OBJECT DRUGS

• Theophylline

PRECIPITANT DRUGS

Enzyme Inhibitors:

• Atazanavir (Reyataz)
• Cimetidine (Tagamet, etc.)
• Disulfiram (Antabuse)
• Mexiletine (Mexitil)
• Pentoxifylline (Trental, etc.)
• Deferasirox (Exjade)
• Tacrine (Cognex)
• Thiabendazole (Mintezol)
• Ticlopidine (Ticlid)
• Zileuton (Zyflo, etc.)

Comment:

Inhibitors of CYP1A2 (and to a lesser extent CYP3A4) may increase serum theophylline concentrations; some patients may develop theophylline toxicity. These inhibitors appear to have less risk of serious theophylline toxicity than the Class 2 theophylline drug interactions above.

Class 3: Assess Risk & Take Action if Necessary

• Consider Alternative: Use an alternative to the enzyme inhibitor if possible.
• Cimetidine: Although the cimetidine-theophylline interaction is usually modest, an alternative is preferable. Famotidine (Pepcid), nizatidine (Axid), and ranitidine (Zantac) have minimal effects on drug metabolism.
• Monitor: Monitor for altered theophylline response if a CYP1A2 inhibitor is initiated, discontinued, or the dose is changed. Evidence of theophylline toxicity includes nausea, vomiting, diarrhea, restlessness, irritability, and insomnia. Higher serum concentrations can result in cardiac arrhythmias or seizures.