Effect of phenobarbital on the disposition of intravenous theophylline

The disposition of intravenous doses of theophylline was determined in normal male subjects before and after treatment with phenobarbital 2 wk. Although there was some variation in disposition of the 2 drugs, there were no significant effects of phenobarbital on theophylline kinetics. We conclude that theophylline dosage need not be altered during concomitant administration of phenobarbital.