Abstracts

Rationale: Studies have shown that enzyme inducing antiepileptic drugs including carbamazepine (CBZ) interact with thyroid function, while lamotrigine (LTG) has no effect. So far, no information exists regarding levetiracetam (LEV). The aim of this study was to investigate possible changes in thyroid hormone function in patients using CBZ, LTG or LEV as monotherapy for epilepsy, and to compare the results with a group of healthy controls. Methods: 102 female and 133 male patients and 80 controls (44 females, 36 males) within an age range of 18 to 45 from Norway and Austria were included. They had been treated with LEV (27 females, 32 males), CBZ (31 females, 63 males) or LTG (45 females, 38 males) as monotherapy for at least 6 months. Thyroid stimulating hormone (TSH), free tri-iodothyronine (fT3) and free thyroxine (fT4) levels were measured in serum. Results: In women using CBZ, fT3 and fT4 were significantly reduced compared to controls (4.5 and 12 pmol/L vs 5.1 and 16 pmol/L, respectively. P<0.001 for both). TSH was lower than in the control group (1.4 vs 1.95 mIE/L), but the difference was not significant. No significant changes in thyroid function were seen in women taking LEV or LTG compared to controls. In men using CBZ, both fT3 and fT4 were significantly reduced compared to controls (5.2 and 14.0 pmol/L, vs 5.8 and 17.0 pmol/L, respectively. P<0.001 for both). In males treated with LEV or LTG, fT4 showed a small, but significant reduction versus controls (LTG treated 15.0 pmol/L; LEV treated 15.0 pmol/L, controls 17.0 pmol/L. P= 0,024 and 0,008, respectively). TSH and fT3 were not influenced by LEV or LTG.