Effect of pregnancy on individual antiseizure medications
| Elimination | Decrease in serum concentration during pregnancy | |
| Carbamazepine | Hepatic | 0%–42% |
| Gabapentin | Renal—unchanged | Insufficient data |
| Lamotrigine | Hepatic glucuronidation | See table 4 |
| Levetiracetam | Renal >hydrolysis | 40%–60% |
| Oxcarbazepine monohydroxy derivative | Hepatic glucuronidation of active metabolite | 28%–36% |
| Phenytoin | Hepatic | 56%–61% |
| Phenobarbital | Hepatic | 50%–55% |
| Primidone | Derived from phenobarbital | 70% |
| Topiramate | Mainly renal—unchanged | 13%–40% |
| Valproate | Hepatic glucuronidation | 0%–28% |
| Zonisamide | Mainly hepatic, 15%–30% renal unchanged | 40%–50% |