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Alprazolam-XR Appears to Have Same Speed of Onset as Alprazolam-CT: Presented at ADAA

By Jerry Ingram

MIAMI, FL -- March 16, 2004 -- Alprazolam extended release (Xanax XR) appears to have the same speed of onset as the older formulation of alprazolam-CT, according to research presented here on March 13^th at the Anxiety Disorders Association of America 24^th Annual Conference.

"The central question addressed is should Xanax XR be used as a rescue medication or should it be used as a prophylaxis for treatment," said David V. Sheehan, MD, MBA, Professor and Director, Office of Research, Department of Psychiatry and Behavioral Medicine, University of South Florida College of Medicine, Tampa, Florida, United States. "For after all if it's delayed release, the expectation is that it would have a delayed onset."

For this investigation, Dr. Sheehan and his team conducted a 9-week, open label, switch study including 30 patients who were diagnosed with panic disorder according to Diagnostic and Statistical Manual – Revision IV criteria. Patients were initially treated with alprazolam-CT for 3 weeks, with patients taking medication 3 to 4 times per day, and then changed to a comparable dose of alprazolam-XR in week 4. The mean dose was 4.6 mg/day.

Patients were followed and evaluated over an additional 6-week period. After each dose, researchers conducted hourly measures of the benefit that patients experienced on a scale of 0 to 10. The clinician in consultation with the patient graphed a summary of this data at the end of each week. In addition, they used paired t-tests to compare the magnitude of benefit, the peak benefit and the time to benefit before and after the patient's conversion to alprazolam-XR.

The magnitude of benefit at the first hour after the first morning dose was similar before and after the conversion to alprozolam-XR (6.8 vs. 6.9). Peak benefit was also similar to that reported with alprozolam-CT (7.3 vs. 7.6) with no significant differences in mean time to peak benefit (1.5 hours vs. 1.6 hours).

"What we found was that measuring at hourly intervals after the morning dose, that XR seemed to kick in and have a magnitude of benefit after 1 hour exactly the same as the old formulation and therefore Xanax XR can be used as a rescue medication just like the old formulation," Dr. Sheehan said. "On the other hand, it has a prolonged duration of action, working for 12 hours."

The researchers concluded that alprazolam-XR may be used as a rescue medication and could be preferred over the older formulation for treatment of panic disorder. However, they caution that more study is needed to confirm these findings in light of the small size of the patient population in this particular study and the inherent limitations of self-reports.


[Study title: The Speed of Onset of Action of Alprazolam-XR Compared to Alprazolam-CT in Panic Disorder. Abstract 27]

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