<p>Isoniazid may increase the serum concentration of ethosuximide, leading to toxicity. Antipsychotics, antidepressants, MAOIs, and mefloquine may antagonise anticonvulsant effects of ethosuximide. Plasma conc of ethosuximide may be reduced by carbamazepine, phenobarbital, phenytoin, and primidone; and affected by valproate. Chloroquine or hydroxychloroquine may increase risk of convulsions. Isoniazid.</p>