During the identification period of January 1, 2000February 28, 2001, a total of 11,298 patients were newly prescribed one of two antidepressant drugs ( Table 1 ). Of the total, 68.3% (7719 patients) were newly prescribed fluoxetine and 31.7% (3579 patients) were newly prescribed venlafaxine XR. Mean ± SD age of the total cohort was 46.8 ± 15.6 years; 73.5% were women, and 17.8% were Medicare+Choice plan members. Compared with patients newly prescribed fluoxetine, those newly prescribed venlafaxine XR were on average significantly older (46.2 ± 15.2 vs 48.2 ± 16.3 yrs, p<0.0001), less likely to be female (75.8% vs 68.6%, p<0.0001), and more likely to be members of Medicare+Choice (15.9% vs 21.7%, p<0.0001).
Within the venlafaxine XR and fluoxetine groups, 61.4% and 67.8%, respectively, of members filled one or more prescriptions of their index antidepressant therapy and did not switch to another antidepressant during the follow-up period. In addition, 25.6% and 22.3%, respectively, had only one fill of their index drug. The remainder (12.9% and 9.8%, respectively) of the patients switched to another antidepressant during the follow-up period. For both groups of patients, most prescriptions for venlafaxine XR or fluoxetine were written by physicians with a specialty other than psychiatry. The final cohort analyzed consisted of 7430 members who did not switch therapy and had at least one refill of their index drug. The results presented in subsequent sections refer to this subset of patients.
For patients in the fluoxetine-only group, the average index daily dose was 24.8 ± 14.6 mg, with 60.5% of the patients receiving 20 mg/day. In comparison, the average index daily dose for patients in the venlafaxine XRonly group was 111.4 ± 66.7 mg, with 50.2% of the patients receiving 75 mg/day. For both groups, the daily dose in general increased with days of therapy, ranging from a mean of 24.326.8 mg/day for fluoxetine and 108.5123.5 mg/day for venlafaxine XR.
To examine continuous treatment and treatment adequacy, only the 7430 patients who did not switch therapy and had at least one refill of their index drug were included. For both antidepressant groups, the proportion of patients with 84 days of continuous treatment was higher than that with 180 days of continuous treatment within each of the antidepressant cohorts ( Table 2 ). A similar trend was observed for adequate trial of 84 and 180 days. In addition, patients newly prescribed venlafaxine XR reported higher continuous treatment and adequate trial of 84 and 180 days compared with those newly prescribed fluoxetine.
Patients who received only venlafaxine XR were significantly more likely to have 84 (72.4% vs 64.8%, p<0.0001) and 180 days (47.9% vs 43.0%, p=0.0001) of continuous treatment than those who received only fluoxetine during the follow-up period ( Table 2 ). Similarly, the venlafaxine XRonly group had a statistically significantly higher proportion of patients receiving adequate trial of 84 days (78.7% vs 57.3%, p<0.0001) and 180 days (77.1% vs 51.9%, p<0.0001) than the fluoxetine-only group.
Patients with physicians with a specialty other than psychiatry were 2.7 times (95% CI 2.23.3) more likely to have adequate dosage at 84 days than patients being treated by psychiatrists. Patients with physicians with an undetermined specialty other than psychiatry were 1.6 times (95% CI 1.32.0) more likely to have adequate dosage at 84 days than patients being treated by psychiatrists. Similarly, patients with three-tier or open pharmacy benefits were 1.5 (95% CI 1.31.7) and 1.3 (95% CI 1.01.6) times more likely, respectively, to have adequate trial of 84 days than those with managed plans. In addition, patients in the venlafaxine XRonly group were 3.1 times (95% CI 2.63.5) more likely to have adequate trial of 84 days than patients in the fluoxetine-only group (Figure 1).
Adjusted odds ratio and 95% confidence intervals for achieving treatment adequacy (i.e., adequate dosage) at 84 days or 180 days. Comparisons are with venlafaxine XR versus fluoxetine; women versus men; other specialty versus psychiatry specialty; three-tier pharmacy benefit (list of formulary and nonformulary drugs with increasing copayments) versus managed pharmacy benefit (list of formulary and nonformulary drugs [nonformulary drugs are not reimbursed unless medically necessary by prior authorization]); open pharmacy benefit (reimbursement of all drugs prescribed) versus managed pharmacy benefit. Age groups were also included as covariates (not shown).
The logistic regression model was constructed to examine adequacy of dosage at 180 days, applying the same covariates. All variables except sex were significantly associated with adequate trial of 180 days (p<0.0001). Patients younger than 65 years were 2243% less likely to have adequate trial of 180 days than those older than 65 years. With respect to index prescriber and pharmacy benefit, odds ratios similar to those of 84 days of adequate trial were observed. At 180 days, patients in the venlafaxine XRonly group were 3.6 times (95% CI 3.04.2) more likely to report adequate trials than patients in the fluoxetine-only group (Figure 1).
Pharmacotherapy. 2004;24(1) © 2004 Pharmacotherapy Publications
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Cite this: Acute and Continuation Treatment Adequacy With Venlafaxine Extended-Release Compared With Fluoxetin - Medscape - Jan 01, 2004.