Interactions between tagamet(cimetidine) and Aminophylline extended release (aminophylline)
cimetidine and aminophylline (Moderate Drug-Drug)
MONITOR: Cimetidine may increase theophylline plasma concentrations by as much as 70%. The mechanism is related to inhibition of liver CYP450 enzymes responsible for theophylline metabolism. Although controlled studies have not demonstrated an interaction with ranitidine, famotidine, or nizatidine, and they do not have enzyme-inhibiting properties, there have been rare case reports of increased theophylline concentrations and/or toxicity with each of these agents. Patients with chronic obstructive pulmonary disease, congestive heart failure, or cirrhosis may have slower theophylline clearance rates; therefore, they may be at greater risk of developing theophylline toxicity.
MANAGEMENT: Clinical monitoring of patient response, tolerance, and laboratory theophylline serum concentrations is recommended. Patients should be advised to report any signs of theophylline toxicity including nausea, vomiting, diarrhea, headache, restlessness, insomnia, or irregular heartbeat to their physician.
