Shares in Reckitt Benckiser were hammered on Monday by the news that it has lost exclusivity over its SUBOXONE tablets after the Food and Drug Administration (FDA) gave two drug manufacturers the green light to produce generic versions of the drug.

The RB Pharmaceuticals business (RBP) had filed a 'Citizen's Petition' to the FDA to raise the barrier to generic versions of the product, which is used in the treatment for the chronic diseases of addiction.

RBP had called for more stringent packaging standards and increased educational interventions to help lower the number of children exposed to products that contain buprenorphine - found in RBP's SUBOXONE tablets - which is used to treat opioid dependence.

Reckitt announced on Monday morning that the FDA had denied its petition, saying that existing labelling and safety programmes were "sufficient". As such, the regulator approved two generic versions of the tablet in the US, which accounted for around 5.0% of group profits last year, according to analyst Martin Deboo from Investec.

Meanwhile, analysts at Jefferies estimate that these generics "could enter the market within a month". They said that this would cut around 3.0% off full-year earnings at Reckitt and around 8.0% shed from 2014 earnings.

The broker said: "Whilst the possibility of generic entry has been a well-flagged risk for the Reckitt investment case for some time, we believe that the market had become somewhat complacent of the risks, and indeed that a number of investors had gradually come around to the view that generics would never enter the market.

"On this basis, we would expect the shares to tick down as the market gradually digests the impact of this news over the coming days."

Shares were down 3.01% at 4,380p before the close of trade in London.

Reckitt disappointed

The company said that it is "disappointed" with the decision but will continue to work with the FDA on safety enhancements.

"RBP remains committed to maintaining its own high level standards for safety, including the use of child resistant, unit-dose packaging for its buprenorphine-based opioid dependence treatment products.

"It will therefore carry on with the decision to discontinue the sale of its loose tablet bottles of SUBOXONE in the United States in favour of other effective treatment options that have shown reduced paediatric exposure rates."

Reckitt makes a wide range of household cleaning products such as Cillit Bang and Calgon, but is also responsible for brands such as Nurofen and Strepsils.

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