Carbamazepine lowers the 
plasma levels of 
mebendazole. 
Phenobarbital and 
primidone are expected to interact similarly. 
 When treating systemic worm infections it may be necessary to increase the 
mebendazole dosage in patients taking 
phenobarbital or 
primidone. Monitor the outcome of concurrent use. This interaction is of no importance when 
mebendazole is used for intestinal worm infections where its action is a local effect on the worms in the gut.