Effect of carbamazepine and valproic acid monotherapy on thyroid function tests in epileptic patients

Objectives: This study was conducted to assess the effect of carbamazepine (CBZ) and sodium valproate (VPA), as a monotherapy in epileptic patients, on thyroid function tests as assessed by serum total triiodothyronine (TT3), total thyroxine (TT4) and thyroid stimulating hormone(TSH). Subjects and methods: Sixty three epileptic patients using monotherapy were included in the study. These included 44 patients using CBZ and 19 using VPA. A control group of 47 apparently healthy individuals were also included in the study for comparison. Measurement of TSH, TT3 and TT4 was done using Gamma counter.Results: The results of this study revealed that patients on CBZ showed significantly decreased mean level of TT4 in comparison with the control group (P<0.01), while mean TT3 and TSH levels showed statistically insignificant differences from the control group (P>0.05). In the VPA group, mean TT3, TT4 and TSH values showed insignificant differences from the control group (P>0.05).Conclusion: Unlike VPA, CBZ significantly decreases level of TT4 without affecting TT3 and TSH levels. Keywords: Carbamazepine, sodium valproate, thyroid function tests.