CORTICOSTEROIDS AND PHENOBARBITAL

The therapeutic effects of systemic dexamethasone, methylprednisolone, predniso- lone and prednisone are decreased by phenobarbital. Other barbiturates (including primidone) probably interact similarly, although direct evidence is lacking. The dexamethasone adrenal suppression test may be expected to be unreliable in those taking phenobarbital.
Prednisone and prednisolone appear to be less affected and therefore may be preferred. Monitor concurrent use to ensure corticosteroid efficacy.