Haloperidol Oxcarbazepine

Oxcarbazepine is a keto derivative of carbamazepine but offers several advantages over carbamazepine. Oxcarbazepine does not require blood cell count, hepatic, or serum drug level monitoring. It causes less cytochrome P450 enzyme induction than does carbamazepine (but may decrease effectiveness of oral contraceptives containing ethinyl estradiol and levonorgestrel). As opposed to carbamazepine, oxcarbazepine does not induce its own metabolism. These properties, combined with its similarity to carbamazepine, led many clinicians to use this medication for the treatment of bipolar disorder. Randomized controlled trials suggested efficacy in the treatment of acute mania compared with lithium and haloperidol, but these trials were quite small and did not include a placebo control (Emrich 1990). 

After first trimester carbamazepine, lamotrigine, oxcarbazepine, or valproate Second choice benzodiazepine (lorazepam) Third choice calcium channel blocker With psychosis first choice adjunctive high-potency typical antipsychotic (haloperidol, perphenazine, thiothixene, or trifluoperazine)... 

Haloperidol plasma levels are roughly halved by carbamazepine, phenobarbital and phenytoin. Bromperidol, fluphenazine and ti-otixene levels are also reduced by carbamazepine. The plasma levels of chlorpromazine and haloperidol do not appear to be affected by oxcarbazepine. Neurotoxicity has been seen with haloperidol and carbamazepine and haloperidol can raise serum carbamazepine levels. Valproate or valproic acid appear not to interact. 

A case report describes 3 schizophrenic patients taking haloperidol whose treatment was changed from carbamazepine to oxcarbazepine. After 2 weeks their plasma haloperidol levels had dramatically risen (from 6 to 18 nanomol/L, from 6 to 14 nanomol/L and from 17 to 27 nanomol/L). This was accompanied by severe extrapyramidal adverse effects, which necessitated dose reductions in 2 patients. ... 

Carbamazepine, phenobarbital and phenytoin are recognised enzyme inducers, therefore it seems highly likely that the reduced plasma bromperi-dol, chlorpromazine and haloperidol levels occur because their metabolism by the liver is markedly increased by these antiepileptics. Oxcarbazepine does not appear to interact, probably because it is not an enzyme indueer. 

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