Comparison of the kinetic interactions of the neuroleptics perphenazine and zuclopenthixol with tricyclic antidepressives.

Using data from a therapeutic drug monitoring database, kinetic interactions between the neuroleptics zuclopenthixol and perphenazine and tricyclic antidepressives were studied. Out of 290 patients monitored for amitriptyline and 611 patients monitored for nortriptyline, 77 patients were comedicated with perphenazine and 50 patients with zuclopenthixol. Comedication with perphenazine increased the median steady-state serum concentration to daily dose ratio (C/D) of nortriptyline by 30-45%, whereas the median C/D of amitriptyline was unaffected. On the contrary, median C/D values of nortriptyline and amitriptyline were not significantly influenced by comedication with zuclopenthixol. Thus, in accordance with previous studies, perphenazine increases the concentration of tricyclic antidepressives to a moderate extent. Zuclopenthixol, on the other hand, does not exert any impact under routine therapeutic drug monitoring, even though the drug is known to partly depend on metabolism by the isozyme cytochrome P450 2D6.