This medication is metabolized by demethylation and oxidation; the primary metabolite is
nordoxepin (N-desmethyldoxepin), which later undergoes glucuronide conjugation.
Other drugs assayed at therapeutic concentrations that had no interference included carbamazepine and its epoxide and hydroxy metabolites, oxcarbazepine and it monohydroxylated metabolite, zonisamide, levetiracetam, phenytoin and its metabolites, felbamate, lamotrigine, clonazepam, phenobarbital, primidone, acetaminophen, salicylate, ibuprofen, amitriptyline, nortriptyline, desipramine, doxepin and
nordoxepin, imipramine, valproic acid, topiramate, mephenytoin and Nirvanol, amiodarone and desethylamiodarone, methsuximide and normethsuximide, ethotoin, clozapine, and sertraline.
In several cases, the following substances were detectable only after cleavage of conjugates: oxazepam, temazepam, lormetazepam, morphine, codeine, hydroxypromethazine, norhydroxypromethazine,
nordoxepin, norhydroxydoxepin, hydroxytrimipramine, viloxazine, or hydroxyviloxazine.