Zonisamide Primidone

Partial seizures Carbamazepine Phenytoin Lamotrigine Valproic acid Oxcarbazepine Gabapentin Topiramate Levetiracetam Zonisamide Tiagabine Primidone, phenobarbital Felbamate... 

Enzyme-inducing antiepileptic drugs (carbamazepine, phenytoin, phenobarbital, and primidone) may decrease plasma levels of zonisamide... 

Phenobarbital Phenytoin Primidone Felbamate Lamotrigine Tiagabide Topiramate Valproate Zonisamide Clobazam Clonazepam Diazepam usually compensated by the effect of the added drug risk of toxicity when interfering drug is discontinued drug... 

Primidone use Is associated with decreases In CBZ, lamotrigine, valproate, tiagabine, and zonisamide serum levels. Primidone levels are increased by nicotinamide and Isonlazid. Hydantoins increase the plasma concentrations of primidone, phenobarbital, and PEMA. CBZ Increases levels of phenobarbital derived from primidone. Primidone levels are decreased by succinimides, CBZ, and acetazolamide. 

Phenobarbital, phenytoin and carbamazepine can cause a small to moderate reduction in the serum levels of zonisamide, while lamotrigine may increase zonisamide levels. Clonazepam and valproate have little or no effect. Zonisamide shows variable effects (a modest decrease, an increase, or no effect) on carbamazepine serum levels, but has no important effect on lamotrigine, phenobarbital, primidone or valproate levels. Most studies also suggest that zonisamide has no effect on phenytoin levels, but two showed a modest increase. 

In one study the ratio of plasma level to dose of zonisamide was 29% lower in 11 patients also taking phenobarbital than in 28 patients taking zonisamide alone, suggesting that phenobarbital reduces zonisamide levels. Similarly, another study in healthy subjects found that pretreatment with phenobarbital increased the clearance of a single dose of zonisamide by about twofold. A further study found no changes in the serum levels of phenobarbital or primidone in 34 and 13 patients, respectively, who were also given zonisamide. ... 

Commercial immunoassays have long been available for the classic anticonvulsants such as phenytoin, carbamazepine, valproic acid, primidone, and ethosuximide and generally provide useful results under normal TDM conditions. Kits for the newer anticonvulsants such as lamotrigine, gabapentin, zonisamide, and levetiracetam have become available only recently so their effectiveness in monitoring in a broad population cannot yet be evaluated. While targeted immunoassay can be a very efficient and cost-effective way... 

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