Table 2.

Pharmacokinetics characteristics of AEDs which may increase the probability of problems associated with their generic substitution

AEDs	Therapeutic range	Pharmacokinetics parameters
		Narrow therapeutic range	Low water solubility	Nonlinear pharmacokinetics
Carbamazepine	4–12 μg/ml	Yes	Yes	Yes
Phenytoin	10–20 μg/ml	Yes	Yes	Yes
Valproate	50–100 μg/ml	Yes	No	Yes
Phenobarbital	20–40 μg/ml	Yes	No	No
Ethosuximide	40–100 μg/ml	Yes	No	Yes
Gabapentin	4–20 μg/ml	Yes	No	Yes
Lamotrigine	4–20 μg/ml	No	Yes	No
Levetiracetam	5–40 μg/ml	Yes	No	No
Oxcarbazepine	10–40 μg/ml	Yes	Yes	No
Topiramate	10–20 μg/ml	Yes	Yes	No
Tiagibine	100–300 ng/ml	Yes	No	No
Vigabatrin	0.8–36 μg/ml	Yes	No	No
Primidone	5–10 μg/ml	Yes	Yes	No
Felbamate	30–100 μg/ml	Yes	Yes	No
Zonisamide	10–40 μg/ml	Yes	Yes	Yes