The drug Zofran is quite commonly known by its chemical name, which is ondansetron. This substance was invented in the early 1980s in England by an affiliate of its maker in the US, which is GlaxoSmithKline (GSK). That company obtained a US patent for ondansetron in 1987 and another in 1988.
These patents gave GSK the right to exclusively market and sell this drug in this country until December 2006. The FDA approved Zofran (initially for intravenous use, then as an injection, and still later in pill form) beginning in January 1991. After enjoying 15 years of the exclusive right to market and sell Zofran, generic ondansetron became available in the United States in approximately July, 2007. Teva Pharmaceuticals USA and SICOR Pharmaceuticals were the first companies in this country to be granted FDA approval. Several other generic makers have since received similar approval.
Prior to generic ondansetron entering the market, Zofran ranked as the 20th highest selling brand name drug in the U.S. In the first nine months of 2006 alone, sales of Zofran reached $1.3 billion dollars. It is not known how much of these sales were for off-label (i.e., unapproved) use in expectant mothers. What is known, however, is that Zofran (ondansetron) became the most frequently prescribed antiemetic (prevention of vomiting) drug among pregnant women in the United States.
The only purposes for which the FDA has ever approved Zofran are 1) prevention of nausea and vomiting associated with initial and repeat courses cancer therapy, and 2) prevention of postoperative nausea and/or vomiting. GSK has never asked for or received FDA approval of Zofran for treatment of morning sickness in pregnant women.
The only data GSK has ever submitted to the FDA to suggest Zofran did not cause birth defects were four small 30 year-old experiments in rats and rabbits. The results of these animal tests were not very reassuring. For more on this, please see our related post entitled “Rats, Rabbits, and Zofran.”