Theophylline levels are decreased. Xanthine derivatives are used as bronchodilators in asthmatic patients. Administration of rifampin along with xanthine derivatives causes increased metabolism of theophylline, which results in decreased levels of theophylline. Additive cardiac and central nervous system stimulation is produced when caffeine is administered along with theophylline. More test answers on https://studyhippo.com/chapter-36-37/