Initial duloxetine prescription dose and treatment adherence and persistence in patients with major depressive...

Adherence and persistence with medication therapy are important in the management of major depressive disorder. This study examined the association between initial prescription dosage of duloxetine and its adherence and persistence. In a large commercial managed-care claims database, 6132 patients with major depressive disorder were initiated on duloxetine between 1 July 2005 and 30 June 2006 at low dose (<60 mg/day, n=1989), mid dose (60 mg/day, n=3733), or high dose (>60 mg/day, n=410). Adherence was defined as medication possession ratio more than or equal to 0.8, and persistence was defined as the length of therapy without exceeding a 15-day gap. Over a 6-month period after duloxetine initiation, mid-dose initiated patients had a higher adherence rate (42.2%) than low-dose (35.6%, P<0.001) or high-dose initiated patients (36.1%, P<0.001). Mid-dose duloxetine-initiated patients stayed significantly longer with the medication (107.3 days) compared with low-dose (95.8 days, P<0.01) or high-dose patients (95.4 days, P<0.01). After adjustment for baseline demographics, comorbid conditions, and prior medications, mid-dose initiated patients remained to have better adherence and longer persistence than low-dose or high-dose initiators. The findings suggest that patients initiated with a dose of 60 mg/day of duloxetine seem to be more adherent to and persistent with the medication than those initiated with less or more than 60 mg/day.