Abstracts

Rationale: Our previous investigation demonstrated that conversion from the inducers phenytoin (PHT) or carbamazepine (CBZ) to the non-inducing drugs levetiracetam (LEV) or lamotrigine (LTG) lowers C-reactive protein (CRP). Declines in homocysteine (HCY) occurred only in patients removed from PHT, not those withdrawn from CBZ, however. We sought to determine if similar results would occur when patients are switched to topiramate (TPM) and to acquire additional data to ascertain the effects of individual antiepileptic drugs (AEDs) on CRP, HCY, and B-vitamin levels. Methods: We converted 13 patients from inducing AEDs to TPM (daily doses of ?150mg except for one patient). CRP, HCY, serum folate, pyridoxal phosphate (B6) and vitamin B12 levels were drawn before and 6 weeks after the switch. These data were then pooled with the previous study (of 34 patients switched to LEV or LTG and 16 normal subjects) to provide greater power to discern the effects of individual drugs. We did additional analyses to determine whether B vitamin deficiency was more common in patients treated with inducing agents. Results: Conversion from inducers to TPM reduced CRP by 59% (p<0.001) and increased folate by 4 ng/ml (p=0.003); HCY remained unchanged. Frank B6 deficiency (<5 ng/ml) was observed in 8 of 11 inducer-treated patients (72%); this resolved in 5 of 8 after switch to TPM. When pooled with the previous data, significant declines in CRP occurred after drug switch irrespective of which inducer the patient had been taking (-45%, p?0.002). Folate rose more prominently in patients withdrawn from PHT ( 3.6 ng/ml, p=0.002) than in those withdrawn from CBZ ( 1.8 ng/ml, p=0.075). HCY declined only in the patients taken off PHT (-2.6 umol/L, p=0.003), not in patients withdrawn from CBZ ( 1.0 ng/ml, p>