Teva Pharmaceutical Industries is expected to win antitrust approval from the European Commission for a $40.5bn (£28.5bn) bid for Allergan's generics unit.
If the deal is closed, Allergan will receive $33.75bn in cash and shares of Teva valued at $6.75bn.
The deal is set to get the go-ahead from the European Commission after Teva agreed to sell off some of its products to appease regulators, Reuters reports.
Read more: Pfizer and Allergan seal the $160bn deal
To address competition concerns, Teva will dispose of some drugs that are already on the market and others that are in the pipeline. Sources had previously said assets worth around $1bn in the US, Europe and Middle East would be sold to win approval.
Teva, Allergan and the European Commission – which is scheduled to decide on the case tomorrow – declined to comment.
The deal also requires US approval and triggered a warning from the American Antitrust Institute in January.
A letter said: "Potentially adverse effects could be large since generic sellers introduce a critical measure of competition into pharmaceutical markets and play an important competitive role in making prescription drugs affordable.
"Any limitation or diminution of the competitive influence of generic pharmaceutical firms could therefore have substantial adverse consequences."
At the end of last year, Pfizer and Ireland-based Allergan agreed the biggest pharma deal ever, a $160bn merger.