Enhanced Theophylline Clearance Secondary to Phenytoin Therapy

Abstract

This report describes two cases in which theophylline clearance accelerated markedly with concomitant phenytoin administration. Maximum calculated theophylline clearance ranged from 2½ to 3½ times baseline. Onset of the interaction began within five days of beginning concurrent therapy. With combined use, clinicians should be aware, when phenytoin is added, of the potential for reexacerbation of pulmonary symptomatology due to lowered serum theophylline concentrations.