Carlson won the business after pitching against four undisclosed agencies.
The account was previously spread out across a number of agencies. Carlson has already been working with UniChem for two years on its conferencing and research initiatives.
UniChem is one of Europe's main distributors of pharmaceutical, healthcare and well-being products, and services its own retail pharmacies as well as independent pharmacies.
The agency will initially be developing marketing initiatives for retail and marketing services.
Carla Reeves, UniChem marketing controller, said: "We needed a broader, more consolidated agency offering in order to achieve our business objectives.
"Through our experience with Carlson, we know the agency is ideally suited to handle all aspects of the marketing mix and we look forward to Carlson helping us move our business forward."
UniChem serves around 5,700 independent pharmacies and hospitals.
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