Phenytoin–Theophylline–Quinidine Interaction

Ronald C. Reed, Howard J. Schwartz, Frank J. Kroboth, Patricia Dowley Kroboth, Theodore Logan

Research output: Contribution to journalLetter

10 Scopus citations


To the Editor: Marquis et al. reported that the half-life of theophylline decreased from an average of 10.1 to 5.2 hours, with a subsequent increase in plasma theophylline clearance secondary to concomitant phenytoin therapy (Nov. 4 issue).1 We have also observed subtherapeutic theophylline levels, despite an apparently adequate dosage of theophylline, in patients treated with anticonvulsants. We studied three theophylline-dependent patients with asthma or bronchitis for three days on three separate occasions: when theophylline was administered concurrently with anticonvulsant therapy, one month after anticonvulsant therapy had been discontinued, and one month after anticonvulsant treatment had been reinstituted. After an overnight.

Original languageEnglish (US)
Pages (from-to)724-725
Number of pages2
JournalNew England Journal of Medicine
Issue number12
StatePublished - Mar 24 1983


ASJC Scopus subject areas

  • Medicine(all)

Cite this

Reed, R. C., Schwartz, H. J., Kroboth, F. J., Kroboth, P. D., & Logan, T. (1983). Phenytoin–Theophylline–Quinidine Interaction. New England Journal of Medicine, 308(12), 724-725.