A clutch of generic firms, apart from Dr Reddy's Laboratories, are rolling out fluoxetine in different dosages in the US, following approval from the US regulators on Thursday for the generic versions of Eli Lilly & Co's Prozac (generic name is fluoxetine).
Barr Laboratories Inc, which went through an exhaustive legal process with Eli Lilly, is launching 20 mg capsule of fluoxetine.
Barr expects to have 180 days market exclusivity for its 20 mg capsule as the only generic seller of that form, which accounts for about $2.2 billion of Eli Lilly's $2.7 billion annual sales of Prozac.
A unit of Merck of Germany has received US FDA approvals for the 10 mg and 20 mg tablet forms of Prozac.
Teva Pharmaceutical Industries Ltd has also received approval for a liquid oral formulation with a dose of 20 mg per 5 ml.
Geneva Pharmaceuticals Inc, a unit of Swiss drug giant Novartis AG, received the go-ahead for a 10 mg. capsule generic version.
All these firms have also received 180 days of generic marketing exclusivity for their respective dosage forms as they have had received approvals first.
A 30-day supply of 20 mg Prozac capsules costs about $80-95 in the US. But Barr's version is expected to be priced about 30 per cent lower.
The price of floxetine dosages is likely come down much further in about six months, when more knockoffs of the main dosage form are permitted to be sold.
Major branded drugs typically lose up to 80 per cent of their annual revenues within a year after facing competition from generics.
Prozac, launched in the US in 1988, was the first among the revolutionary new class of anti-depressants called selective serotonin reuptake inhibitors (SSRIs).
These drugs coax serotonin, a brain-messenger chemical, to remain in spaces surrounding nerve endings, instead of moving into nerve endings -- a process believed to stave off depression symptoms.
Though some anti-depressant SSRIs were launched, including GlaxoSmithKline's Paxil and Pfizer Inc's Zoloft, Prozac has emerged as the best seller.
More than 38 million patients are expected have taken Prozac since its launch and it is sold in over 100 countries. More than 85 per cent of Prozac's annual sales of $2.7 billion comes from the States.
Prozac was named product of the century by Fortune magazine in 1999, but its sales slipped 2 per cent in 2000 largely due to the impact of first-time generic competition in the UK.
After losing its case in the district court, Eli Lilly plans to appeal in the US Supreme Court, but legal experts said the higher court is unlikely to take up the case.
