Phenytoin glucuronide conjugate

Unfortunately, the elimination of some drugs does not follow first-order kinetics. For example, the primary pathway of phenytoin elimination entails initial metabolism to form 5-(parahydroxyphenyl)-5-phenylhydantoin (p-HPPH), followed by glucuronide conjugation (Figure 2.8). The metabolism of this drug is not first order but follows Michaelis-Menten kinetics because the microsomal enzyme system that forms p-HPPH is partially saturated at phenytoin... 

Oxcarbazepine (Trileptal) (10,ll-dihydro-10-oxocar-bamazepine) is a keto analog of carbamazepine. Oxcarbazepine functions as a prodrug, in that it is almost immediately converted to its main active metabolite, a 10-monohydroxy derivative, which is inactivated by glucuronide conjugation and eliminated by renal excretion. Its mechanism of action is similar to that of carbamazepine. Oxcarbazepine is a less potent enzyme inducer than is carbamazepine, and substitution of oxcarbazepine for carbamazepine is associated with increased levels of phenytoin and valproic acid, presumably because of reduced induction of hepatic enzymes. Oxcarbazepine does not induce the hepatic enzymes involved in its own degradation. Although oxcarbazepine does not appear to... 

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