Drug Interactions between doxepin topical and Duo-Medihaler

MONITOR: Coadministration of beta-2 adrenergic agonists with other adrenergic agents may potentiate the risk of cardiovascular side effects. Beta-2 adrenergic agonists can produce clinically significant cardiovascular effects including increases in pulse rate and systolic or diastolic blood pressure as well as ECG changes such as flattening of the T wave, prolongation of the QTc interval, and ST segment depression. The risk is lower when beta-2 adrenergic agonists are inhaled at normally recommended dosages. However, these effects may be more common when the drugs are administered systemically or when recommended dosages are exceeded.

MANAGEMENT: Caution is advised if beta-2 adrenergic agonists are used concomitantly with other adrenergic agents, particularly in patients with cardiovascular disorders such as coronary insufficiency, cardiac arrhythmias, hypertrophic obstructive cardiomyopathy, or hypertension. Blood pressure and heart rate should be closely monitored.

MONITOR: The concomitant use of isoproterenol and tricyclic antidepressants may increase the risk of arrhythmias, especially at high doses. The mechanism has not been delineated. Tachycardia has been reported in clinical studies. Rare cases of malignant cardiac arrhythmias have also been reported in patients who took oral isoproterenol and tricyclic antidepressants; however, causality was not clearly established due to excessive doses ingested and the presence of other drugs.

MANAGEMENT: Some authorities suggest that the initial rate and dose of isoproterenol should be reduced in patients taking tricyclic antidepressants, and then titrated, as is usual according to clinical response to avoid the risk of developing hypertension or arrhythmias. Patients receiving this combination should be monitored and advised to notify their physician if they experience a fast or irregular pulse.