Teva's purchase of Allergan's generics business has been cleared by US antitrust authorities after the company agreed to divest 79 of its generic drugs.

The Federal Trade Comission (FTC) ruled that the $40.5 billion deal could only go ahead if Teva sold the rights and assets related to these drugs to 11 rival firms – the largest ever divestiture order in an FTC pharmaceutical merger case.

These firms are: Mayne Pharma Group, Impax Laboratories, Dr. Reddy's Laboratories, Sagent Pharmaceuticals, Cipla, Zydus Worldwide DMCC, Mikah Pharma, Perrigo Pharma., Aurobindo Pharma USA. Prasco and 3M Company

"Millions of Americans rely daily on generic drugs to treat a wide range of illnesses," said Debbie Feinstein, Director of the FTC's Bureau of Competition. "The FTC's settlement safeguards the competitive availability of these medications for patients across the country who depend on them."

Israel-based Teva, is the largest generic pharmaceutical producer in the world. Allergan is also a global producer of generic, branded and over-the-counter pharmaceuticals, and the third largest generic in the US. Teva expects to finalise the deal next week.