


METHODS
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.


CONCLUSIONS
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.
Guthrie
S K
SK
College of Pharmacy, University of Michigan, Ann Arbor 48109-1065, USA.
Hariharan
M
M
Kumar
A A
AA
Bader
G
G
Tandon
R
R
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001711:Biotransformation; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017374:Paroxetine / Q000008:administration & dosage / Q000494:pharmacology*; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D013888:Thiothixene / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D014150:Antipsychotic Agents; D017374:Paroxetine; D017367:Selective Serotonin Reuptake Inhibitors; D013888:Thiothixene