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Chronic antiepileptic drug therapy: classification by medication regimen and incidence of decreases in serum thyroxine and free thyroxine index

Journal title
Therapeutic drug monitoring
Publication year
1987
Author(s)
Haidukewych, D.; Rodin, E. A.
Pages
392-8
Volume
9
Number
4

Results are described on the association of decreased serum total thyroxine (T4) and free thyroxine index (FTI) with antiepileptic drug therapy in a group of randomly selected chronically medicated outpatients (n = 291). For monotherapy subgroups (n = 164), the highest incidence (T4, 23.9%; FTI, 25.4%) of below normal values occurred in patients medicated with carbamazepine (CBZ), followed by phenytoin [(PHT) T4, 13.2%; FTI, 7.9%], and phenobarbital [(PB) (T4, 3.4%; FTI, 0%]. No T4 and FTI values below normal were detected in any patients (n = 30) on chronic valproic acid (VPA) monotherapy. For CBZ monotherapy (n = 67), women (n = 37) had a higher frequency of below normal values of T4 (p less than 0.05) and FTI (p less than 0.001) than men (n = 30). Therefore, the order of decreasing T4 and FTI effect was as follows: CBZ (women) greater than CBZ (men) greater than PHT greater than PB greater than VPA. For polytherapy subgroups (n = 127), the highest incidence (T4, 51.9%; FTI, 48.1%) was found in patients medicated with PHT and CBZ, followed by PHT and VPA (T4, 37.0%; FTI, 23.9%), and PHT and PB (T4, 17.2%; FTI, 10.3%). For PHT and CBZ poly-therapy (n = 52), women (n = 21) had a higher frequency of below normal values of T4 (p less than 0.05) and FTI (p less than 0.001) than men (n = 31). The magnitude of the decreasing T4 and FTI effect was greater for polytherapy subgroups (versus monotherapy subgroups) and in order as follows: PHT + CBZ (women) greater than PHT + CB (men) greater than PHT + VPA greater than PHT + PB.(ABSTRACT TRUNCATED AT 250 WORDS)

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