Fluoxetine hydrochloride (Prozac) will become the only antidepressant available in a once-a-week formula if the FDA approves the new application filed by Indianapolis-based Eli Lilly and Company last month.

The new version will come in a dose up to seven times the current 20 mg capsule but with a delayed-release mechanism.

"The capsule is coated with enteric beads that slow the entry of the drug into the blood stream at a rate that maintains the desired effect," according to Rajinder Judge, M.D., director and global physician for Prozac at Lilly Research Laboratories in Indianapolis.

"We wanted to give patients who need long-term maintenance therapy a choice. This gives them the psychological advantage of being able to control their depression without being reminded daily that they are ill," said Judge.

She noted that a concern is whether patients will remember to take their capsule once a week. "Our study showed that patients were slightly more likely to take their capsules once a week than once a day," said Judge.

She added that the tolerability profile of the high-dose capsule is very similar to that for the 20 mg capsule.

Judge said the FDA approval process could take up to a year. Lilly has also sought approval from regulatory bodies overseas, including those in Britain and Spain, to distribute the once-a-week formulation of Prozac.