Ethosuximide drug interactions

Carbamazepine also can induce the enzymes that metabolize other anticonvulsant drugs, including phenytoin, primidone, phenobarbital, valproic acid, clonazepam, and ethosuximide, and metabolism of other drugs the patient may be taking. Similarly, other drugs may induce metabolism of carbamazepine the end result is the same as for autoinduction, and the dose of carbamazepine must be readjusted. A common drug-drug interaction is between carbamazepine and the macrolide antibiotics erythromycin and trolean-domycin. After a few days of antibiotic therapy, symptoms of carbamazepine toxicity develop this is readily reversible if either the antibiotic or carbamazepine is discontinued. 

Administration of ethosuximide with valproic acid results in a decrease in ethosuximide clearance and higher steady-state concentrations owing to inhibition of metabolism. No other important drug interactions have been reported for the succinimides. 

Ethosuximide. This succinimide is relatively safe from side effects and drug interactions. 

I Drug Interactions. Because ethosuximide is not protein bound, displacement interactions cannot occur. The metabolism of ethosuximide may be induced by carbamazepine. A complex interaction between valproic acid and ethosuximide has been reported. Valproic acid may inhibit the metabolism of ethosuximide, but only if the metabolism of ethosuximide is near saturation. ... 

The concurrent use of antiepileptics is common and often advantageous. Information on these interactions is sparse and even contradictory and their clinical importance is uncertain. Nevertheless, good monitoring would clearly be appropriate if these drugs are used with ethosuximide to monitor for potential toxicity and to ensure adequate seizure control. 

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