Novartis’ withdrawn irritable bowel syndrome drug Zelnorm is to make a return to the US market but only as part of a restricted access programme for women under 55.

The US Food and Drug Administration has announced that it is permitting the restricted use of Zelnorm (tegaserod maleate) to treat IBS with constipation and chronic idiopathic constipation in women younger than 55 who meet certain conditions. However, the product is being treated as an investigational new drug and “ patients must meet strict criteria and have no known or pre-existing heart problems and be in critical need of this drug”, said Steven Galson, director of the FDA's Center for Drug Evaluation and Research.

He added that "Zelnorm will remain off the market for general use", in line with its status since March in the USA when the FDA asked Novartis to suspend marketing of the drug, known as Zelmac elsewhere, after the firm notified the agency about a retrospective analysis of data from more than 18,000 patients on its clinical trial database. That data showed that cardiovascular events occurred in 13 out of 11,614 patients treated with Zelnorm, compared to one case in 7,031 placebo-treated patients.

The Swiss major said that it was "moving forward with this programme” with the FDA “because of requests from physicians and patients" after sales of the drug were suspended. 20 other countries have followed the USA’s example of taking the drug off the market but Novartis has always maintained that no causal relationship between Zelnorm and cardiovascular ischemic events has been demonstrated.

The Basel-headquartered firm added that it has extensively studied Zelnorm “and believes that this medicine provides important benefits for appropriate patients”, noting that it is in discussions with the FDA “to better understand the findings and to determine appropriate next steps”. The drug was a big earner for the firm, bringing in $561 million in 2006, but its first-half 2007 sales fell 66% to $91 million and the fall-out from the suspension, plus generic competition to its blood-pressure-lowering drug Lotrel (almodipine/benazepril) and the antifungal Lamisal (terbinafine) has led to Novartis reducing its full-year earnings estimates.