The Effect of Route of Administration on the Cimetidine‐Theophylline Drug Interaction

Karl F. Cremer, John Secor, K. V. Speeg

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15 Scopus citations


The effect of route of cimetidine administration on cimetidine‐mediated inhibition of theophylline oxidation was examined in healthy individuals. Based on the evidence that cimetidine‐mediated inhibition of drug oxidation is competitive and, therefore, dependent on cimetidine concentration in the liver, oral cimetidine was tested to determine whether it would cause greater inhibition of drug oxidation than intravenous (IV) cimetidine. Both oral and IV cimetidine decreased theophylline clearance to the same extent. However, when clearance was corrected for cimetidine AUC, oral cimetidine resulted in a greater inhibition than IV cimetidine. Thus, the potential for increased inhibitory effect of oral cimetidine was balanced by decreased absorption after oral administration. Degree of inhibition (absolute change in theophylline clearance) and percent of inhibition after cimetidine correlated with the basal theophylline clearance. Individuals with higher basal theophylline clearances had greater degree and percent of inhibition than individuals with lower basal theophylline clearances. 1989 American College of Clinical Pharmacology

Original languageEnglish (US)
Pages (from-to)451-456
Number of pages6
JournalThe Journal of Clinical Pharmacology
Issue number5
StatePublished - May 1989

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)


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