India-based Sun Pharmaceutical Industries has completed the merger with Ranbaxy, as part of a $3.2bn deal.
Sun has started integration of the acquired business that allows the firm to become the fifth largest specialty generic pharmaceutical business across the globe.
Sun Pharma chairman Israel Makov said: "The combined entity will capitalise on the expanded global footprint and enhance our dominance as a world leader in the specialty generics landscape.
"The firm now includes a wide range of specialty and generic products, comprising chronic and acute prescription drugs."
"Sun remains committed to uncompromised product quality, 100% compliance and promotes innovation to create the most dynamic global specialty generics pharmaceutical company."
Under the deal that was first announced in early April 2014, Ranbaxy shareholders received 0.8 share of Sun Pharma for each share they own.
As a result of the merger, Daiichi Sankyo turns into the second largest shareholder in Sun Pharma and both firms will work together to strengthen their global business.
The integrated company will have operations in five continents and products will be sold in around 150 countries with a strong market share in the US, India, Asia, Europe, South Africa, CIS & Russia and Latin America.
The firm now includes a wide range of specialty and generic products, comprising chronic and acute prescription drugs.
Sun Pharma managing director Dilip Shanghvi said: "We will continue to focus on gaining trust of the Regulators globally, while continuing to develop products based on patient needs and leverage them to become brand leaders globally."
In February this year, Sun obtained approval from the US Federal Trade Commission (FTC) to acquire Ranbaxy.
The Competition Commission of India (CCI) granted approval for the acquisition in early December 2014.