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Possible drug-drug interaction between quetiapine and lamotrigine--evidence from a Swedish TDM database
Marine L Andersson1, Linda Björkhem-Bergman, Jonatan D Lindh
1Department of Laboratory Medicine, Division of Clinical Pharmacology, Karolinska University Hospital, Huddinge, Karolinska Institutet, 141 86 Stockholm, Sweden. marine.andersson@karolinska.se
Aim:
The aim of the present study was to investigate a previously proposed interaction between quetiapine and lamotrigine resulting in reduced serum quetiapine concentrations.
Methods:
Data on 402 patients subjected to analysis of quetiapine concentration in serum were extracted from a routine therapeutic drug monitoring database. Among these patients, those concomitantly treated with lamotrigine (n= 22) were identified and matched with 22 controls receiving quetiapine while unexposed to lamotrigine. The dose-corrected quetiapine concentrations (C : D ratios) in the two groups were compared in both paired and unpaired analyses.
Results:
Patients co-treated with lamotrigine had a lower mean C : D ratio (0.71, 95% CI 0.46, 0.97) compared with controls (1.64, 95% CI 1.00, 2.28). Dose-corrected quetiapine concentrations were 58% lower in patients co-medicated with lamotrigine.
Conclusions:
This study indicates that lamotrigine exposure is associated with substantially reduced serum concentrations of quetiapine, possibly due to induced glucuronidation. These findings need to be confirmed in experimental studies.
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