Once-weekly dosing of fluoxetine in the maintenance of remission in panic disorder

Background: Fluoxetine and its active metabolite norfluoxetine have long half-lives of 4-6 days and 4-16 days, respectively. We postulated that, owing to the long elimination half-life, patients diagnosed with panic disorder might be maintained on fluoxetine taken once a week, after being treated initially with daily doses of fluoxetine. Method: Ten patients with DSM-III-R panic disorder were treated openly with fluoxetine, 20-40 mg daily. Once panic free, these patients were switched to once-weekly dosing of fluoxetine, and dosage was titrated as needed. Results: All 10 patients successfully switched to once-weekly dosing. One patient reported recurrence of panic attacks 18 months after the switch. After a brief treatment for 4 weeks with benzodiazepines and daily fluoxetine, the patient was once again maintained on once-weekly dosing when rechallenged. Patients have been maintained in a panic-free state for up to 26 months with a single weekly dose of fluoxetine ranging from 10 to 60 mg. The medication was well tolerated. Conclusion: Fluoxetine at doses ranging from 10 to 60 mg administered once weekly appears to be effective maintenance treatment for patients with panic disorder who were initially treated successfully with daily fluoxetine. A once-weekly regimen may allow for considerable cost savings and may serve as a convenient alternative method for treating panic disorder.