Montelukast Theophylline

II. BRONCHODIIATORS - montelukast, theophylline 12. CARDIAC GLYCOSIDES -digitoxin 13. CALCIUM CHANNEL BLOCKERS - felodipine, nifedipine, nimodipine, nisoldipine, verapamil... 

Administration of zafirlukast and aspirin increases plasma levels of zafirlukast, When zafirlukast is administered with warfarin, there is an increased effect of the anti coagulant. Administration of zafirlukast and theophylline or erythromycin may result in a decreased level of zafirlukast. Administration of montelukast with other drugs has not revealed any adverse responses. Administration of montelukast with aspirin and NSAIDs is avoided in patients with known aspirin sensitivity. Administration of zileuton with propranolol increases the activity or the propranolol with theophylline increases serum theophylline levels and with warfarin may increase prothrombin time (PT). A prothrombin blood test should be done regularly in the event dosages of warfarin need to be decreased. 

Zafirlukast and montelukast are well tolerated. Zafirlukast increases plasma concentrations of warfarin and decreases the concentrations of theophylline and erythromycin. In rare cases, treatment of patients with CysLT receptor antagonists is associated with the development of Churg-Strauss syndrome, a condition marked by acute vasculitis, eosinophilia, and a worsening of pulmonary symptoms. Because these symptoms often appear when patients are given the leukotriene receptor antagonists when they are being weaned from oral corticosteroid therapy, it is not clear whether they are related to the action of the antagonists or are due to a sudden reduction in corticosteroid therapy. 

Treatment with a leukotriene-receptor antagonist, particularly montelukast, is widely prescribed, especially by primary care providers. Taken orally, leukotriene-receptor antagonists are easy to use and appear to be used more regularly than inhaled corticosteroids. They are rarely associated with troublesome side effects. Maintenance therapy with a leukotriene antagonist or with cromolyn or nedocromil appears to be roughly as effective as maintenance therapy with theophylline. Because of concerns over the possible long-term toxicity of systemic absorption of inhaled corticosteroids, this maintenance therapy is widely used for treating children in the USA. 

Theophylline [the OFF i lin] is a bronchodilator that relieves airflow obstruction in chronic asthma, and decreases the symptoms of the chronic disease. Previously the main-stay of asthma therapy, theophylline has been largely replaced with (3-agonists and corticosteroids. Theophylline is well absorbed by the gastrointestinal tract, and several sustained-release preparations are available. The drug has a narrow therapeutic window, and an overdose of the drug may cause seizures or potentially fatal arrhythmias. Further, theophylline interacts adversely with many drugs. See pp. 450-451 for a description of newly approved drugs, zileuton, zafirlukast, and montelukast. 

Montelukast does not appear to alter theophylline levels. A single case report describes a rapid rise in theophylline levels in a patient given zaflriukast. Zaflriukast ievels are modestly reduced by theophylline, but this does not appear to be clinically important. 

In a study in 16 healthy subjects, the pharmacokinetics of a single intravenous dose of theophylline were not significantly changed by montelukast 10 mg daily for 10 days, but when they were given montelukast 200 mg and 600 mg daily, the AUC of theophylline was reduced by 43% and 66%, respectively. These doses are 20 and 60-fold higher than the usual 10 mg daily dose, and therefore the clinical relevance of these effects is unclear. 

Information about interactions between theophylline and montelukast seems to be limited. The study above indicates that when using normal clinical doses of montelukast no special precautions or dosage alterations are needed. Similarly, no adverse interaction would normally seem to occur with zaflriukast and theophylline the isolated case is of doubtful general significance. 

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