MOA: blocks phosphodiesterase causing increase cAMP which promotes release of epinephrine from adrenal cells. This results in bronchodilation, diuresis, CNS and cardiac stimulation.
Tx range: 5-15 mcg/mL (peak level)
Drug interactions: MANY; MAJOR substrate of 1A2 and 3A4, follows Michaelis-Menten (saturable) kinetics (similar to phenytoin and voriconazole)
- Increase theophylline levels due to 1A2 inhibition: OCs, zafirlukast, zileuton, acyclovir, cimetidine, ciprofloxacin, ethinyl estradiol, fluvoxamine, isoniazid
- Increase theophylline levels due to 3A4 inhibition: amiodarone, azole antifungals, clarithromycin, cyclosporine, erythromycin, diltiazem, verapamil, lovastatin, simvastatin, atorvastatin, PI's, etc.
- Increase theophylline levels due to other mechanisms: allopurinol, erythromycin, propranolol, ephedrine, and possibly w/ other systemic bronchodilators (and possibly phenylephrine, pseudoephedrine)
- Decrease theophylline levels: carbamazepine, phenobarbital, phenytoin, primidone, rifampin, ritonavir, tobacco/marijuana smoking, St. John's wort, tipranavir/ritonavir, high protein diet, low carb diet, thyroid hormones
- Theophylline will decrease lithium (theophylline will increase renal excretion of lithium) and will decrease zafirlukast