Two local pharmacy giants have unveiled multi-billion-dollar merger plans.

Chemmart and Terry White Group (TWG) will merge to form a retail juggernaut with around 500 stores and $2 billion turnover nationwide.

New Zealand-based medical and pet care firm EBOS will sell Chemmart to for a 50 per cent stake of the merged entity.

EBOS CEO Patrick Davies will be on the board of the merged group.

Chemmart's current executive director will be the chief operating officer of the merged firm.

EBOS has been around for a long time, starting off selling lamps for horse-drawn carriages as the Early Brothers Trading Co in 1922.

Through the lens of history it is easy to tell the Early Brothers made a good choice by diversifying into medical wholesale.

EBOS now brings in revenues above NZ$6 billion a year across its medical supply, healthcare, chemist and pet care operations.

Terry White chief Anthony White will run the merged group, and has welcomed the extra scale and capital EBOS will bring.

“The merger of the two networks creates a comprehensive national footprint and increased scale which, when combined with capabilities across retail, merchandise and private label, will improve the group's competitiveness and front line health service delivery for the benefit of all our pharmacy owners and customers,” White said in a statement.

“We have a substantial array of core retail capabilities and support platforms which are scalable to handle this growth and support future network expansion.”